This FAQ is the product of my research and individual experiences. All contents are copyright © 2001-2006 Ronald Parr. While this is a sincere effort to give you the best and most accurate information possible, some biases and inaccuracies may slip in. I make no apologies for this. Your experiences may differ, your mileage may vary, etc.
The FAQ is organized into 12 sections. Please keep in mind that the section topics are not completely disjoint, so if you are having trouble finding something, be sure to check related sections too.
I'm Ron Parr. You can email me at "ronparr - at - yahoo.com". (You'll need to convert that to a proper email address.) Feel free to email corrections or suggestions. I probably won't be able to answer individual questions though. That would be a full time job!
So, you want a resumé? If only people approached everything else they read on the Internet with such skepticism! I'm a computer science professor, but digital photography is just a hobby. I won't pretend to be an authority on most of these topics; they're just things I've picked up over the past few years.
My interest in photography began when I was a teenager, but I did not pursue it as intensely as I might have liked because of the time investment and slow learning cycle associated with traditional chemical photography. When digital photography began to mature, I immediately recognized that it would remove the main obstacles to my pursuit of photography when I was younger, and I followed the field with interest. In 1999, I concluded that the new generation of 2 MP digital cameras were at a sufficient level of maturity to yield high quality images and give the photographer enough control to make things interesting.
My first digital camera was a Nikon CoolPix 950. Since then, I have owned a Sony DSC-S85, Canon D30, Canon D60, Canon S400, Canon 20D, and Canon SD500.
As a regular visitor on dpreview and (digital) camera expert among my circle of friends and family, I found that the same questions kept coming up over and over again. I wasn't aware of a single resource that answered many of these questions, so I started creating this FAQ. It has taken a good bit of my spare time, but I find that it has served a useful purpose of helping me organize both my thoughts and my links. Hopefully, it will be useful to you too.
In the most general sense, almost all of the knowledge here comes from things I've learned from scouring the web for the past few years. The entire global community of photography aficionados deserves some credit and thanks for this. The smaller communities at dpreview played a huge role in this too, first the Nikon talk forum, then the printer forum and most recently the Sony talk forum.
Many individual members of the Sony talk forum have made specific points or suggestions that have found their way into this FAQ. Shay and Ulysses come to mind immediately. The others whom I am forgetting to mention also get my thanks - and apologies.
Part of what makes the FAQ interesting for me and useful for other is, I think, that it's a living document. It's constantly evolving and contains many links that people can follow to get more information. I'm afraid that it would lose some of this appeal in printed form.
I no longer own a Sony camera and many of the questions and answers in that section were becoming outdated. I removed a few very outdated parts, then generalized the remaining questions and transferred them to the more general parts of the FAQ.
Here are some general guidelines for taking good portraits:
OK, nobody asked this one, but I couldn't resist:
I'm not an attorney and would encourage you to consult one if this is a serious concern for you. The following site does attempt to address some of these questions (be sure to check the links at the bottom too): Travel Photography and The Law.
Some other references:
It sounds like what you want is a neutral density filter. This makes everything a little darker without affecting the colors or the polarization of the light.
Try a polarizing filter, also called a polarizer. If you have an SLR which uses phase detection for autofocus (most do), then you'll need to get a circular polarizer to avoid conflicts with your autofocus mechanism. I haven't tried it myself, but a circular polarizer probably is not necessary with non-SLR digital cameras.
Try a polarizing filter, which can also be used to reduce glare. See above.
A very large number of them (but not all) can be downloaded from Henry's. Henry's seems to have stopped updating this page. Your manufacturer's web page is another good resource.
SLRs typically use phase detection autofocus. This Scientific American article, Focusing in a Flash, makes an attempt to describe phase detection AF, but isn't all that clear. The basic idea is as follows: The AF system grabs strips of image from opposite sides of the lens that nevertheless project onto the same area in the focal plane. (This is typically done by using a half silvered reflex mirror and some optics behind the mirror.) When the overall image is out of focus, these two strips will be shifted in opposite directions, much like an old split prism viewfinder. When the overall image is in focus, the image captured by the two strips will be identical. The AF mechanism has two (or more) separate sensors corresponding to different parts of the lens. The lens is adjusted until these two images are the same, and the overall image is then presumed to be in focus.
Non SLR digital cameras typically use contrast detection AF. While typically slower and less accurate than phase detection, contrast detection is cheaper and simpler. It requires no additional lenses and uses the main sensor only. Contrast detection adjusts the lens until it finds the position that maximizes the contrast measured in a (weighted) region of the main sensor, under the assumption that maximum contrast implies sharpest focus. Contrast detection will hunt around until it finds the point that maximizes contrast.
With adequate light and a well calibrated lens, a phase detection system can, in principle, compare the two images and estimate the direction and amount to move the lens mechanism to achieve accurate focus. In comparison, contrast detection has no way of knowing the maximum achievable contrast in the scene a priori, or determining the direction in which this is achieved. This explains the greater potential of phase detection for fast focusing. (Note that I have described these different mechanisms in general terms. Different manufacturers will undoubtedly have embellishments and improvements on this.)The exposure for a shot determines the amount of light that strikes the film or sensor. There are two variables the control this, the aperture and the shutter speed. These adjustments are required because no film or electronic sensor has yet been developed that can capture the full range of light intensities to which the eye responds. Of course, our eyes have help too. We have pupils which constrict in bright light and dilate in low light.
