Inconsistent Focus

by Oliver Mews


Some lenses are crisp and sharp with your camera body while others are a little softer or even out of focus? Yes, welcome to the mysterious world of photography. I discovered two reasons why the auto focus is not working properly. One of the reasons was between the camera body and the lens, the other reason was behind the camera. Let me begin with the reason behind the camera: First I need to say that I always used the centered AF point to set the auto focus. Standing still with the camera in my hands, focusing with that centered AF point to the eye of the model, then panning the camera to the intended selected view (crop, picture section), double checking if everything is as intended, then pressing the button to capture the image – the outcome was between a master shot and a disaster shot. Some images were perfectly in focus while others went really wrong, especially with a wide opened aperture – and that’s what I really love. So I hardly learned that the reason was me (and the model too), because between setting the AF and panning the camera and pressing the trigger was enough time to tilt backwards and forwards. You can imagine that the photographer along with the model can sum up some inches in the worst case. Now I still love to capture people photos without a tripod, but now I’m aware that I really need to use the different AF points and push the trigger immediately after focusing the model’s eyes.



The second reason was more technical and harder to identify: The individual tolerances of my camera body and the prime lenses I use. Some lenses were crisp and sharp, but my 85mm f1.4 was really soft. But why? To make long story short: It was all about normal tolerances that I have to deal with in my photography gear. This was when we developed SpyderLENSCAL. This is a ruler with a scale that allowed me to focus on a chess board, while reading the defocus tolerance on the scale next to the chess board. All I needed to do was to use the AF fine adjustment in my camera’s firmware, to compensate the back- or front-focus. Just 20 minutes later I made my 85mm lens one of my favorites. And yes, we’re still “good friends” and from time to time we are renewing our “friendship” together with the help of SpyderLENSCAL. After we launched SpyderLENSCAL, we offered a free service at Photokina, Germany. We invited people to bring us their camera with one of their lenses. I remember that we tracked/logged 1043 camera-lens combinations. And believe it or not, we were able to calibrate and correct around 650 of them – some with considerable adjustments, but most lenses with smaller/minor adjustments. So I expected cheaper entry level DSLRs and lenses in that group of 650. But I was totally wrong. It really was a mixture of everything. The best was the photographer’s reaction, once they got back their cameras with an AF quality that was better than ever before.