Probably not a very helpful post, but I experienced the opposite when I had an ist D. With a Sigma 28-70 2.8 EX, AF would constantly backfocus, MF was tack sharp. With the F 50 1.4, and FA 28 2.8 AF MF worked perfectly. Sounds like a rather bizarre problem. Hope you get it sorted out soon.
Cheers, Ryan ----- Original Message ----- From: "Gonz" <[EMAIL PROTECTED]> To: <pentax-discuss@pdml.net> Sent: Thursday, February 24, 2005 7:26 AM Subject: Help! *istD problems (repost) > Reposting, since the first didnt seem to make it. > > > ---------------------------- > I need some help with my *istD. For the longest time, I've been having > problems with my pics being quite soft wide open. I thought that it was > just because the lens was wide open. I have alot of manual focus > lenses, which I use often. The problem showed up mainly with them, so I > went back to look at some of the pics more carefully, and I noticed a > pretty consistent pattern. There were areas of sharpness alright, but > not where I wanted them to be. I was consistently back-focusing. So I > did some tests. I mounted my FA* 85 1.4 on the camera, set it on a > tripod, and proceded to make some careful experiments to see if I could > put the blame where it belonged, on me or the camera. > > The setup was your typical measurebating focus test setup. I had a ruler > at an angle with a target off to the side of it where I focused. I took > pictures with and without autofocus. The result: no matter how > carefully I manually focused, the autofocus was always right on the > money, and I always back focused. I adjusted the diopter after > autofocusing to see if I could match the camera's focus point, took my > glasses off, put my glasses on, danced around the camera, but no matter, > I always back-focused. What is going on here? Doesnt the autofocus see > the same thing I do? Or is something mal-adjusted somewhere? When I > look through the viewfinder after I auto focus, it seems to be in decent > focus, but it looks pretty much the same as when I focus manually. If I > then switch to manual focus and get it out of focus and back in and take > the pic, it is back-focused! Am I going blind? > > The second problem is that I seem to always be adjusting exposure > upwards in the PS raw program, usually between .5 and 1.0 stops. What > should a "good" histogram look like? My camera seems to like to > underexpose, in my opinion. Is this normal because of the blown hilites > problem? When I bring in the raw pics into PS raw, the histogram > usually shows no pixel values above the halfway point, yet if I look at > the histogram using the *istD lcd panel, it seems to show some luminance > values, although very few of them, up to the max luminance value. Why > is there a discrepancy? I am going to try the same thing with Pentax > raw and see if the histogram matches PS raw to some degree. I know that > PS camera raw breaks up the values into RGB components, while Pentax > combines them into a single histogram, so there might be an > apples-oranges thing going on here. > > Anyhow, I would love to tap the collective PDML brains to see what I > need to do here to solve some of these technical issues. Thanks ahead > of time for any help you can give me. > > > rg > >
