This is a hastily-added chapter and needs more diagrams/charts rather than just words -Dan
By now, I hope you’ve gotten some practice with putting your camera in Program mode and adjusting the exposure on your own.
And you should be comfortable with making the adjustments without much thinking.
Because soon you’ll have multitask adjustments for exposure and for at least one other setting. This is in addition to watching out for interesting things to photograph.
Some of this boils down to muscle memory; the good (or bad) design of your camera’s controls can be a factor.
But thankfully, successfully managing your camera’s settings on the fly depends more on wisdom and basic problem solving skills than it does pure muscle memory.
When I overexpose (or underexpose), how is the camera letting in more (or less) light?
In Program mode, you’re controlling the amount of light used for the photo. But your camera is taking care of the details, balancing the shutter speed, aperture, and ISO to get you the desired exposure.
In the graphic below, the exposure value, highlighted in green, goes from 0.0 EV to 1.0 EV:
Notice how the shutter speed, highlighted in red, is halved in order to let double the light in, while the ISO and aperture remain the same.
How does the camera know which of those factors is most important?
Good question. It doesn’t.
By default, it’ll make a reasonable guess that will work most of the time, just as it did with exposure.
But it won’t know which of those three factors is critical for the photo that you want.
And each of those factors, if pushed too far, can have very undesired effects.
What’s the worst that can happen?
Generally, the worst and least fixable issue is motion blur. This happens when the camera slows the shutter speed to a rate such that the movement in your hands or by your subject results in a blurry photo.
What are the negative effects from aperture and ISO?
If your camera pushes ISO too far, it will result in ugly, pixelated noise that ruins fine details. For photographers who intend to make poster and billboard-sized prints, this becomes a particular concern.
When the camera pushes aperture to its maximum, it results in a shallow depth of field. This reduces how much of the scene will be in focus, depending where your actual focal point is.
For example, with an extremely shallow DOF, if your camera is focused on the model’s nose, his eyes will be out of focus.
So now I’m expected to keep track of exposure and three other factors?
Not exactly. You can adjust each setting yourself when your camera is in full Manual mode. But I rarely do this myself, as that is too much multitasking unless I’m staging a photo in a studio.
In more informal settings, you’ll prioritize either shutter speed or aperture. There’s not really an ISO-priority mode, but you can set that to Auto or to a specific number.
How difficult is it to manage exposure level and another setting?
It takes some practice and you’ll likely screw up many times, even as you get used to the motions of twiddling your camera’s controls while judging a scene.
But you’ll eventually figure out the general pattern. Before you walk into a situation, you’ll have your settings in place because you’ll have an idea of the kind of light to expect and exactly what you intend to capture in a given scene.
For example, this is what I do when I walk around at night:
I know beforehand that I won’t be using my flash. So I’ll be looking for objects that are illuminated – or silhouetted against – artificial light sources.
- I set my exposure value to -1. As I explained in the underexposing, I like emphasizing the available light sources and keeping the rest of the scene in shadows.
- I set my camera to shutter priority mode.
- I set the shutter speed value to 1/40th of a second. This is because I know I can control my body’s movements enough to prevent the kind of camera shake that ruins a photo.
- I set the ISO to 1600 because my camera’s sensor can produce a clean enough, printable photo at that level.
This leaves the camera to handle the aperture. Which is fine with me, because there’s not much artistic freedom I have with aperture, which has a hard, physical lutimit (largely dictated by how many thousands of dollars you’ve spent on your lens).
Plus, even if aperture could be pushed to the same extreme as shutter speed and ISO, the negative consequences aren’t that bad. Ergo, that’s why it’s generally safe to let the camera handle aperture.
This leaves me to think focus on shutter speed – hence, the term ”shutter priority mode.” If there is a lot of light in the night scene, the camera will bump up the aperture. However, I can bump up shutter speed instead (causing the camera to tamp down on aperture) – e.g. from 1/40s to 1/100s – because I care mostly about having a unblurred subject.
And if the light is great enough, I’ll bump the ISO down to 800, resulting in a less noisier image.
While I’m making these decisions, the camera is still at EV -1, which is fine unless I want to overexpose the night scene. And aperture will generally stay at the physical limit.
That sounds pretty complicated
In the above example, I’ve reduced the number of settings I care about to just two: shutter speed and ISO. And I don’t even need to worry about ISO under those conditions.
But it’s true, this is a far ways from letting the camera handle everything as it did in automatic mode. But I have much greater artistic control and I have a much better chance of getting usable images.
The next part of this book tackles shutter speed, ISO, and aperture in their own separate sections, in that order.
I chose this order based on the importance of the factor and how much real control you have over it. You can review the table in the ”big picture” chapter or read the condensed version below:
|What happens if you go too far?||How much control you have?|
|Shutter speed||Objects in your photo will be blurry, either because they, or your hands, moved while the shutter was open.||On most cameras, you can set the shutter speed to be as long as 30 seconds. Some cameras, you can leave it open indefinitely.|
|ISO||Your photos become noisy as fine details are smudged by random colored pixels.||Not much. Some cameras go to a ridiculously high number, like 25,600. But even on high end cameras, 1600 to 3200 might cause more noise than the average perfectionist photographer will tolerate. With cheaper cameras, ISO 800 can bee too far.|
|Aperture||It’s hard to go “too far” with aperture. The worst that happens is that anything not at the exact focal point range will be more out of focus.||Very little. The laws of physics reduce the range of possible aperture. To get a lens with an exceptionally wide apertures, you’ll have to pay a premium price. And even then, you have less freedom than you have with shutter speed.|
Are there artistic reasons for controlling the settings?
Yes, just as there were for deliberately increasing or decreasing exposure. Sometimes you deliberately slow the shutter speed because you want to capture light trails. And because you have a tripod. In a well-lit situation, you might have the aperture wide open – creating a shallow depth of field – so that only a few things are in sharp focus, keeping the scene’s clutter obscured by a creamy blur.
(there’s generally no reason to increase ISO to the limit; that’s just plain ugly)