When Lauren and I were in Stillwater on Sunday, we took some pictures down by the St. Croix River. (The body of water that serves as the border between Minnesota and Wisconsin.)
I almost always shoot at f/3.2 or wider. No particular reason, I just do. I’m actually trying to not do this as much, as not every image needs a creamy, blurry background. Since it was a sunny day, I had to keep my ISO low (100) and my shutter speed pretty fast so that all my images wouldn’t be blown out.
This one was shot at f/2.8 using my 50mm 1.4:
I like it because, while the background is blurry, you can still get a sense of the scene. (That I’m beside a river, and there’s a boat in the background and people walking along the river.) But you can’t see a lot of detail. And maybe I want to show exactly where I am, without changing the composition of my image.
There are two ways to do this. The first is by simply changing where I set my focal point. So for fun, I switched my focal point from the far left (bottom in this case since the shots are vertical) to far right (top):
In this image, my f-stop was actually f/1.8, but because what I’ve set my focal point on is so far away from me, more of the scene is in focus.
Depth of field is fairly mathematical. As in, you can find charts and graphs about where to set your aperture depending on how far you are from your subject. And to be honest I don’t understand all the math about it, but there are more variables than just your aperture. Your distance from the subject and on what part of the scene you’re focusing (and the rest of the exposure triangle — shutter speed and ISO) also all come into play. Math!
For a really clear example of how DOF can really change an image, I shot two exposures back to back, first wide open at f/1.4 and then with a much narrower aperture of f/11.
Quite a difference, right? I actually prefer the image with the narrower aperture (f/11), as you get a real sense of what it was like that day by the river. (In a VAN down by the RIVER. This is a required quote when you’re down by a river. RIP Chris Farley.)
So get out there and change up your aperture and play with manually setting your focal points (read your manual if you don’t know how!) and see what you can do!