Thursday, January 20, 2011

Testing AF systems

Okay, after reviewing information available on the internet about various famous camera brands and models, I've come to the conclusion that perhaps cross-type phase detection AF sensors occasionally have focusing issues with bright subjects, no matter what brand. I've read reaports about the 1D mkIII being problematic when introduced, with some owners requiring an entirely new mirror box to be fitted to the cameara. I've heard of front-focusing complaints from D300 users, D700 users, 5D users, and the list seems to go on and on. I'd like to test of few of these on my own, if anyone would like to contribute a camera body or two.

The test is simple; shoot a brightly colored and lit car at a wide open apeture, over a rough surface like gravel, from a tripod, and note for a series of 10 separately-focused photos, how many are focused right on the nose of the car. In theory, if the car isn't moving, the score should be 10 out of 10. Right now I'm not sure my D300 is doing that. Every so often, using Single Point AF, it will focus completely in front of the subject, resulting in a clear focal point ahead of where I've intended it to be. When shooting a car a distance away, this gross error can be large and extremely annoying. Especially when it's caused me to waste really good light, like what happened this past Sunday on a shoot.

So, in essence, I want to "audition" new AF systems. I want to know, over the last 5 years or so, who has produced the most accurate AF system. Then I want to purchase one! Immediately! I am tired of blown-focus photos.

And, lest anyone think that perhaps it's user error, I shot with two Konica-Minolta 7D bodies which were as durable and accurate as I could have wished, no matter what I shot or how ham-fisted my efforts were. I simply pointed and it nailed the focus. They weren't "fast" but they got the job done again and again. I expected this level of competence from the Nikon D300, and thus far have been disappointed. Time for a change...

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