In the last lesson, I talked about shooting at the zoo under difficult circumstances and how to break the problem down into manageable pieces. One of the problems that TJ faced was that there was a fence between him and the subject. I promised to take a few sample shots through a fence and show what effects different apertures had on the image.
The following images were all shot with a Canon Digital Rebel XT and the Canon 50mm f/1.8 lens, also known as the nifty fifty. I chose it because I wanted to be able to open up the aperture in order to blur the fence as much as possible. Here are three sets of images that show how the fence looks from different distances at different apertures. I apologize for not finding more interesting subjects, but these were taken during a quick stop at the Port of Oakland when I was late for work.
In the first set, the camera is just a couple of inches from the fence. The camera was in aperture priority mode, and the four shots were taken at f/2, f/4, f/8, and f/16. As you can see, at f/2, the fence blurs so much that it’s essentially invisible. At f/4, you can start to see the fence blurring parts of the image. At f/8 the fence is quite visible, and at f/16 it’s almost sharp.
This time, I’m standing about an arms length away from the fence. At f/2, the fence is just a blurry grid. At f/4 it starts to look like a fence, at f/8 it’s clearly a fence, and at f/16 it’s fairly sharp.
In the final set I’m standing about five feet away from the fence, and also at a slight angle. At f/2 the fence is a blurry mess, at f/4 it starts to sharpen up, and at f/8 and f/16 it’s sharp enough to work as part of the image rather than being a flaw.
Conclusion: if there’s a fence in your way, figure out what you want to do about it and adjust accordingly. If you want to make the fence disappear, get as close to it as you can, and open up your aperture as wide as possible. If you want to use the fence as part of the image, back up a bit and stop down.
3 responses to “Shooting Through a Fence”
In the first set of pictures, when you were just inches away from the fence… the smallest red containers on the left side of the picture, have white markings on them at f/2. But when you get up to f/16, it’s apparent that the fence wire obscures this part of the container. How is the camera seeing those markings at f/2? It appears that the camera has x-ray vision and is seeing right through the wire! LOL
How to explain? Hrmm.
Imagine that you’re looking at a scene through a drinking straw. If there’s something right in front of the straw that blocks the scene, you’ll only see that blocking object (oh, say, a fence) and not what’s behind it. Take the drinking straw away, and if the obstacle is small you’ll be able to see around it.
In essence, I think that’s what’s happening with this shot. When the aperture is small, the lens is basically drinking light through a straw. When it’s wide open, it can see around the fence to pick up what’s behind it.
That’s my best understanding, at least. I don’t have extremely high confidence that I’ve given you the *right* answer this time, but intuitively it sort of makes sense.
This also works nicely for shooting through dirty glass. An unfortunate reflection this morning provided me with a very nice demo pic: