In my instruction I get asked a lot about how the five most fundamentally important settings of the camera work together to achieve the effects you desire. It can be hard to penetrate the curtain of photographic jargon, some of which can seem counterintuitive, so I decided to take a minute to explain all of this stuff at a very high level. If you have specific questions of your own, please leave a comment below and I promise that I will answer them.
The only five settings that you need to know are:
- Shooting mode
- Aperture (or f-stop)
- Shutter speed
- ISO sensitivity
- Exposure value (EV)
After the jump I will explain in detail.
Each of these settings affects the others. It's like a five-way see-saw where changing one setting will require that you change another to compensate for it. So why change the settings at all? Because each setting has a different aesthetic effect on your image.
The shooting mode refers to Av, Tv, P, M on Canon cameras, or A, S, P, M on Nikon cameras. They mean:
- Av/A = You select the aperture, the camera selects the shutter speed.
- Tv/S = You select the shutter speed, the camera selects the aperture.
- P = The camera selects both (bad camera!)
- M = You select both (you're a pro!)
The reason you might want to select your own aperture is to control the depth of field, which is how blurry things will get (or how sharp they will remain) the farther they are from your focus point.
You may want to change your shutter speed, also, in order to freeze motion or to get the effect of a long exposure.
By altering your ISO sensitivity, you can get longer or shorter shutter speeds and larger or smaller apertures, but the higher your ISO, the more noise you will see in the image, while the lower the ISO, the less noise you will see.
The exposure value (EV) is only applicable if you're in Av/A, Tv/S, or P modes, and allows you to override the camera's light meter to make it overexpose or underexpose the shot by a certain amount. I'll talk about this feature last.
Learn to talk the talk
You will hear people talk about lenses or settings being “faster” or “slower.” You would think that they're talking about shutter speed (because it's a speed, right?) but you'd be wrong. We say “faster” when we're referring to a larger aperture, which, contrary to common sense, means a smaller number. Okay, let me back up for a second.
- Larger aperture = smaller number = “faster”
- Smaller aperture = larger number = “slower”
Get it? We say a larger aperture is faster because it allows you to use a faster shutter speed. A larger aperture (smaller number, right?) means more light. More light means you don't have to expose the sensor for as long, so your shutter speed is faster.
A Balancing Act
As I mentioned earlier, changing your camera settings, put simply, is like a balancing act. Once you understand the concept of “stops” and how each setting affects light, you're on a roll.
What's a stop?
A “stop” is a relative measurement of light, meaning that “one stop” of light is not an absolute amount. Rather, plus one stop means twice as much light, and minus one stop means half as much light. When you work with your camera settings, be aware that modern cameras typically measure their settings in 1/3 stops rather than full stops.
The faster the shutter speed, the less light will make it to the sensor in total. The slower the shutter speed (i.e. the longer it remains open), the more light will make it in.
For each full stop longer that you leave the shutter open, twice as much light will enter the camera.
The aperture, as you probably know, is the opening through which light passes on its journey through the lens. What is confusing about aperture is that it's measured by the “f-stop,” which is a number that gets smaller as the aperture gets bigger. As long as you can remember this odd, inverse relationship, you're fine.
For each full stop that the aperture number increases, half as much light will be let into the camera. For each full stop that the aperture number decreases, twice as much light will be let into the camera.
ISO is on a different scale, but it's much easier to understand. As the ISO number doubles, so does the light, thus ISO 200 is twice as sensitive to light as ISO 100. That difference is… Yes, one full stop. Cameras these days frequently let the photographer select among half-stop or third-stop ISO increments as well, but it's pretty easy to tell that the full stops are 50, 100, 200, 400, 800, etc., because the numbers double.
This is a tough subject. Metering is the process of evaluating how much light is in a scene, something that we generally let our cameras do because they're much more accurate than our eyes. Nevertheless, sometimes what you want out of a scene, as an artist, is different from what the camera “sees.” There are a couple different common metering “modes,” which have different names based on your type of camera, but in general they are:
- Evaluative (or matrix)
- Center-weighted average
These modes have to do with what portion or portions of the scene the camera's meter will take into account in its calculations. Spot means that it will only look at the center point of what you see in the viewfinder, usually 3% or so of the middle of the scene.
Partial is a somewhat larger measuring area, around 10% or so (check your camera's manual to find out the specifics). Center-weighted gives more measurement priority to the middle area of the scene, but also averages it against the rest.
Evaluative or matrix metering is sort of like black magic; the camera basically meters for the subject and then also figures in adjustments based on the surroundings. It might use the focus point or other variables to figure out what the subject is. Like I said, black magic. Usually I keep my camera in evaluative mode because it deals with diverse circumstances very well.
In very general terms, the meter wants to look at some amount of reflected light and determine the settings necessary to make that area show up in your photograph as “middle gray,” or 18% gray. If you were using spot metering and you pointed that center spot right on a bright white piece of paper and took a picture, it should look gray. Why does it do this? Because when you take the average of a large area and make that whole area average out to 18% gray, it's usually the exposure you want. Usually.
When it's not the exposure you want, that's where exposure value (EV) comes in.
EV compensation is only used in the auto-metering shooting modes, like Av/A, Tv/S, and P. If you are in manual (M) mode, you are selecting both shutter and aperture values, so the camera's meter is informing you of its readings but isn't changing any settings for you. Thus, if you want the scene to be exposed lighter or darker, it's up to you to change either the shutter speed or aperture appropriately. Anyway, here's an example.
If you are shooting a snowy, winter scene using evaluative (matrix) metering mode, your camera is going to look at its entire view (which is predominately white) and expose it to look gray. Obviously you want the snow to look white, so you “fake out” the meter by setting your EV to, say, +1 stop. This causes the camera to change its settings to expose the scene one stop brighter than it normally would, which should make the snow look white.
You might also need to use EV if the camera overexposes a portion of the scene that you didn't want it to. To fix that, set your EV to a negative number (“stop it down”).
Why have I told you all of this? How does this information possibly make you a better photographer? I don't know, maybe it doesn't. My point in telling you all of this is that you need to closely control your aperture and shutter values in order to achieve the aesthetic effect that you want, but when you change any one of the values, you probably have to compensate by changing another value. By understanding how these five core settings interact, you can then focus your attention on composition, form, color, contrast, line, and the other artistic characteristics of your work.
If you want to learn more about how all of these things work, and you want to take some pretty pictures with me at the same time, sign up for one of my workshops. I've got a workshop coming up in Boston, and then another in Cape Cod!