To service, or not the k1ii

Started 4 weeks ago | Discussions thread
Roland Karlsson Forum Pro • Posts: 27,811
Re: To service, or not the k1ii

AwesomeIan wrote:

Florida Suse wrote:

AwesomeIan wrote:

At risk of sounding even more redundant, have you tripodded up and tested the AF using the viewfinder vs live view? As I understand it the live view uses different technology to get a focus lock and so if one works but the other doesn't you can assume the issue isn't with the lens itself.

Thank you for the suggestion, I don't mind at all the extra tips for doing this. I have only used the viewfinder for calibrating the lenses but, I haven't used a tripod, maybe that could be part of my problem. I figured I wanted to shoot the test chart the way I would really shoot the lenses and I rarely shoot using a tripod.

I worked a lot on this on Saturday and I'm totally spent and really over testing the focus in the lenses right now now, I really need a break. I think I got them where they need to be at the moment, I just need to get out to shoot to be certain of it.

A tripod is a good tool for this because it removes potential of human error. Another thing I like to try is to use a tripod and manually focus on something using liveview. If you still see soft focus after taking a picture I think it would be safe to say the issue is in the lens.

May I make a try at bringing some light on errors in AF.

There are two kind of problems.

  1. Sensor and measuring device are not in the same plane. This is camera related. It may be that the matte screen or the AF sensor is too near or too far away from the lens mount.
  2. The AF measurement is faulty due to the optic's geometry. The major problem here is focus shift, that the lens focus differently for the central rays and the edge rays through the lens. But, there might be some more stuff, e.g. color related?

So, 1 is camera related and 2 is lens related.

Lets say that you want to find the camera related (1) part of the front/back focusing. I think the easiest way to do so is to use a rather slow and very well corrected prime lens, e.g. an F4 macro lens. It is very unlikely that this lens have any front or back focusing. The reason for choosing a slower lens is that otherwise there might be some interaction with the maximum aperture of the AF optics.

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/Roland
Kalpanika X3F tools:
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