One of the things that photographers have to do is to learn how to effectively hand-hold a long telephoto lens. The reason this is necessary is that there are times when using a tripod (the preferred technique with any lens longer than 200mm) just isn’t possible. I’m not talking about the times when you are too lazy to go get your tripod (Yes, it happens to me as well!), I am talking about the times when a tripod is either not allowed- usually in a crowed spot with limited space- or when it is physically impossible to set up and use a tripod- usually in a crowed spot with limited space. On a boat is one common example when tripods are often not practical to use.
So let’s pretend you are on a boat and want to use your 300mm f4 lens to photograph a bald eagle perched perfectly on a snag against blue sky. What is the best way to set up your camera?
The first thing to do is to realize that shutter speed is your biggest concern. The higher the shutter speed the less the picture will be degraded by movement. The old rule of thumb is the minimum shutter speed is at least equal to the inverse of your focal length so for a 300mm lens you need at least 1/300th of a second shutter speed to get good results. 1/500th or 1/1000th will yield better results but you have to have at least 1/300th with a 300mm lens.
So how do you assure yourself that you will get the highest possible shutter speed? Use the widest possible aperture to get the minimally acceptable depth of field. This will, by definition, get you the fastest possible depth of field. And how do you get the widest possible aperture? Ask yourself how much depth of field you need, set your camera at that figure and using Aperture Priority, blast away.
That’s right, by using Aperture Priority, you will assure yourself of getting the highest shutter speed because you will be using the widest (fastest) possible aperture. I know it sounds counter-intuitive but if you think about it, it makes perfect sense.
In practical terms, most of the time you are hand-holding a long lens your subject is pretty far away. This means you don’t need to use f11 or f8, f5.6 or even f4.o will work just fine. (Remember, as your subject gets farther and farther away your focusing point approaches ever closer to infinity. Once you are on or near infinity depth of field becomes nonsensical. ) So now all you have to do is crank up your ISO so that your shutter speed goes beyond the rule of thumb threshold.
For the bald eagle I shot a Nikon 300mm f4 at f5.6 at ISO 1250 and a shutter speed of 1/1000 of a second. If there were any less light I would’ve shot at f4 and maybe cranked up my ISO even more to get similarly fast shutter speed. Remember, I am on a boat which is moving forward and moving up and down in the waves. Plus I am swaying around just standing there! the more shutter speed the better! Then the trick is to just find the bird in the viewfinder and get the autofucus point on the bird.
So anytime you want to be sure you will have the fastest possible shutter speed figure out your minimum required depth of field and set you f-stop accordingly. Then shoot in Aperture Priority and blast away!