So, why don't our eyes ever expose things incorrectly? Our pupils tend to adjust to whatever we're focusing on, so we automatically compensate as our gaze moves. (Obviously, a camera can't do this since it must use a single exposure for the entire scene.) However, it is possible to get your eyes to expose things incorrectly: Have one of your friends stand with his back to a very brightly illuminated window in an otherwise dark room. Take a few steps back and try to concentrate on your friend's face. It should look dark to you and you may have trouble making out his or her facial expressions. The reason is that your eye is being tricked by the bright background.
Some experienced photographers can judge exposure accurately simply by looking at the scene. In fact, in the days before light meters, this was the only way to do it. Handheld light meters were the next step, allowing accurate measurements of the light levels for an entire scene or for individual subjects. The metered light level, measured in EV, could then be matched against an exposure table to find aperture and shutter speeds appropriate for the shot.
Modern cameras have light meters built in to the camera. They can automatically select both aperture and shutter speed for you, or you can pick one and let the camera pick the other. Most also offer some kind of fully manual mode, where the exposure meter can still be used to provide guidance on how the camera estimates the scene should be exposed.
Your camera has a built in light meter, which it uses the measure the amount of light in the scene at various places. The position of the light meter will vary from model to model. Some popular positions in SLRs are behind the (partially reflective) reflex mirror, or in the pentaprism. On some digital cameras, the main sensor may serve double duty as a light meter.
Your camera will determine the light level in the scene and then use an electronic version of an exposure table to pick the appropriate shutter speed and aperture. You may notice that there are multiple combinations that will be suitable for any EV. To the extent that it is possible, cameras will typically try to pick shutter speeds that are compatible with handheld shooting. The more advanced ones will even take the focal length of your lens into account and try to pick higher shutter speeds if needed to reduce the effects of camera movement.
One thing you should realize now is that with multiple possible combinations of shutter speed and aperture for any exposure level, a one-size-fits-all solution that always chooses one of these many possible combinations can't be right for every situation. This is why more advanced photographers tend to use aperture and shutter priority modes instead of fully automatic.
Aperture priority mode is similar to fully automatic mode, except that you pick the aperture value. Metering works the same way, but with the aperture fixed there is exactly one shutter speed that will provide the correct exposure in the exposure table. This is what the camera picks for you.
There are many reasons for using aperture priority, including:
Shutter priority mode is similar to fully automatic mode, except that you pick the shutter speed. Metering works the same way, but with the shutter speed fixed there is exactly one aperture that will provide the correct exposure in the exposure table. This is what the camera picks for you.
There are many reasons for using shutter priority, including:
This depends upon a number of factors including the focal length, the steadiness of your hands, and vibrations caused by the mechanical parts of your camera, e.g., mirror slap in SLRs. If your lens has a (35 mm equivalent) focal length of X mm, then a good rule of thumb is to shoot at 1/X or faster. Small movements of the camera shift the image more at long focal lengths.
Most cameras will have some subset of the following metering modes: spot, center weighted average (sometimes just called "average", and multi-segment (sometimes called "evaluative").
Spot metering is the easiest to understand: The camera meters only a small area in the center of the frame. This mode is useful if there is a particular area of the frame that you must expose properly, even if it comes at the expense of overexposing or underexposing the rest of the image. Spot metering can be tricky to use properly. If the metered area is quite small, tiny camera movements can have dramatic effects on the metering, making it tricky to get the desired exposure.
Center weighted average metering takes an average over the entire scene, where, as the name indicates, the average is weighted more heavily towards the center. This implicitly makes the assumption that the center is the most important part of the image, but that you don't want to completely ignore the edges of the image either. If implemented properly, this metering mode usually works pretty well. Moreover, with some practice, it will be relatively easy to predict when it will fail and to compensate.
Evaluative metering is the most complex metering method. It samples multiple areas of the frame and tries to come up with a good exposure value that takes all of these areas into account. This can be implemented in varying degrees of sophistication. For example, one implementation might notice two dark blobs with a bright blob in the center, conclude that you are tying to take a picture of two people with backlighting, and adjust the exposure for the people and not the bright background. Such methods can seem to work miraculously when implemented well. The only downside is that they can sometimes outsmart the photographer, making some incorrect assumptions about the effect the photographer is trying to achieve. Thus, some photographers prefer center weighted averaging because they find it more predictable.
This is a way of telling your camera to expose the scene in a slightly different manner from the way the scene was metered. Compensation is usually expressed in terms of the number of stops of compensation and most cameras have the ability to compensate at least between -2 and +2.
Here's an example of how this works: Suppose you dial in +1 compensation. This means that you want the scene to be one stop brighter, which will require a wider aperture, longer exposure, or some combination of these two. If you are using aperture priority mode, your camera will keep the same aperture, but double the exposure time (half the shutter speed). Dialing in a negative value will give you darker images and shorter exposure times (and/or narrower apertures).
It's important to understand that exposure compensation does not change the characteristics of your film or sensor; it's just a way of dealing with situations where the metered exposure isn't what you want.
An SLR is a Single Lens Reflex camera. The single lens part refers to the fact that it is using a single lens for capturing images and displaying on the viewfinder. The reflex part refers to the use of some mechanism for reflecting light towards the viewfinder.
An SLR is a preferred style of camera because it allows the photographer to see exactly what will be captured by the film or sensor without any parallax or distortion. For this reason, high end features have been incorporated into these cameras and the style of camera is sometimes confused with the high end features that go along with it.
