Frequently Asked Photography Questions 

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General Photography
Lenses and optics
Flash
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Software and editing
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Digital Photography

General Photography
How do I take good portraits?
What procedure will let me use wide apertures even in conditions of bright light?
How do I reduce glare off surfaces?
How can I get more dramatic looking skies in my shots?
Why is it so complicated to get the exposure right on my pictures?
How do I set the exposure on my camera?
When do I use aperture priority (AV) mode and why?
When do I use shutter priority (TV) mode and why?
What is the minimum shutter speed I should use to avoid blurry photos due to camera shake?
Are smaller cameras more susceptible to image blur from camera movement?
What's the difference between my camera's different metering modes and how do I know which to use?
What is ev compensation?
Why do so many of my shots using the timer come out blurry?
What conditions warrant the use of high ISO?

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Lenses and Optics
What is diffraction and how does it affect my photos?
The corners of my images are darker than the center at the telephoto end of my zoom's range. Is my lens defective? (vignetting)
What are those red and green color fringes in my images?

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Flash
What's the advantage of getting an external flash?
What causes red-eye and how do I minimize it?
Why does my flash not seem to work properly on macro shots?
Is there a way to use a ring flash with my digital camera?
What is a slave flash?
Why do my flash shots have a red cast?
Why do my flash shots have motion blur?
Why do I get such long exposure times when using the flash in aperture priority mode?
Why do my flash shots have a lot of noise?

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How do I take good portraits?
Use longer focal lengths instead of shorter (telephoto instead of wide angle). This will make your subject's face more natural and less bulbous.Use a wide aperture for shallow depth of field. This will focus attention on your subject and not your background. Avoid distracting backgrounds.Try to achieve even illumination by exploiting natural light. If you can't use natural light, then use studio lights and/or multiple flashes and/or a bounce flash. Avoid taking pictures where part of your subject's face is in shadow unless you really know what you're doing. Avoid using a single flash pointing directly at the subject. This will create harsh shadows on either the subject of the area behind the subject.

There are several sites that offer tips on portrait photography:
Portrait Photography Tips
Photo.net's tips

What procedure will let me use wide apertures even in conditions of bright light?
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.

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How do I reduce glare?
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.

How can I get more dramatic looking skies in my shots?
Try a polarizing filter, which can also be used to reduce glare.

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Why is it so complicated to get the exposure right on my pictures? (Why doesn't the camera just capture what my eye sees?)
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. 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.

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How do I set the exposure on my camera?
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.

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When do I use aperture priority (AV) mode and why?
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:

Selecting a small aperture to maximize depth of field.
Selecting a large aperture to minimize depth of field.
Selecting a large aperture to maximize shutter speed in low-light or fast-action situations.
Choosing an aperture that maximizes the sharpness of your lens. (Every lens has an aperture at which it is sharpest.)

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When do I use shutter priority (TV) mode and why?
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:

Selecting the slowest tolerable shutter speed to minimize aperture (maximizing depth of field).Selecting a high shutter speed to freeze action.

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What is the minimum shutter speed I should use to avoid blurry photos due to camera shake?
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.

Are smaller cameras more susceptible to image blur from camera movement?
Depending upon weight, balance and ergonomics, it may be harder for you to hold a small camera steady.

Some people mistakenly believe that cameras with a smaller capture medium (sensor or film) or more susceptible to blur than cameras with a large capture medium given the same field of view just because the capture medium is smaller. This often manifests itself through the misconception that compact digital cameras will produce more blur for a given amount of camera shake than traditional SLRs. This can be debunked with a simple thought experiment: Consider two cameras, C1 and C2, with the same field of view, but suppose C1 has a larger sensor. Place C1 at some starting point and move it along a trajectory through space. Now do the same thing with C2. Since C1 and C2 have the same field of view, they must see the same thing at every point along the trajectory. If the shutter is open while the cameras are moved, then the resulting blur must be identical as well, since both cameras saw exactly the same thing during the exposure.

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What's the difference between my camera's different metering modes and how do I know which to use?
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.

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What is ev compensation?
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.

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Why do so many of my shots using the timer come out blurry?
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.

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What conditions warrant the use of high ISO?
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: Indoor, handheld shooting in available light (no flash).Shooting fast action that requires a very high shutter speed. Handheld shooting with a very large focal length.Another reason for increasing ISO is to extend flash range. The higher sensitivity will allow you to a less powerful flash for longer distances.

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What is diffraction and how does it affect my photos?
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.

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The corners of my images are darker than the center at the telephoto end of my zoom's range. Is my lens defective? (vignetting)
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.

What are those red and green color fringes in my images?
You are most likely seeing classic chromatic aberration (CA) which 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.

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My camera already has a flash built in. What's the advantage of getting an external flash? 
External flashes are more powerful, so you can illuminate objects further away. An external flash will position the flash further from the lens, which will reduce red-eye. Most external flashes have pivoting heads, which permit you to bounce the flash off the ceiling, further reducing the chance of red-eye and giving the scene a gentler, more natural illumination.

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What causes red-eye and how do I minimize it?
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:
1. Minimize the subject's pupil size, thus reducing the amount of light that reaches the retina to be reflected back. The so-called red-eye reduction modes in many flashes and cameras today try to do precisely this by hitting the subject with a "pre-flash" of bright light designed to make the pupils constrict. The effectiveness of these methods varies quite a bit. The method of twinkling the flash rapidly for a second or two seems to be most effective - if it doesn't cause seizures in your subjects. Some cameras try to reduce pupil size by simply blinking a small bright light. This does not appear to be as effective as the twinkling flash method. Another less obvious tip is to avoid situations where pupils are likely to be dilated: Try to have people look into light and avoid taking pictures of drunk or otherwise impaired people.

2. Increase the angle from which the flash light is hitting the subject.  If your flash is very close to your lens, the full intensity of the flash light will bounce off the subject's retina and come straight back into the lens. You can increase the angle by moving closer to the subject or using an external flash, which moves the light source further from your lens. (Note that an unfortunate consequence of all of this is that those nifty, tiny little pocket cameras are the worst performers when it comes to red-eye. Their flashes have to be close to the lens because the camera is so small and they typically don't accept external flashes.)

3.Diffuse the light hitting the subject. The typical way to do this is to use an external bounce flash and bounce the flash light off the ceiling. This has the effect of illuminating the entire scene, rather than hitting the subject with a burst of intense light. It tends to reduce harsh shadows too. If you don't have a bounce flash, you can try attaching a diffuser to your existing flash or coming up with an ad hoc diffuser. Be careful with ad hoc diffusers: If they reflect light back into the flash, they can cause overheating and damage your flash.

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How do flashes work?
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.

Why does my flash not seem to work properly on macro shots?
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.

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Is there a way to use a ring flash with my digital camera?
Probably, but depending upon your camera's support for standard external flashes, it may require some persistence and some workarounds:

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What is a slave flash?
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. 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.

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Why do my flash shots have a red cast?
If you are using your camera in auto mode, it may be choosing a shutter speed that is too low. 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.

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I thought that the flash was supposed to freeze action. Why do my flash shots have motion blur?
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.

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Why do I get such long exposure times when using the flash in aperture priority mode?
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: In manual mode, some cameras (e.g. Canon SLRs) will increase flash power to provide light needed for proper exposure, up to the limits of the power of your flash. Some cameras may have options that allow you to override the assumption of fill flash in aperture priority. Check your manual.

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Why do my flash shots have a lot of noise?
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.

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