This topic has been on my mind for a while. And I figured it would be a handy thing to keep in mind if you’re looking for sharp quality images. Someone I know expressed this issues not that long ago and I mentioned that their autofocus might be back/front focusing. In order to diagnose a problem you need to know a little about how a dslr’s autofocus works. I came across this site, Tim Jackson’s Nikon D70 site, a long time ago that gives good insight into the camera inner workings . And I just found another that gives a bit more info on the topic, Jeffrey Friedl’s Blog. Both sites even provide a focus chart you can download and print to perform the necessary test. I won’t go into the details of the test since i’d just be repeating what they have written so well already. One other thing you can also look into buying is a product called Spyder Lens Cal which is designed for just this reason. But the charts you can download do the trick.
Now originally if there would be a problem you would have had to send the camera out for adjustment. Meaning it would cost you to have it repaired and you’d be without a camera for a bit. Now things are a bit simpler, with lens micro adjustments being available in your camera’s menu. On my particular camera (canon 5dmII) you can either adjust the focus universally or by each lens. Which was necessary for me since each lens I had needed unique adjustments. I have yet to put the results to work in real world scenarios but so far so good. I just feel better knowing i’ve looked into it, since I had a few shoots that were slightly soft focussed.
Like i said, I tested all my lenses. Which if you have more than one, you would need to do the same to see if the camera has an issue or the lens. There is always the possibility that the lens elements may be off which would cause improper focus or even uneven focus across the frame. One more thing i would suggest. Don’t compare your focus to the results from a different camera, particularly one with higher resolution. If you are working with an APS sensor camera, the pixels are more tightly packed compared to a full frame. Which means you would have more grainy/pixelated images and less crisp and clean results. You could easily mistake the graininess for soft focus.
Not the most thrilling topic to read about, but something to consider.

Ok, that was petty morning entertainment. Back to work.