Some common misconceptions about SLRs:
For timer shots, many cameras, focus when you press shutter button, not when the timer goes off. Thus, the camera focuses on whatever is in the center of the frame when you press the shutter and will fail to focus on you after you've moved into position in the center of the frame. The workaround is to point the camera at something else which is roughly the same distance from where you plan to be after you move into position. Press the shutter, then quickly adjust the composition and move into place.
In general, high ISO is used in conditions where it is not possible to achieve a fast enough shutter speed with low ISO. Typically, the reason for desiring a faster shutter speed is to avoid blur from motion - either from the camera shake or subject motion. Situations that might require high ISO would include:
Another reason for increasing ISO is to extend flash range. The higher sensitivity will allow you to a less powerful flash for longer distances.
Shop around. I like using pricegrabber to get prices from a large number of retailers at once. Pay careful attention to the merchant ratings column! Also check reselleratings.com.
FWIW, I've noticed that Canoga Camera tends to have very competitive prices on Canon lenses. B & H Photo seems to be well liked be camera by camera aficionados for their good prices and good return policies. Note that some have complained about uneven service and poor packaging, so be sure to read the most recent merchant ratings.
You should definitely read the Camera Confidential PC World article on buying a camera from discount online sellers.
Check their ratings at pricegrabber. You'll find that the least expensive merchants often do one or more of the following tricks:
Check out this posting from a guy who took pictures of some of the Brooklyn store fronts associated with the some of the low cost merchants. It does not inspire confidence.
Not necessarily. A person who has taken some good photos has demonstrated some skill with photography and most likely knows more than a person randomly selected off the street. However, a good photographer will figure out how to take some good photographs with almost any gear. Consumers should be interested in cameras that it will make it easy for them to take good photos in the widest variety of situations. Just because a person can take good photos, doesn't mean that he has insight into this question. Indeed, he may lack insight because he has become so skilled at working around limitations that he has forgotten what issues concern a beginner.
People sometimes comment that only serious photographers need especially good cameras. This was certainly true when "good" meant rugged. If good means that it can be used in a wide variety of situations without heroic efforts or special skill, then beginners need good cameras even more than pros.
Don't be silly. First off, the camera market is extremely competitive and with the exception of esoteric, high end gear, it's not reasonable to expect that any one manufacturer will maintain a consistent edge in consumer gear for many years without being challenged in some way. People who say, "Always buy brand X," are generally people who don't know what they're talking about but bully others into following their lead becasue they're good at sounding very confident when they speak.
Second, digital cameras are a new ballgame in countless ways. Critical parts of the camera, such as the sensor, typically are not made by the same company that puts its name on the camera. For example, Sony makes the CCDs inside the cameras of many competing manufacturers. The cameras themselves are often contract manufactured (Sanyo is as big player in this market), so cameras with different labels may be coming out of the same factory. Finally, one of the most important parts of a digital camera is its electronic innards and image processing algorithms. This is a relatively new product area and there's no reason to think somebody's old prejudices about film cameras are relevant to this in any way.
My favorite place is dpreview. While they don't hit every model, the cameras they do review are covered in a thorough and objective manner, and they offer a clear statement of the strengths and weaknesses of each model. You should keep in mind that the camera market changes rapidly, and that a camera that was "highly recommended" in 2002 may not be a super performer by today's standards.
Other good sites:
The most widely cited place appears to be photodo, which is sadly out of date. photozone also has lens reviews.
A note about lens reviews: There is often significant variation between samples of lenses. Reviews typically consider just a single sample, so you may not get the full picture from reading just a single review.
See also:
The thing to remember about extended warranties is that salesman push them because they are very profitable on average. This means that on average you will lose money with extended warranties. However, there are a few cases where extended warranties can be wise decisions:
If you are seriously considering getting an extended warranty, be sure to read the fine print carefully. Don't believe that particular situations are covered based only upon a salesman's promises.
Every lens has a focal length which is a physical property of the lens. Once the lens is made, this cannot be changed. The field of view associated with a lens will be a function of the area projected by the lens that is captured by the camera. For 35mm film photography, this area is 36mm by 24mm. Note that if you change the area captured, the field of view also changes. For example, using a 50mm lens on an APS format camera yields a very different field of view than using 50mm lens on a medium format camera.
For many years, amateur photographers who used 35mm film and no other systems became accustomed to associating particular focal lengths with particular fields of view. When these photographers moved to other systems, such as medium format, or digital, it was sometimes convenient to think about lens focal lengths in terms of the equivalent field of view they offered in the more familiar 35mm film world.
Note that the 35mm equivalent focal length of a lens is simply a way of relating field of view of a lens attached to a new camera, to the field of view of a different lens attached to a more familiar camera. There is no deeper connection than this.
If you want to check the math on this, I suggest you visit Andrzej Wrotniak's site, which also has some nice tables comparing DOF for different imager sizes. I'll briefly summarize the key points you need to remember:
The effect of small sensors, such as those found in compact digital cameras, on DOF has been a source of great confusion for many. If we think about sensor size in isolation, then it shouldn't have any effect on DOF since a using a smaller sensor is just like cropping a piece of a larger sensor. However, if we want to do a comparison between different systems then we typically want to compare two images that have the same composition and size. To do this, we will need both a shorter focal length lens, and a bigger enlargement for the system with the smaller sensor. The former increases DOF, while the latter decreases it. The effect of using a shorter focal length lens dominates and you get larger DOF in this comparison. See below.
