Automatic Cameras

Automatic cameras are highly trustworthy and can produce consistently good results, as long as you understand them. The problem is that automatic cameras are easily fooled. If there is also a fool trying to use it, results become highly variable. The cameras have little intelligence, relying for that upon the user. Here are some "Gotchas!" and how to avoid them.

Auto-exposure


The camera seeks an average. Photograph a black card, a middle grey card and a white card, and you end up with three grey cards. It increases the exposure with the black card, in order to achieve the average and decrease the exposure with the white. Only the grey gets correct exposure.

I recall a message in a forum that clearly reflected this. The writer was trying to photograph some pieces of jewelry on a white background, but got grey instead of white.

He tried a more intense light and still got grey. Finally he tried shooting it in full sunlight and once again the same tone of grey, so he decided his camera must be defective.

It was simply acting as any camera would under the circumstances. Every time he increased the level of light, the camera compensated by shortening the exposure. The solution was to either use the camera's exposure compensation adding 2EV or by adjusting the histogram by using levels in an image processing program.

A pair of mid-tone pewter objects and the effect of the background. The lighting was consistent across all three, and the exposure was read from the backdrop near the top of the tankard handle.
When photographing anything, it is important that the subject's reflected luminance matches that of the background. A black Labrador retriever frolicking in a field of snow will show almost NO detail at all, while the snow will have a great deal of detail. Photographed against dark grass or deep shadows, the detail will be excellent.

The opposite is also true, a brilliantly lit stage performer against a black backdrop will be burned out and lacking detail, while the background will be nearing a medium grey. With slides or digital photography, this can be a disaster. While shadow detail can often be extracted through careful processing when the image is under exposed, when it is overexposed, burned out highlights have nothing to recover.

Willie Nelson was brilliantly lighted against empty blackness in Dallas' Reunion arena. Since I was shooting for his record company, I was close enough to do a very accurate spot-meter reading from his cheek. Had I shot a wider shot with full automatic, all detail would have been totally washed out. In the case of the raven, I risked moving to an angle where there was a dark forest in deep shadow on the mountain side behind it. This boosted the overall exposure to the point where great detail came out in the raven's plumage.
Other potential problems are shooting when there are actual light sources in the picture. A table lamp will force the camera to compensate for its much greater brightness than the rest of the scene, and so underexpose the subject.

Photographing the subject indoors with an outside window behind will cause the camera to expose for outdoor light. Obviously, the solution would be to use fill-flash, to balance the subject, right? Not always. Windows are reflective and if the reflection is seen by the camera, the flash shuts down much too soon. Moving to an angle where the reflection is not seen, would fix it.

Using exposure compensation can get you close in most cases. If not, only full manual exposure is the answer - if your camera provides it.

To compensate, you must be actually aware of the potential problem. If you trust the camera to do your thinking, you lose the pictures. Digital cameras have the advantage of being able to let you review each shot immediately after it is taken. When in a situation where any chance exists for bad exposure, do test shots and continue making adjustments until your exposures are right. This means being constantly aware of the environment in which you are shooting.

Auto-focus

Auto-focus relies on contrasting edges to find the focus and lock-on. Given a blank wall, the camera becomes totally confused. In most normal scenes, trees, buildings and even clothing will have contrasting edges. Of course, the camera can not read your mind and determine which lines are on your subject. When shooting a low contrast subject against a very busy background, the camera is most likely to choose the background, throwing the subject out of focus.

Many cameras will allow one to point at a contrasty object at the same distance as the subject, press the shutter half way, and focus will be locked. Turn back, frame the subject then press the shutter all the way. The only other alternative in this case is to use manual focus.

However, many compact digital cameras have such small sensors and short focal length lenses, that accuracy in focus is of minimal importance, specially when using wide angles.

Using the equivalent of a 19mm lens, stopped down to f-8.0, everything from about an inch in front of the camera to the horizon is in focus.

Camera Motion As A Cause Of Blur

Camera makers are competing to have the longest ratio zooms currently. Few professional photographers ever use a 300mm or longer telephoto. Those who do tend to be specialists with the great skills needed to deal with the problems they present. Now Canon, Sony and Panasonic have lenses that goes to the equivalent of 432mm, Samsung and Kodak to 420mm, Fuji and Nikon to 380mm and there may be more.

