DoF & Infinity
Photographers are challenged by all they read about Depth of Field and how to apply what they’ve read. Personally, I still prefer to think of it of how I was taught it back in the dark ages, Depth of Focus. You might want to get our FREE iBook Photography FUNamentals if you’re feeling frustrated by DoF. At the moment, I want to talk about DoF and infinity. While in science, infinity has one meaning, in photography it’s much easier to visualize. All you have to do is set you lens to infinity and look through the viewfinder, you’ll see what is and what isn’t in focus. In this example, the Tetons are miles away from the camera and whether shooting with a wide angle (above here using a 18-35AFS) or long (below 80-400), closing the lens down to gain DoF is a waste of shutter speed. Infinity while mathematically has DoF, in practice, you gain nothing.
This is photography so of course, there are caveats. In both of these photos, there is nothing else between the camera and the subject that we want in focus. For example, in the top photo, if we put a person in the foreground to take their portrait, than yes, DoF matters very much. Shooting with a wide lens, DoF is pretty simple. Shooting with a long lens, DoF can be a challenge. But I’m not talking about that. I’m talking about the subject being at infinity and the belief that shooting at f/32 is going to help with the sharpness. It will not, you can shoot at f/5.6 as these were and be good to go. You can test this for yourself and I hope you do. It might help you move down the DoF road and make it work for you. In this case, opening up the lens, having a faster shutter speed and just a tad more fun.