We’ve got great automation in our cameras. Metering is generally terrific with lots of options to control exposure. So why do I use Manual Exposure Mode for bird photography?
I’m using Aperture Priority for general photography and other exposure modes are the exception. For me, depth of field is everything because I either want subject isolation or background detail. I choose the depth of field desired for a situation and the appropriate aperture – the shutter speed is automatically calculated and I use base ISO unless I need a faster shutter speed (and then I increase ISO as needed). Depending on the scene and subject, I may also need a specific shutter speed but I choose aperture then shutter speed and finally ISO. If my scene is a little light or dark, or if I have blown highlights, I dial in exposure compensation as needed. But with bird photography, I often use manual exposure mode rather than aperture priority – especially for birds in flight. Here’s why.
For birds and most wildlife, I typically start by choosing my aperture. Usually I shoot wide open or slightly stopped down to isolate the subject with a soft background, with the side benefits of a fast shutter speed at as low an ISO as possible. Subject isolation is important, but sometimes lenses perform a little better stopped down 0.5 to 1.5 stops. Long lenses are usually intended to be used wide open, but when you add a teleconverter, or need a little more depth of field, you probably will stop down from the widest aperture to obtain best performance.
It’s important to note that I’m also trying to keep the shutter speed up – usually 1/1000 sec or faster for moving birds. This is consistent with a wide open aperture or only stopped down slightly, then increasing ISO as needed until noise is problematic and I need to make trade-offs.
For those that use Auto ISO, there are additional considerations. Auto ISO is a useful tool when the light on the subject is changing. As with Aperture Priority and Shutter Priority Modes, Auto ISO is a semi-automated exposure mode. With Manual Exposure and Auto ISO, you can set the aperture and shutter speed and allow the ISO to float. Unfortunately, Auto ISO makes the camera respond the way it would in other semi-automated modes by adjusting exposure, and you would have to adjust exposure compensation to get correct exposures. If you have constant light on the subject and are using Manual Mode as described here, I would avoid Auto ISO. It’s a useful tool for other situations.
Light on the subject
In open areas, the light on the subject is usually constant. Light clouds or changing light poses a different issue, but if the light is relatively constant the exposure values don’t need to change. So manual exposure mode can be used to lock in exposure settings to produce accurate exposures for a wide range of subjects and compositions. If light on the subject is not changing, I don’t need the camera to adjust exposure.
The color of birds can have a big impact on exposure. Birds with white or black coloring are especially difficult because they are at the extremes of your exposure. It easy to blow out highlights or underexpose dark areas and shadows to the point where they can’t be easily recovered. The camera’s meter exposes to a neutral based on 18% gray. A white bird will be underexposed and look gray, while a black bird will be overexposed and be a dark gray – and neither is right. The problem is worse when you have extreme contrast on the same bird such as light areas in sun on a dark bird, and a stop of overexposure is very difficult to recover. The exposure of a neutral gray card would be the same regardless of the color of the bird, so manual exposure simply locks in the correct values.
In this image, the bird has a neutral tone but is lit by full sun against a dark reflected background. In automated modes without exposure compensation, the bird tends to be overexposed with blown highlights. Manual exposure mode locks in the exposure for a sunlit bird regardless of the background.
Size of the subject in the frame
A small bird in a distant landscape essentially becomes an exposure for the landscape. Zoom in or move closer to that same subject, and the color of the bird starts to influence the exposure read by the camera. Fill the frame with that same subject, and the color of the bird or even parts of the bird dominate the exposure. If a bird starts out far away, and gradually moves closer until if fills the frame, you need to maintain the same exposure settings – either with exposure compensation or just using manual exposure. The size of a neutral gray card makes no difference in the exposure if you are metering on the gray card. Manual exposure locks in the correct exposure value regardless of how you frame the subject.
The first image in this pair shows a yellowlegs that is small in the frame, so the overall exposure is based on the green background. The second image shows a very dark glossy ibis that is large in the frame, which would tend to require exposure compensation in an automated mode.
The background is the counterpart to the subject filling the frame. The amount of background in the frame, and the lightness or darkness of the background can have a large impact on exposure. Consider the same subject with dark bushes as a background – and then consider it with the light blue sky as a background. In semi-automated modes, the bird will tend to be overexposed with a dark background, and underexposed with a light sky. Manual exposure locks in the correct exposure value so changes in the background don’t cause a change in the exposure.
This pair of images shows the same birds in the same pass just a few seconds apart. Only the background has changed. But with an automated mode, the difference would require a full stop of exposure compensation to account for the light on the subject being unchanged.
Manual exposure mode eliminates all these issues. It provides a constant exposure value as long as the light stays the same. If the light changes, you probably need to make adjustments. Let’s look at the most common ways to set the exposure.
Using Manual Exposure
If you normally use Aperture Priority, an easy way to find the right exposure settings is to simply meter the scene in your normal manner and take a test shot. If necessary adjust exposure compensation and take additional test images until your exposure is correct. Then set the camera in Manual mode for the same aperture and shutter speed settings you found to be correct. The exposure indicator may or may not be centered. Normally it indicates a correct exposure, but it depends on all the variables that influence whether your exposure is correct or not – especially framing the scene. So it is only used to provide perspective on the impact of changing light and make additional quick adjustments.
Another common way to determine the manual exposure settings is to meter the subject or another element in the same light and adjust if necessary. Ideally you would use something in the same light that has a neutral tone – a gray card, foliage, etc. This provides a good starting point for the correct exposure and then you will take a test image to confirm the settings. If you have a pure white subject such as a great egret, you can spot meter on the white subject and add +2 stops as a starting point. An easy technique if you want to photograph a pure white subject at f/4 in manual exposure mode is to adjust your aperture two stops before you spot meter. Set the aperture for f/8 and meter the scene to find the shutter speed. Then change the aperture back to f/4 thereby making your two stop adjustment.
There is no perfect exposure mode for all situations. The camera does a fantastic job with automating functions and freeing you up to make well composed images. But Manual exposure mode does have a place, and is frequently my choice for photographing birds. It has limits and would not necessarily be my choice in changing light, but when light is consistent, it’s a good option.
We’ve discussed the use of Manual mode for bird photography, but the same issues and techniques apply to other situations. For example, Manual mode is useful for sports, especially when team colors are different or backgrounds are changing. It could also be used for weddings where the bride is wearing white or ivory and the groom is wearing black or other dark colors. Consider manual mode to be one of your tools and use it when appropriate.