This often cited rule of thumb cannot possibly be right in general, as a simple thought experiment proves: When you have focused your lens at the hyperfocal distance, depth of field extends infinitely far back. If the 2/3 rule were true, then depth of field would need to extend infinitely far in front as well (since 1/3 of infinity is still infinity), and objects behind the camera would need to be in focus. This is obviously ridiculous, so the 2/3 rule cannot be right in general.
How is the circle of confusion (CoC or CoF) determined?For depth of field calculations, the circle of confusion (CoC) is the smallest acceptable amount of blur in the image plane. To determine the CoC, you must do the following:
It's good to understand the depth of field is not well defined without a set of viewing conditions and assumptions about what appears to be in focus. Except for the exact depth at which the camera is focused, everything in the image plane is at some smoothly varying point between perfect focus and total blur. The amount of tolerable blur in the final image determines where you make the cutoff in this continuum between blur and sharpness in the image plane. Without a set of assumptions about how we view images, there would be no way to make this cutoff since everything (except for a 0 thickness plane at exactly the focus depth) is out of focus if we look carefully enough.
For better or worse, there are fairly standardized notions of what is acceptable blur. Typical numbers are about 30 microns in a 24x36 mm (standard 35mm film) frame. If you have a lens with a depth of field scale engraved on the barrel, it was probably computed using a CoC of around 30 microns. You should understand that this is only a rough rule of thumb for what will be in focus in your final print since the lens manufacturer has no way of knowing your viewing conditions or standard of sharpness. Moreover, even if you happen to agree with the viewing assumptions made by your lens manufacturer, you may not be capturing the image on the size medium that was assumed when the lens was made. For example, if you are using a lens with depth of field engravings intended for 35mm film on a camera that has a smaller sensor, the CoC should be reduced (leading to shallower DOF) because a larger magnification is needed to produce the same sized print. (Note that this does not contradict the fact that smaller sensors have more DOF for a given perspective, composition, and f/stop, since achieving these requires the use of a smaller focal length in comparison to a larger sensor.)
Some additional reading:Diffraction is an optical effect that occurs when light passes through a very small opening. Instead of producing a bright, clear image on the other side, it produces a blurry, disc shaped image. (Click here for a more detailed description of the physics behind this.)
Diffraction can reduce the quality of your images when you use very small apertures. Many people think that images always get sharper as you decrease aperture size. This is true up to a point. Beyond this point, they start to get softer due to diffraction.
Probably not. This effect is called vignetting and it is common in consumer quality lenses. If the effect is not equal in all corners, then something may be misaligned and you should return your camera or lens for service.
Some models have been particularly prone to uneven vignetting. For example, a batch of Sony DSC-F707 models had uneven vignetting on their left side, leading to the acronym DLSS (dark left side syndrome). Many owners with this problem ultimately returned their cameras to Sony for service.
From what I have heard, Zeiss people were involved in the design of Sony's Zeiss lenses and they are involved in the manufacture of the lenses too, though the lenses are made in Japan. The extent of the involvement is not clear. Here's a letter somebody received from Zeiss on the topic.
The relationship between Panasonic and Leica seems somewhat different. It is described as a collaboration, although Panasonic's version of events seems to suggest Panasonic engineering and Leica enforcement of quality standards. (Thanks, Diego!)
If you have information about the operation of other Japanese-German partnerships, please let me know.
You are most likely seeing classic chromatic aberration (CA), the details of which are explained in beautiful detail by Van Walree. (See also HyperPhysics or Wikipedia.) In short, chromatic aberration results from the fact that different wavelengths of light refract slightly differently when passing through your lens. This causes some wavelengths to be misfocused, have different magnification and/or get shifted laterally in your image.
See also: How do I correct for chromatic aberration (CA)?
If you don't know what I'm talking about, see: What are those red and green color fringes in my images?
With the lens you currently have, you can reduce CA by stopping down. You may also find that some focal lengths are more prone to CA than others. For zooms, CA is typically worst at one or both of the extreme ends of the range.
Another way to avoid CA is to switch to a different lens. In general, extreme wide angle and extreme telephoto lenses are more prone to CA than "normal" lenses. Zooms are typically more prone to CA than fixed focal length lenses. Lenses with exotic elements (fluorite, high index or low dispersion glass) are less prone to CA. Such lenses are often labeled as "UD" or "ED" lenses. Apochromatic lenses also minimize CA. These are usually labeled as "APO" lenses.
There are several advantages to an external flash:
Red-eye is caused by light from your flash bouncing off of your subject's retina. So, how do you minimize it? There are several approaches:
See tips below on removing red-eye in software.
Some references on red-eye:
If you're wondering about the technical details of how flashes charge and fire, the duration of the flash light, how the effective distance of a flash is calculated, etc., then you must check out Toomas Tam's excellent flash FAQ.
There are several reasons for this. The first is that your flash may be too powerful for shots at such close range. If you have a way to reduce the power on your flash, try this. The second issue is that your flash may not be angled properly to fully illuminate objects at such close range. Your lens may even be blocking some of the light from the flash. You should consider using a diffuser or getting a ring flash, which is a special donut-shaped flash unit that you attach to your camera by screwing it onto the filter threads of the your lens.
