I only shoot manual mode for my nature photography, and I’ve done it this way for years. No, it’s not because I want to look like a pro (though that’s a cool side benefit!). I shoot manual mode because it’s easier!
When you shoot in any of the priority modes (e.g., aperture priority, shutter priority, or, yes, manual mode with auto ISO), you’re letting the camera make decisions for you. With aperture priority (A or AV), the camera varies the shutter speed to obtain the “proper” exposure. In shutter priority (S or TV), the camera changes the aperture according to the scene. And, of course, if you shoot manual mode with auto ISO, the camera chooses the “correct” ISO value. These modes often get you in the ballpark for a good exposure, and this is exactly why people think that they are easier than manual mode. However, if you want to understand what’s really happening in the priority modes, you need to wrap your head around a few tricky concepts.
First, the camera’s meter sees all tones as middle gray. Take a picture of a black square, and your camera (in any of the priority modes) will try to make that black square gray. Same with a white square; your camera wants to make it gray. You need to outwit your camera by using exposure compensation (EC). To make the black square black, you can set an EC value of -2 or -3. And to make the white square white, take your EC up to a value of +2 or +3. A little convoluted, right?
And it gets more confusing. What if you’re photographing a white bird such as a cattle egret (Bubulcus ibis) surrounded by an expanse of dark water, as shown here? Even though your subject of interest is white, you’ll have to dial in a negative EC value. Why? Because if you don’t, the camera will see all of that dark water and try to make it gray, which will result in an overexposed egret. If you photograph a black bear (Ursus americanus) in a snowy environment, you have the opposite problem. The camera will woefully underexpose the bear as it tries to make the snow gray. Even though your subject is dark, you need to add positive EC to keep the snow white and the bear properly exposed.
But wait, there’s more! If you’re using a zoom lens, you might want to take one tight photo of your egret or bear and another photo where you zoom out to include more of the environment. If you do, the priority modes will have trouble keeping a consistent exposure for your subject. And if you shoot action, say birds in flight or mammals running across a field, priority modes will give you inconsistent exposures as your subject moves against lighter or darker portions of the background.
Imagine you’re photographing ducks flying around a pond in beautiful light, such as the northern pintail (Anas acuta) shown below. If you shoot in any of the priority modes, the camera will meter the scene differently as your duck flies against the bright sky, then descends through a grove of light green trees, and then comes in to land in a patch of dark blue water. The result is that the exposure on your duck will vary from shot to shot. Sometimes it will be well exposed, and sometimes it will be over- or underexposed. There is no way you are going to be able to change EC values to fit each of these situations as you shoot off a rapid-fire burst, all while trying to keep a flying duck in your frame.
Since the light on the duck is the same, there is actually one correct exposure for all of these scenarios. What if, instead of worrying about the tone of your subject and the tone of your background and how much relative space each occupies in the frame, you simply concentrated on exposing for the subject? That’s what manual mode allows you to do! Since you are in control of all three exposure variables (shutter speed, aperture, and ISO), exposure compensation no longer applies. You set your camera so that your subject is well exposed and concentrate on behavior and composition!
Here’s how I do it. Pretend I’m out photographing a keel-billed toucan (Ramphastos sulfuratus) on a nice branch in the rainforest.
I start with the aperture and ask myself two questions. How much depth of field do I need for my subject and how far away is my background? I may want lots of depth of field (say f/16) for my subject, but if my background is fairly close, I’ll get too much detail, and the background will become distracting. So, perhaps f/8 will give me enough depth of field on the toucan while keeping a pleasing background.
Now, on to the next two questions. What shutter speed do I need and what kind of light am I shooting in? I might want a super-fast shutter speed like 1/8000th of a second, but if I’m shooting in dim rainforest light, that will mean crazy high ISO values that would compromise my image quality. So, I might back off and say, you know what, 1/2000th of a second will be plenty fast.
Next, I work my ISO dial until I obtain a good exposure for my toucan. Perhaps I’ll settle on ISO 1000.
I can get fancy and try to meter off of a middle-toned subject, or I can use the live preview in my mirrorless camera or take a shot and review my exposure with my DSLR. In any case, I can start to zoom in and out for tight shots and environmental portraits with the confidence that I have my toucan well exposed no matter what is going on with the rest of the scene. And if the toucan takes off and flies, I’m good to go and can blast away as it moves against different backgrounds!
I urge you to give manual mode a try in 2023. I think you’ll find it easier and more precise.