At the extreme, these lenses present a whole banquet of problems, but the main one is often attributed to focus. However, it is not focus, it is camera movement. The Nikon CP5700 was the first of the very long ratio zooms to hit the market, and it immediately gained a bum rap of not being able to focus. I questioned this and many people sent me images to prove it. Every single image was a profound example of camera movement.

Film shooters have long had a rule of thumb based upon the focal lengths used in 35mm photography. Minimum shutter speed for hand-holding, must be at least 1/(focal length). Thus if you are shooting with the equivalent of a 400mm lens, the slowest shutter speed should be no lower than 1/400th of a second. Some of the blurred images sent to me were well under 1/30th of a second and of course were terrible.

Many in the current generation have image stabilization, which extends the range down to somewhat slower shutter speeds, but there always is a limit. Photographers need to always be aware of their shutter speeds and use aperture and sensitivity to keep it in a usable range.

By increasing the ISO setting, there is an increase in noise in most cameras. However, given a tack-sharp image with considerably graininess compared to a satiny image that is burred beyond recognition, I will take the grain anytime.

When the camera is set upon Program mode, a programmer in Tokyo or Seoul is choosing the settings for what you are shooting. In low light situations, choosing Aperture Priority and shooting with the aperture wide open, you will always have the highest shutter speed that your ISO setting and circumstances will allow.

Shutter priority can be really treacherous with compact cameras. Few have lenses faster than f-2.8 and few have apertures that stop down below f-8.0. (The smaller the number, the wider the aperture.) With the lens set between f-2.8 and f-8.0, you only have a 1.5EV - a stop and a half - margin before either over or under exposure. Once you begin to zoom toward telephoto, the margin drops drastically. To use it, you must CONSTANTLY monitor to make sure you are within these margins. With its limitations, I find it useless.

Auto white balance

Some early digital cameras had such an effective white balance, that the most glorious sunset had every bit of the colour drained out of it. Now most cameras are much more conservatively equipped. The effects of auto white balance are almost imperceptible when shooting in light provided by household bulbs, streetlights and a lot of fluorescent lights. Now, sunsets can actually be photographed in full colour.

This presents problems with the other light sources. Most cameras that go beyond simple point-and-shoots have settings for at least some of these sources and many have a manual white balance, which is best. Point the camera at a white piece of paper, or other than the sun, the light source itself, and tell the camera to do the balance. Of course, you must do this again every time the light source changes, but it will produce very good results.

Higher-end cameras have RAW format. In this case, the camera's processing is completely bypassed, and the raw output of the sensor is saved in a data file. A piece of software replaces the camera's firmware and embedded computer. In difficult lighting situations, this can be the best solution by far. It allows the user to make all the decisions on exposure, contrast and colour balance. It may also allow one to set the precise amount of sharpening wanted, scale the image larger or smaller and even correct aberrations of the lens or sensor - before opening the image in an image processing program! While RAW does offer a lot of advantages, it also requires a good bit of understanding of how photography works and image processing skill on the part of the user.

Using RAW along with layers and layer masks, images shot under mixed light sources can have different colour balances for each area, and be merged together into a single well balanced image. If shot for maximum highlight detail, again layers and layer masks can be used to protect the highlight detail while gradually bring up the shadow detail under great control.

RAW format makes dealing with extreme contrast ranges and difficult mixed light colour balancing possible, using layers and layer masks. Even though these two were sitting side by side, due to the predominantly neon light, each required quite a different exposure and colour balance. RAW also provided considerable compensation for the extreme contrast range of scene.

Automatic cameras are great if the user thoroughly understands how they make their decisions. Shooting with manual cameras, you had to take the light reading with a handheld light meter and transfer the settings to the camera, so you were always aware of your situation.

Under a certain range of circumstances, automatic cameras do work well, allowing the photographer to apply less attention to camera operation and more to content creation. Outside of that range, they can bite you. One must always be aware of what is in the view you are shooting, and all the hazards that can ruin your image. Automatic cameras only work well when the user takes full control of them, using settings appropriate to the venue, shooting test shots and making adjustments, and always being aware of what the camera is trying to do on its own.

©2006 Larry N.Bolch