Probably, but depending upon your camera's support for standard external flashes, it may require some persistence and some workarounds:
A slave flash is a flash that is triggered by another master flash. You may have noticed event photographers with assistants carrying flashes on poles. These are slave flashes which are triggered by a primary flash on the photographer's camera.
The typical reason for using a slave flash is to illuminate your subject more evenly by providing flash light from multiple sources. There are several approaches to triggering a slave flash. Some have sensors that monitor for a primary burst of flash light and then respond with their own flash. Others are controlled by radio signals from the primary flash.
You need to put some thought and research into the type of slave flash that will be best for you. In principle, slave flashes with sensors are the most versatile and will work with any flash system. However, there is a complication: Some slave flashes can be triggered prematurely be red-eye reduction systems or by preflash metering systems, Canon's E-TTL for example. Before purchasing a slave flash system, it would be wise to check with other users of your primary flash to see what types are compatible.
If you are using your camera in auto mode, it may be choosing a shutter speed that is too low. (This was a definite problem with some earlier Sony models.) This will allow ambient incandescent light in the room to influence the image. Incandescent light is much more yellow than the flash light for which the camera's white balance algorithms are compensating. Thus, images will look more and more red as distance from the flash increases.
You also may be having white balance issues. Check to make sure that your camera is set for the correct white balance, or try adjusting it manually.
One workaround is to use shutter priority mode with a 1/60 or 1/100 shutter speed. This helped improve flash color on some earlier Sony models.
When used in auto mode, some cameras select a shutter speed that is too low for most flash photography. You should consider using shutter priority with 1/60 or 1/100 shutter speed instead if you getting shutter speeds below 1/60.
You may also be attempting to use flash in aperture priority mode. See below...
With many cameras, the camera assumes that you are using fill flash in aperture priority mode. Thus, it picks the correct exposure for the available light and fires the flash merely to fill in shadow areas. On some cameras, you may have workarounds for this:
Unfortunately, for some cameras, such as earlier Sony models, there is no workaround.
You may have a white balance problem. Make sure that you aren't using indoor film, or an indoor white balance setting.
In the case of a Sony DSC-F707, you may have a defective camera that suffers from a problem called Blue Flash Syndrome, or BFS. For more, read here.
A related, but different, problem low called EV BFS (LEVBFS) also afflicted some Sony cameras. The only affects flash white balance in shutter priority mode, and resulted in shots that were too blue. There is no workaround because flash white balance overrides manual white balance on these cameras. Note that if you think your flash shots are too red in auto mode, you may might prefer the bluer cast that results in shutter priority. Things typically get bluer as the shutter speed gets faster, so start with 1/60 and move up.
If you are shooting in auto ISO, your camera may be boosting the ISO to compensate for an underpowered flash. You can try manually forcing the ISO to a lower value, but if the underlying problem is not enough flash power, then you'll get less noisy, but underexposed shots. You might consider getting a more powerful external flash.
Here is an excellent description of how Shay Stephens built an ad-hoc diffuser for his DSC-F707. The basic idea may be generalized to other cameras. (Shay appears to have removed the pictures, but the instructions are still pretty clear.)
Note that when building a diffuser you want to be careful to make sure that you don't accidentally direct energy towards the flash or camera itself, which can cause overheating and damage. Also, be sure to avoid using any materials in your diffuser that could be damaged or could burn when exposed to sudden bursts of heat.
Recent Canon SLRs use a system called E-TTL to determine flash exposure. (Newer models use E-TTL II, which seems to be more robust.) E-TTL is praised by some for allowing very precise control over flash exposure when used properly, but it is slammed by others for being too sensitive to very small changes in the center of the image and requiring too much planning to get proper "automatic" exposure. There is probably some truth in both positions.
Some people are so flummoxed by E-TTL that they prefer to use non-Canon, non-TTL flash units that control exposure with a sensor on the flash.
More resources on Canon flash systems:
E-TTL II is an improvement over E-TTL that is intended to make automatic flash exposure more robust. It includes improved algorithms and the ability to incorporate distance information from compatible lenses.
More on E-TTL II:
For technical issues, my favorites are:
Some other worthwhile sites:
See also Where can I find good camera reviews?
Here are some of my favorites:
If you upload your photos to a photo hosting site, the site will create the gallery for you. If you want to host your own site, then you'll need to find an ISP that provides web space. Once you've done this, you can either learn html and make the gallery yourself, or get some help from a program. Photoshop has a pretty flexible tool built in for doing this. Some other tools:
Avoid the photo gallery tools built in to MGI Photosuite. They make galleries that are incompatible with Unix servers and they use GIFs instead of JPEGs for their thumbnail pictures.
Even if you tell Photoshop not to alter your images when creating the gallery, it recompresses them with high compression when copying them over to the images directory for your gallery. The workaround is to copy and paste your originals into the image folder that photoshop creates for your new gallery.
I have been quite happy with pbase because it is non-commercial (in the sense that it has no ads and doesn't try to sell mugs, prints or other garbage using your photos), and because it contains no language suggesting that you are sacrificing any rights to your photos. If you read the fine print at nearly every other site, you will realize that you are giving up some rights to your photos when you upload them. In my opinion, the fees are reasonable and it is a better deal than sites than bombard you with ads and/or whittle away your property rights through weird loopholes in their terms of service.
Note that smugmug has recently grown to be quite popular because they have no ads and low prices.
Some other sites:
I've stopped adding to this list because I've become aware of a a great Guide To Online Photo Albums which contains detailed info on various sites including their fees and features.
In a word, no. Many of these sites have gone out of business. You should always keep multiple backup copies of your cherished photos. To be extra-careful, you should probably use several types of media and store them in different locations. You should also check their integrity regularly. CD-R media and Zip media don't last as long as you might think: low tens of years at best.
Click on rules/help in one of the forum pages at dpreview and read the part about embedding images. The only tricky part is getting the appropriate URL if you are using an image hosting site like pbase, where you'll need to read the instructions appropriate for your site. In the case of pbase, you'll need to make a contribution to permit external linking.
Don't do something silly like using a URL for a page that displays many other things in addition to your photo. Obviously, this won't work. Also, remember to use the preview button before posting. There is no reason to post a, "This is a test to see if my image shows up," message on dpreview. You can use the preview function to debug your embedding technique.
The most powerful program for editing photos is Adobe's Photoshop. Unfortunately, it's very expensive. The good news is that there is a less expensive version called Photoshop Elements which has nearly all of features of the full version is can be downloaded for a free trial. Avoid PhotoDeluxe. It costs a little less than Photoshop elements, but has much fewer features.
An increasingly intriguing alternative is the The Gimp. The Gimp is a freeware alternative to Photoshop that runs on Windows, Unix and MacOS X. (MacOS info here.) It rivals the power the flexibility of Photoshop, but doesn't cost a cent. There is extensive on-line documentation available too. So what's the catch? This is a complex program and the Windows version may not be completely bug free. The user interface is also very Unix (X11) like, so it might take some getting used to. Still, I think it's worth downloading because it establishes a common denominator, a free cross-platform solution for which people can swap image editing tips. Note: If you having trouble finding somewhere to download macgimp, try osxgnu.
Some other programs:
There is also a large variety of programs and plug-ins that perform very specific manipulations on images:
The short answer: If you are editing the file and plan to reopen it in your image editing program later, you should save it in a lossless format such as TIFF, or one of the other lossless formats supported by your image editor. (See also the discussion of JPEG vs. TIFF below.) If you aren't planning on changing the image at all., you should just leave it in whatever format the camera produced. If you've made some changes and don't expect to do any further edits, you should save in whatever format is appropriate for the final use of the image. (I always save in Photoshop native format just in case.)
The longer answer: There seems to be something of a folklore about lossy compression that defies all common sense and reason. Some people seem to think that resaving an image in a lossless format such as TIFF will somehow improve the quality of the image. This couldn't be further from the truth or from the very meaning of lossless.
Let's start from the beginning: When your image is read off your sensor and processed by your camera, it is represented as a bunch of numbers. To store the file in a format that your computer recognizes, the camera can use 8 bits (= one byte) for each of the red, green, and blue channels used to describe each pixel. Thus, the total size of an image file destined for your computer will be (in bytes) HxVx3, where H and V are the horizontal and vertical resolution, respectively. Notice that this will lead to very large files: A mere 2048x1536 image would require 9 megabytes. Clearly, some form of compression would be very desirable.
Your initial intuitions about compression would probably be to run something like zip on the file to squeeze it down. This would certainly help, but it wouldn't get the file down to a reasonable size for most users. Compression methods like zip, rarely reduce file sizes by more than 50%, and this would still leave us with very big files. The trick is to modify the image slightly in a way that makes it more amenable to compression.
This isn't the place to go into a long discussion of how compression works, but for our purposes we can think of it as trying to find patterns in the data the can be represented much more efficiently than a simple list of all of the pixel colors and intensities. For example (and this isn't really how it works) if your image has a region of blue sky, it could be compressed by indicating the sky color, and the size of the region that has this color, instead of repeating the same numbers over and over again. Unfortunately, there are some problems with this simplistic view of things: Images rarely have regions of exactly uniform color. There are always slight fluctuations that would throw off our compression scheme. The solution involves two parts: 1) performing a mathematical transformation on the image to represent it in a more convenient manner through a set of equations (called a discrete cosine transform) and 2) smoothing over slight fluctuations. In other words, regions of the image that are very close in color and brightness will be treated as if they are the same color and brightness. This helps our compression scheme because it creates larger regions of the same color and the compression becomes more effective. (In truth, the same color and brightness aren't the criteria used. It would be more accurate to say the same low frequency fluctuations in color and brightness. If you don't know what this means, don't worry about it.)
So, what happens when we repeatedly load and save an image using JPEG compression? Each time we recompress the image, we discard a little information about subtle variations in the image and, because of the compression, we can introduce slight defects in the image. As we manipulate the image, these defects may become amplified as we do things such as increasing contrast or brightness. If we resave the image in JPEG, we run the risk of introducing a new set errors into the image and these errors will compound with each resave. In fact, even if we don't change the image, simply resaving it can compound the errors from the previous save.
The way out of this quandary is, after a round of editing, to save your images in a lossless format such as TIFF, or whatever native format your editor supports. When you are storing in a lossless format, you don't introduce extra errors every time you save and load. Of course, this format will take up much more space.
