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09-04-2012, 09:43 AM   #1
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Focusing/framing problems on my IR converted K100ds

I've had my IR converted K100ds for two years now and have been happy with it until recently. Last month I was shooting with the DA*50-135 and I started to notice that with tightly framed subjects (in the viewfinder) the resultant image was shifted to the left a bit (an annoying bit to be clear). I first thought this was me but as I'm seeing this now all the time, it's clearly the camera and I'm also noticing that the focus is soft as well. (I could post pictures of this but the difference is between the viewfinder and the image.) AFAIK this wasn't a problem until recently but I don't have any older images that I could compare with because I only use this camera from time to time. So I'm wondering if any one else has seen an issue like this with their IR camera.

I'll add that this camera was supposed to have the focus adjusted for IR. Most likely it's got to go back to the shop but I'd like to know if this is a known issue or just if I'm the lucky one...

09-04-2012, 12:55 PM   #2
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It sounds to me as if the focusing screen has shifted slightly in the carrier. That's a cheap thing to check first.
09-04-2012, 01:26 PM   #3
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Hmm...I hadn't thought of that. The K100ds' screen is a PIA to open (I know, I've tried and failed and then succeeded). I'll give that a check. Thanks for that. In case that isn't it, any other ideas?
09-04-2012, 01:51 PM   #4
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Unless it is the mirror that is going off, and that means the repair shop for sure.

09-05-2012, 01:03 PM   #5
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What about SR failure or partial failure (one axis)? On later cameras you can shift the sensor to create that sort of framing shift. That might not affect focus though. You could try shooting in portrait or upside down to see if the shift changes with orientation.
09-11-2012, 09:04 AM   #6
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When the camera was converted the sensor assembly would have been removed, the IR-blocking filter detached and replaced with an IR-passing filter, and the whole lot reassembled. There's plenty of scope there for the alignment of the sensor assembly to be changed.

Regarding focus, normally the sensor assembly has to be moved backwards in order to achieve sharp focus in IR (compared to the same image in normal light). It is very unlikely that this was done sufficiently precisely to match the viewfinder image exactly - after all the viewfinder is showing visible light and the sensor is getting IR so the actual position of sharp focus has changed.

Is focus achieved correctly with AF?

On ones I've converted I've never even tried to get the viewfinder focus to match the sensor focus - it would involve many iterations of disassembly/reassembly/testing. The screen could be moved of course, but it would need to be away from the mirror so shims don't help. Unless there are shims to remove.

AF on the other hand can usually be tweaked to give good results with a few lenses.
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