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.
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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.
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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.
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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.
Stop Shooting Auto! 