rg
[EMAIL PROTECTED] wrote:
I'm not sure if there could be a technical reason for the discrepancy between focus and autofocus. Perhaps it could be the result of an incorrect diopter adjustment and a near-sighted or far-sighted eye? In regard to exposure, I generally set my *istD to overexpose by half a stop. That yields a pretty nice exposure under most circumstances. Finally, there's no such thing as a "correct" histogram. If you're shooging a scene with no highlights, the histogram may not extend all the way to the right, yet your exposure might be perfect. Similarily, blown highlights aren't always "wrong." For example, a strong backlight on water can create attractive specular highlights that are out of range. A photo with no dark shadows would have a histogram that doesn't extend all the way to the left. One with deep blacks might have out-or-range blacks. You have to judge with your eye. The histogram is only a guide. Paul
Reposting, since the first didnt seem to make it.
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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
