Today I want to talk about something that might sound a little bit nerdy, but then again, if you've been listening to this podcast, then you already know that I'm a nerdy photographer. But this topic is really important if you want to get the best out of your gear. And that topic is testing your lenses. This came up quite recently because one of my participants was having some strange focus issues with her lens. I wasn't sure whether the problem was in her settings or the lens itself.
I'm usually pretty good at troubleshooting that, but this one really flummoxed me. So like any good photo geek, I went down the Google rabbit hole to see if anyone else out there experienced the same thing. I ran across a blog post by a photographer who was shooting that same lens, and he wrote something that made me stop and raise an eyebrow. He said, I'm not a brick wall shooter. What he meant was that he doesn't test his gear in controlled environments. He just likes to take it out into the field and decide how it performs based on real-world shooting.
That comment bugged me a lot. What this photographer was saying was that testing your lens by photographing a flat surface like a brick wall doesn't reflect quote unquote real-world photography. The problem is that real-world photography has too many random variables that you just can't control for and will give you false negatives. I'll get into that later.
When I tell people to test their gear, I usually suggest that they photograph something simple, like a garage door or even a printed test chart taped to a wall. Why? Because those surfaces have straight lines, contrast, and texture, which makes it easy to see how sharp your lens really is. And that kind of control testing is crucial, especially before a big trip like my recent trip to Antarctica. You don't want to get halfway to the end of the earth and realize your camera isn't focusing properly.
So this is what I had everyone do. Print some large black letters on a white sheet of paper and tape it to a flat wall. Make sure your camera is on a tripod, lined up so that the sensor is parallel to the wall. Then photograph the same target at every f-stop on your lens. If you're using a zoom lens, test it at a few different focal lengths, wide, mid, and full zoom. For example, on my 100-500, I shot at 100, 300, and 500 millimeters. What I'm looking for is the sweet spot, the aperture where your lens produces the sharpest image. And here's a tip, use a low ISO like 100 and good light. The idea is to remove as many variables as possible. Once you've taken your shots, bring them into Lightroom or whatever editing program you use, but don't touch them. Don't sharpen, don't adjust contrast, nothing.
Just zoom in and compare each image side by side. Eliminate the ones that look softer until you find the sharpest one. Then check your metadata to see what f-stop that was. And that's your sweet spot. This isn't rocket science. It's just careful observation, but it tells you a lot about how your lens is performing under various f-stops. And to be clear, every lens is different. What I found, both in my own testing and in results from others, is that the F8 rule, the idea that every lens is sharpest at F8, just isn't universal. Some Fuji lenses hit their stride right around F8. Nikon has a few that peak there too. But I saw some Canon and Sony lenses perform best closer to F4.0 and sometimes 5.6. And yes, things started falling apart at about F16 or F22. How much they fall apart really depends on the lens.
I even found a few lenses where the image softens dramatically past f11, while others hold up surprisingly well. The point is, you don't know until you test. Oh, and you'll also figure out whether or not your camera is focusing properly. Now, back to the brick wall shooter comment. The reason I advocate controlled testing is because in the field there are just too many unknowns. You might have motion, vibration, heat distortion, or lens flare, any of which can make your images look soft and lead you to blame your lens unfairly. I once had a participant test her lens indoors from her second floor condo. She swore she was on a tripod and was using a remote shutter release, but random images showed motion blur. Turns out her wooden floor was flexing ever so lightly when she moved and when her dog walked by. When she repeated the test on a concrete floor, the problem vanished.
That's why control matters. If you test in a controlled environment, you remove all those variables. Then when you're out in the field, you know what to expect. So if something is off, you have already eliminated at least one potential problem. What we're doing is we're applying the scientific method to photography, create a baseline and test against it. The other thing it allows you to do is when you're testing multiple lenses, you can compare quite directly which lens is working better than which.
So yes, I'm a proud brick wall shooter. I believe in testing gear in a controlled environment because it gives you clarity. It helps you understand your tools so you can trust them when it really counts. Because once you know how your lens behaves, where it's sharpest, where it falls apart, you can make smarter decisions in the field. And that's how you get better results more consistently. So do yourself a favor, tape something to your wall, grab your tripod and spend an hour testing your lenses. You might be surprised what you learn. Now you don't just have to shoot a brick wall. If you want a little bit more precision, you can buy devices online that create a target on a slant that will help you understand where your lens is focusing, not just sharpness alone.
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