In my previous post, we focused on how important it is for the bird photographer to know how to quickly and efficiently select the different AF area selection modes and AF points. In today’s post, I will discuss the benefits and uses of Aperture Priority (AV) exposure mode and Manual exposure mode and when to use each. However, to make sure we are comparing apples to apples, lets first identify the Canon and Nikon equivalents and then we will define each mode and their possible use in bird photography.
Canon & Nikon Exposure Modes
Program Mode (P) vs Program Mode (P)
Shutter Priority (TV) vs Shutter-Priority Auto (S)
Aperture Priority (AV) vs Aperture-Priority Auto (A)
Manual (M) vs Manual (M)
While many people are probably already familiar with the basic gist of each of these modes, let’s take a look at how each one applies within bird photography.
Program Mode (P)
In this mode, the camera selects the aperture (f-stop) and the shutter speed. If you use this mode ever for bird photography, you have relinquished every aspect of control that you need to photograph birds well and creatively. There is really never a time when you should shoot in this mode (except for those times when we have accidentally moved the control dial and don’t realize we are shooting in this mode)! This might be fine for snagging quick Christmas shots at grandma’s house but I don’t understand spending the money on a nice DSLR camera and then never bothering to learn how to shoot in other modes.
Shutter Priority Mode (TV or S)
In TV mode, the user selects a given shutter speed and ISO (unless you are using auto ISO which I do not recommend) and the camera selects the aperture. Quite often I read or hear of bird photographers recommending TV mode to other beginning bird photographers on the basis that you want to use it to stop motion by selecting a fast enough shutter speed. Of course, the shutter speed needed to stop a heron in flight (say 1/800) and that of a swallow (say 1/2500) can vary quite a bit.
I can honestly say I never use TV mode because for me, controlling the depth-of-field with the correct aperture is more important and I can control my shutter speed by raising my ISO if need be. Sure, you might stop motion of a flying Heron by using TV and setting your shutter speed to 1/1000. But let’s say you have your ISO set low at 200 or the like. What if you end up with a very large aperture like 2.8 and your AF point snags a part of the wing? You have no hope of having the bird’s eye in sharp focus. Using AV mode solves these issues for me.
Aperture Priority Mode (AV or A)
In AV mode, the user selects a given aperture (f-stop) and ISO and the camera selects a shutter speed. This mode is excellent for bird photography because we should be very concerned about having the proper depth-of-field. If we are just diligent, we should have no problem insuring sufficient shutter speeds by using proper stabilization techniques, an appropriate ISO and learning to read light. When using AV it is important that the user learn how to apply exposure compensation.
Manual Exposure Mode (M)
In the Manual Mode, the user has complete control over all aspects of exposure: shutter speed, aperture, and ISO. This allows you to be in complete control of your camera. While this might seem intimidating, I can assure you that with a little learning and a little practice, you will be smarter than your camera in no time! You do not have the ability to apply exposure compensation in Manual Mode since you are in complete control of exposure.
Manual vs Aperture Priority Mode – When Do I Use Which?
So how do I know when I should use Manual Mode and when should I use AV Mode? For me, it boils down to this simple determination. When the tonality of the background is changing and the light remains fairly constant, I shoot in Manual Mode. When the light is changing constantly and/or the tonality of the background remains constant, I will work in AV mode using exposure compensation. Now, it is important to understand that I use evaluative metering 100% of the time. This determines how the camera body reads the light reflecting off the scene and determines exposure. Some photographers might suggest to use spot metering and stay in AV mode. Well, how likely are you to keep the spot on a flying bird all the time? If you can, you are way better at panning and following birds in flight than I!
Let’s say you are using AV mode (amount of exposure compensation is not important for this illustration) and you start photographing a Great Egret in flight and in the first frame, the background is the sky and your exposure is spot on. What will happen when that same bird drops out of the sky below the tree line? The camera will end up dropping your shutter speed significantly because the tonality of the sky was much brighter than the tonality of the trees. What will result is a very overexposed (and probably blurry due to low shutter speed) Great Egret. Has this every happened to you? It use to happen to me regularly. What made the difference for me was reading Arthur Morris‘ book “The Art of Bird Photography II” which is available as a CD and well worth the price. He taught me when to use Manual Mode and when to use AV Mode.
Here is a series of images of the same Great Egret on different backgrounds. Without manual exposure, the camera would have selected a very slow shutter speed for the first shot with the darker background leading to a blurry image and an overexposed subject.
I would encourage you to begin to pay attention to the tonality of an area you will be shooting and ask yourself if the lighting and the background tonality are remaining constant or changing? This is a great exercise to do every time you go out.
Go out to your local park or a place where you can find some birds to practice your manual exposure techniques. Don’t wait until you go to some exotic birding destination and try to learn a new technique!