Sunday, July 24, 2011

Some basic photography tips.

Cameras do lie. They lie a lot. They like to lie. One of their favorite ways to lie is by having very shallow dynamic range compared to the human eye. Dynamic range in this case means the ability to handle extremes of light and darkness. HDR ( high dynamic range ) photography attempts to overcome this shallow range by using multiple frames of the same image, shot at different exposure values, and then recombining those frames to compress said range into a single image. It's still a lie, but it can look pretty cool, or it can look pretty bizarre and ugly.

In the old days before HDR people like Ansel Adams used some pretty tricky techniques in the field and the darkroom to get very similar, ( but typically more artful ) results to HDR photography, including the combining of multiple frames shot at different exposures. "unsharp mask" was also created in the darkroom, "dodging and burning" and so on. A lot of the stuff that you see today in photoshop was originally discovered or invented, or at least studied by photographers who died before we were born. We owe them some respect if we're going to call ourselves "photographers."

The art of photography is the most important thing. It's a human art. Technique and technical matters come second. That being said, if you aren't going to learn anything about how your tools work, why not? You learned to read, you learned math, so what's the problem?

Cameras have parts similar to the eye and parts not so similar.
The general sensitivity to light is called "ISO" or formerly as film speed "ASA". Think of it as how well you can see in the dark, or how much bright light is more than you can stand. High ISO like 1600 means very sensitive to light. Low ISO like 100 means not so sensitive, but can handle bright light.

"Aperture" is very like the pupil of your eye, it also helps to control how much light enters the camera to be utilized. A smaller aperture lessens the transmission of light. Larger apertures let more light in. It's that simple; except that small apertures also increase "depth of field" which means more of an image will be in focus from front to back. A very small aperture, such as a "pinhole camera" has such great depth of field that it doesn't even need a glass lens, just a pinhole. You don't have to focus a pinhole camera, everything is in focus. Small apertures can also help a crappy lens look a bit sharper.

"Shutter speed" is the last aspect of controlling the quantity of light entering the camera. This is also similar to your eye, sort of. Did you know that 24 frames per second was discovered to be "persistance of vision?" This is the rate at which your eye can basically stop motion. It's pretty slow. This is one area where cameras tend to beat the human eye on two points: a very long (slow) shutter speed can allow a camera to see in the dark. Your eye can't do that. You can stare at the same night scene as long as you want and it won't get any brighter. Conversely a fast shutter speed, say 1/4000th of a second can freeze motion like your eye can't. They call it "shutter speed" because it's very like opening and closing a shutter. In the old, old days some cameras had no shutter-- you simply removed the lense cap, and then put it back on again. You can still do this, especially with a pinhole camera. It's fun. Shutter speed generally does not affect image quality such as depth of field, like aperture does, but this confuses people because a slow shutter speed can cause images to come out blurry if anything moves or if you shake the camera. That's why so many pictures shot in low light tend to come out blurry. Moving on. . .

You can buy a camera and put it on "auto" and take a lot of pictures. Now that we have digital cameras, you can shoot thousands of pictures and it costs you nothing. Sooner or later you will get lucky and get some nice shots. You won't know how you did it. You won't be able to do it again without taking a lot more pictures until you get lucky again. You will miss a lot of great shots because your camera on auto will make some dumb decisions which ruin the shot. One of the dumbest decisions a camera can make is choosing from about 2 dozen autofocus points all over the frame. Cameras can make many many many dumb decisions. Wouldn't you rather make your own? At least you can be proud of them after the fact.

Oh yeah, "f-stops" are aperture measurements. A big number is a small aperture. Like F22, it's small but not a pinhole. Memorize that. Big number is a small aperture, lets in less light, but has greater depth of field, also called "depth of focus" but don't say that, because other photographers will peg you as a novice. A big aperture is a small number, like f2.8, or f1.4 or f1.2. It lets in a lot of light, but the depth of field will be shallow. With a big aperture like f1.2 a portrait photographer can have your eyes and lips in focus, the tip of your nose soft, and the background all nice creamy blur. The out of focus blur is called "bokeh". The quality of this blur is like fine wine to a photographer. Don't ask me why, we're funny that way.

If you can remember that big numbers in f stops like f22 are small apertures which let in little light, and that big numbers in shutter speeds like 1/4000th of a second are fast shutters which also let in little light, it will be helpful to you. ISO is the opposite. Big numbers means more light sensitivity. Somewhere a photographer invented this system just to confuse the hell out of you.

I brought up f1.2 in case you wondered where they get those strange numbers. If you had a lens whose maximum aperture is f1, that means that the ratio of the focal length of the lens relative to the internal diameter of the lens is a one to one ratio. Not exactly, though, I've simplified it for you because it involves the focal length of the lens relative to the film plane, but close enough. An f1 lens is a FAT lens ( literally and figuratively ). If you have one, send it to me.

So, those are most of the basics of how a camera controls the quantity of light used to produce an image, and the why of it: a camera with with a much much wider "dynamic range" would not need any of these controls but even our eyes have limits like pupils ( aperture ) persistence of vision (shutter speed) or ultimately the sensitivity of the "rods and cones" and the optic nerve ( ISO or ASA referred to as film speed )

If any of this confuses you just remember that a simple camera is just a box with a hole in it, and every other camera is just a variation on that theme.

Next time maybe, "white balance" AKA "color temperature" expressed in "Kelvins" if anybody wants to know.

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