Some common myths about file formats debunked:
Sharpening is a trick to increase the apparent sharpness of an image by increasing the contrast around areas that look like edges in a photo. There are many reasons for doing this, the most obvious of which is that judicious use of sharpening can make a photo more pleasing to the eye. Image resizing also tends to soften edges, so it is often necessary to sharpen an image after resizing. Sharpening should be the last thing you do to an image since the amount and type of sharpening desired will be influenced by everything else you have done to the image. If you sharpen a full size image and then resize, you won't have the appropriate amount of sharpening for your new image size. The amount of contrast and brightness in the image will also affect the amount and type of sharpening you are using, so you should always adjust these before sharpening. The same reasoning applies to essentially every other image modification you can make.
The amount of sharpening you want to apply may also be a function of the output medium on which you choose to display your image. For example, you may want to use more sharpening if the image will be displayed on an old, fuzzy CRT, then if the image is displayed on a new LCD with crisp pixel boundaries.
Most image editing programs have something called a sharpening filter or an unsharp mask. These are a good start and you should experiment with these to develop a feel for how sharpening works. You'll probably notice that flowers tend to stand up well to image sharpening, while portraits do not. You'll also notice that images with lots of adjacent light and dark areas, such as sun shining on leaves, will get annoying white hot spots when sharpened. If your program has a sharpen edges feature, this may be a more attractive option for such images.
If you have have a recent version of Photoshop, there's a very simple and effective method you can use. First, pick sharpen from the filter menu. This may make your image look oversharpened at first. Now pick fade from the edit menu and move the slider until you're happy with the appearance of your image.
Here's a partial list of tools and tips:I don't know. I've read many discussions of this and tried many tools for it without finding anything that feels like B&W to me. My current favorite approach is DigiDaan's channel mixer method. Here are some other approaches:
These are called hot pixels. Most sensors produce them. Your camera may have some noise reduction features designed to minimize this effect, so you should first check your manual to make sure that this feature is enabled if it is available.
If you're stuck with hot pixels, you have several options. You can use a technique called dark frame subtraction. This technique, along with an in-depth explanation of the hot-pixel phenomenon can be found here in the learn section of dpreview.
There are also some program and plug-ins available for dealing with this specific issue:
Tall buildings appear to be leaning backwards because you tilted the camera up when you took the picture. Here are some tutorials and tools for fixing this:
There are many methods for dealing with noise in high ISO images. My favorite is Jes's color grain reducer. I've even done a little tutorial on cleaning up high ISO images, which uses Jes's photoshop action. I like Jes's action best because it cleans up color noise without corrupting the image. There are plenty of other approaches. In my opinion, these are inferior, but you might want to give them a try:
Some comments about noise reduction: Many people are initially infatuated with noise reduction techniques until they realize that removing noise almost always implies removing some detail from the image. Images processed with these methods will often get an unnaturally smooth look to them, with long areas of flat texture. Getting good results will require a light hand and lot of patience no matter which program you're using. My one exception to this rule is Jes's noise filter, mentioned above. I've never seen it remove detail. This conservative approach will definitely leave some noise behind.
There is a new batch of computationally intensive noise reduction techniques that have become popular in recent years. In general, these do a better job of walking the fine line between noise reduction and detail destruction:
Try Virtual Dub.
Most photo editing programs come with a few cool effects built in. You can achieve many more by mastering the options available to you in your program and combining them in creative ways. There are still other options available to you in the of standalone programs and plug-ins:
The first thing that you need to understand about digital pictures is that they don't have an inherent DPI rating. That's right, the resolution of digital images is not measured in DPI. Digital images are collections of pixels. The DPI of an image depends entirely on how you decide to display it or print it.
But if digital images don't have any inherent DPI, why does my image editor display DPI for images? Your image editor keeps track of two things, your image and the size at it which it expects you will print the image. These are two completely separate things, so your image editor might start off thinking you want to print your image at some goofy size (usually the result of assuming you want to print at 72 DPI, which is the presumed resolution of most monitors) but this doesn't matter. You can change the size at which your program thinks you want to print the image, thus changing the DPI, without altering your data at all. Your image editing software will have a specific way of doing this. In Photoshop family products, you pick "image size" and make sure that the "resample image box" is not checked. This means that Photoshop won't alter your image; it will merely alter its own internal idea of how large of a print you will be making from your image. You can make this change by either changing the DPI or by changing one of the dimensions of your image. All of these numbers are linked together, so you need only change one. (Shrinking the print size of the image increases the DPI because you're squeezing the same number of pixels into less physical space.)
If you want to change the number of pixels in the image, then you should resample the image in some way. In Photoshop derivatives, this means checking the resample box. Typically you will do this when you want to shrink an image for display on the screen. However, there are times when you may want to resample an image for printing. This would be necessary when the DPI become unacceptably low (below 150) at the output size you have selected (more below). When you are resizing an image with resampling, you can enter the new resolution of the image in pixels, or adjust the DPI. The program will assume that you wish to keep the output dimensions constant at this point. However, if you change the print size, the program will scale the pixels and DPI accordingly.
When you are change the number of pixels in an image, be sure to use a sophisticated resampling method such as bicubic resampling. Other methods may be faster, but they can create jagged looking images.
If you want to read more, or check out some sophisticated methods of upsampling to print very large images:
This information is stored in inside of your files in something called an EXIF header. See below...
If you are running Windows XP, you can view this information by examining the properties of the file in question - although this will not display all of the information stored in the EXIF header.
If you are running a different OS or want to see more of the information in the EXIF header, there are other options. My favorite is PixVue (Free). Some others:
You can also view EXIF information from inside of many image viewing programs, such as irfanview.
