Focus Problem with 21mm and 16-45 Resoved..I think...

I had a problem with the 21mm Limited in conjunction with the K10D bodies as well as the 16-45 to a lesser degree. Here is what I surmised:

In my last shoot and in conjunction with the K10D and the 21mm Limited lens using a particularly difficult lighting for the AF sensor, Many of my images were out of focus on the models face and sharp on her feet. This is what I determined...

The problem with my K10D after extensive testing, seems to be a question of extreme low light conditions I utilise when shooting. After testing both bodies and several lenses, I have determined that the problem I was having was the difficulty associated with focus detection under adverse lighting and off axis subject matter. I solved the problem (I think), by doing a clutched manual over-ride. In tests, I have had about a 90 percent success ratio. As a result, I'll be using the K10D's for my next shoot called "Diva" for "Style Monte Carlo" Magazine. I'll post once the images are ready. I will shortly post "Citizen K International" once the magazine officially comes out.

The problem with Pentax in France is that their tech people have just started their orientation with the K10D and will not be prepared to solve these issues immediately. I will have to wait a few weeks to send them all of my material for a thorough bench test. I am sure that my problems are not exclusive to myself. However, for a certain type of lighting I employ, it is very taxing on the existing technologies, i.e. very low output lighting and severe angles to the subject etc.

Best Wishes
Ben

Here is a graphic representation of a typical type of lighting I use on occasion where the problem has cropped up. The Black area represents parts of the image that are very dark with no illumination. The Grey areas are parts of the image illuminated but not part of the main subject. The Green area is the lower portion or bottom of the subject and the Red could represent the face of the subject. This is more than a Graphic representation as it mimics the lighting conditions used during my shoots. As you can see, it challenges the AF sensor to only focus on the Red section. Also remember that I am shooting at the Red section from the floor at a distance of about 3 meters.

Quote:

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Originally Posted by benjikan

I solved the problem (I think), by doing a clutched manual over-ride. In tests, I have had about a 90 percent success ratio.
Best Wishes
Ben

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The ability to fine-tune the focus after AF is one of the best design features I've ever seen in a lens. As is probably obvious by now, I don't trust AF.

Why not just get the Katz Eye screen and be done with it?

I had done some jobs with one of the Olympus DSLR's. and the AF was HORRIBLE! A proper focusing screen should be an option for every camera!! (rant, rant, rant.....)