Aperture Priority Mode for the Fastest Shutter Speeds

I was taking images of ruby Throated Hummingbirds the other day in variable lighting and another photographer asked me how I had my camera set up. It took awhile for me to explain my answer so they understood. What I do may sound counter intuitive, but it works.

When I need to shoot with the fastest shutter speed I can get, I switch my camera to AV or Aperture Priority mode. Yes you read that right. I don’t switch to Shutter Priority or Manual Mode, but Aperture Priority. Let me explain how I set this up, and why it works.

As I’m sure you are aware, there are three sides to the exposure triangle that we can adjust to get the correct exposure. they are Shutter Speed, Aperture, and ISO. I generally like to keep control of at least 2 of these. SInce I am letting the camera pick the shutter speed when I am in AV, I will select the aperture and ISO. Here’s how.

  • Aperture Setting: Since I want the fastest shutter speed, I will set this at the largest aperture that I can. This may be f/2.8, f/4, or f/5.6 depending what lens I am currently using. The number is not really that important to the other settings, just make sure that you are using the largest aperture you can. By choosing the largest aperture, you then can use the lowest ISO for the lowest noise, and the fastest shutter speed.

  • ISO Setting: Since I am letting the camera determine the correct shutter speed, and I have the largest aperture my lens is capable of selected, the ISO setting is very important to make this technique work. You have to select an ISO that will allow your camera to select a shutter speed that is in a range that will be appropriate for the situation. This is where experience, and knowing your camera and subject comes into play.

    • You need to know what the acceptable max ISO is for your camera. That is the highest ISO that will give you grain that you can live with. This is different for every camera, and every photographers taste. For me, on my Canon 5D MKiv, I will go up to ISO 6400. There are techniques to control the grain at higher ISO, but that sounds like a good topic for another post! The important thing here is to know what your limit is for the camera you are using.

    • You also need to know what shutter speed range is correct for your subject, and the shot you are trying to create. Since this started with my taking shots of hummingbirds, I will stick with that. For hummingbirds, It’s all about getting a nice blur in the wings to show motion, but having a fast enough shutter speed to freeze the rest of the bird. This will be @ 1/1000 sec. in most cases. So how do I pick the appropriate ISO? I will take an exposure reading off of something that is in the same lighting conditions that I expect the subject will be in. Grass, or green leaves work great. I then adjust the ISO to a level that will give me @ a 1/1000 sec shutter speed.

Now that you have the aperture and ISO set, your camera will give you the fastest shutter speed possible to give you what it thinks is a correct exposure. You may be asking; But what if the lighting changes on your subject, or the background? How do you quickly override the camera’s exposure? Both good questions. What I do is use Exposure Compensation to quickly make adjustments to the exposure, without changing any settings. On my Canon 5D MKiv, I can quickly turn the command dial on the back of the camera to under or over expose the exposure the camera has calculated.

Here is an example. Let’s imagine that I have set up my camera as described above, and suddenly the hummingbird flies into a bright shaft of light coming through the branches, but the background is still in shadow. This will probably cause the camera to overexpose the hummingbird, since the bright area, the bird, is too small to affect the overall exposure of the entire frame. All I have to do is turn the command dial three clicks counterclockwise to override the camera’s exposure by -1 stop. I don’t have to take my eye away from the shutter to do this, and since I know that every click on the dial is 1/3 of a stop, I can make an appropriate adjustment fast enough to even keep up with a hummingbird!

This technique takes practice, and a very good understanding of you gear, and how to use it, but once you get use to it, I bet you find it one of your go to techniques when the fastest shutter speed possible is what is needed to get the shot.

If you have any questions on this technique, please leave a comment.