My favorite is irfanview by far, because it's fast, flexible and free. Some others:
Here's a great tip on getting irfanview slideshows to autorun when a CD is inserted. (Additional tip from Ulysses: You can use irfanview to genereate the slideshow list, so you don't have to enter the filenames manually.) Note: I have tried it yet, but recent versions of irfanview have, apparently, automated some of this.
I don't have many but here goes:
Check out gphoto, and don't forget about the GIMP.
In the context of digital cameras histograms refer to a histogram representation of the intensity levels in an image. See The Imaging Resource for a more detailed discussion.
There are many techniques for doing this, some of which I hope to cover in more detail at a later date. For now, keep in mind that most intermediate to advanced image editing programs have some kind of "auto levels" or "level correct" feature built in. These will often do a decent job of guessing what the correct color and contrast should be. Some programs, shuch as Photoshop Elements, have a specific tool that allows you to do after-the-fact white balance setting by click on neutral objects in the image. For more discussion and software tools for color balance adjustment:
These are optical effects caused by your lens. Reducing these effects typically requires producing a larger, heavier lens with more elements, so what you are seeing is a tradeoff of cost and weight against image quality.
There are web sites and software tools that will help you correct for this:
You have many options for fixing red-eye in software. Many image editing programs come with features designed to facilitate this, so check your manual. PhotoDeluxe and Photoshop Elements both have built-in features for this. Ironically, full Photoshop (this Swiss Army chain saw) does not have these features.
The basic skills for red-eye removal are quite simple and can be done in a variety of ways (without using any special red-eye features) in most moderately sophisticated programs. Once you realize how easy it is, you may prefer to do it yourself because you'll have more control. Here's what you need to do (one eye at a time):
If you master these simple steps, you can take out the red-eye from most shots in about a minute. Here are some more references:
In Windows ME, 2000 or XP select view and then thumbnails.
Many people incorrectly believe that this cannot be done in Windows 98. It just requires an extra step. (If you have a really old version of Windows 98, you might need to download some of Microsoft's updates first.) Open the properties dialog for the folder for which you wish to display thumbnails (right click, then select properties, or highlight the folder, then do file->properties). Now check enable thumbnail view, and proceed as above for newer versions of Windows. Note that you may need to close and restart Explorer, or even restart Windows, for this to work the first time.
A typical image editor will decompress and recompress a JPEG file when you save it, resulting in a loss of image quality. You can avoid this if you use special software that can do a very limited set of operations that don't involve recompressing, i.e., they just rearrange the data already in the file. You are typically limited to rotations at multiples of 90 degrees and some cropping actions:
There are many others than I haven't listed. (See here for more.) Of course, I haven't tried all of these and some may be better than others. Some advice: Read the instructions carefully to make sure that you're actually doing what you think you're doing. In some of these programs, you will need to follow special steps to ensure a lossless operation. Finally, remember that here "lossless" means that no further degradation will occur. Some image quality was lost on the first save to jpeg and nothing can ever recover this.
Resources abound for this including (gasp!) the manual. Here are a few:
If you don't know what I'm talking about, see: What are those red and green color fringes in my images?
You can partially correct for chromatic aberration using software tools. If you are shooting in RAW, then there's a very nice interface to this through the Photoshop CS RAW converter, and now through CS2 even without the RAW converter.
If you aren't using a recent version of Photoshop then it can be done using using Picture Window Pro, as described by Norman Koren. Another alternative is to use panorama tools. See tutorial 1, or tutorial 2.
I started by indicating that one could only partially correct for CA. Why don't these techniques fully correct the problem? There are two reasons:
See also: How do I avoid chromatic aberration (CA)?
If you don't know what I'm talking about, see: What is that purple fringe around high contrast areas in my photos?
There is no known technique for correcting for purple fringe. However, you can hide it. The basic idea is to selectively desaturate the regions and color ranges involved. This will have the effect of replacing the purple fringe with a gray fringe, which is often far less objectionable. If you're facile with image editing software, you can figure this out for yourself. Otherwise, you might benefit from Shay's color fringe reducer.
See also: How do I avoid purple fringing?
Some cameras, e.g. some Canon models, come with software that lets you snap images and adjust settings through a software user interface on you computer. For other models you may need to acquire additional software, sometimes from a third party. Newer cameras are increasingly using a standard called PTP, which should allow the camera to be controlled through a standard protocol. As with many standards, however, not everything is entirely standardized.
Here are some third party applications for controlling your camera:
Color is the perception of the power spectrum that is striking our retinas. Cells called cones are responsible for our perception of color. There are three distinct types of cones and each type covers a different region of the spectrum. The cones are typically labeled as red, green, and blue, which gives the incorrect impression that each responds to a distinct frequency. In fact, there is significant overlap between them, especially in the case of red and green.
Since the stimulation level of these three different types of cone cells determines our perception of color, we can also talk about color mathematically as a point in a 3-dimensional space.
A power spectrum is the distribution of light energy at different wavelengths. This can be viewed as a graph where the vertical axis is energy and the horizontal axis is wavelength.
Not exactly. We have 3 types of cone cells that contribute to our perception of color, so all color can be described in terms of the relative stimulation of these cells. However, the physical phenomena that cause our percpetion of color are not necessarily composed of three primary colors.
How do we reconcile these two thoughts? Let's consider the primary colors green and red. We can talk about pure green light, which is typically around 510 nm, and pure red light, which is typically around 650 nm. If we mix these together in approximately equal proportions, we will get th