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06-12-2009, 03:18 PM   #1
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Problem with split focus screen.

I recently received my Jinfinance split screen. I like the idea as it reminds me of my old Pentax film cameras and I have several older MF lenses and my K10D's stock screen is not MF friendly. I'm having a prolem with my new split focusing screen on my K10D. It is just plain out of focus.

When I use an AF lens the camera says it is focused (beeps) - but it is clear that looking through the eypiece that the focus screen is off. Pictures taken when I default to AF are spot on. When I take pictures in MF, the focus screen says I am in focus - but the pictures are not.

This is true for any lens I use. Everything from my Pentax 50mm 1.4 to a Tamron Adaptall 28mm 2.5 (with both a manual and an "A" adapter), to any other lens.

And yes I have adjusted the eyepiece to be in focus even though it has nothing to do with this problem. Any thoughts or ideas??

Thanks!

06-12-2009, 03:21 PM   #2
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Any chance you have the screen in backwards?
06-12-2009, 04:10 PM   #3
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Thanks for the idea. I should have mentioned that I have tried putting the screen in with the tab facing forward to both the left and to the right.
06-12-2009, 04:16 PM   #4
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Some of the Chinese/Singapore screens have a tape-like membrane protector that needs to be removed before use. From some reports, it is not particularly obvious. Maybe that is your problem?

Steve

06-12-2009, 04:22 PM   #5
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Thanks, but I caught that one early from reading some of the other posts.
06-12-2009, 05:01 PM   #6
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How far off are you talking about? If it's a small (but noticeable) difference, then it might be the case where your K10D's manual focus is front/back focusing. You would need to get appropriate shims from Pentax to calibrate it, though I recommend professional servicing.
06-12-2009, 07:17 PM   #7
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How much off am I talking? Good question. It is noticable to the point that if I relied on the focus screen all my MF pictures would be out of focus. However, all my AF photos are fine when I rely on the sensor. The focus screen has the 45 degree cut. That makes it very clear/easy to see when the camera should be in focus. The camera says it is in focus (beep - red dot flash) even though the visual evidence (through the eyepiece) would not yet consider it to be in focus. Yet the pictures prove the sensor to be correct.

I have (previously) done front/back focusing tests with several of my lenses in both AF and MF -- and I do not feel that I have a problem. When I go with the sensor -- my pictures are sharp. If I focus by eye with the jinfinance screen and disregard the sensor - then the pictures are simply out of focus. I do not believe it is a front/back focus issue.

Last edited by mstolt; 06-12-2009 at 07:17 PM. Reason: remove excess lines
06-22-2009, 01:08 PM   #8
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QuoteQuote:
mstolt: The camera says it is in focus (beep - red dot flash) even though the visual evidence (through the eyepiece) would not yet consider it to be in focus. Yet the pictures prove the sensor to be correct.

The red dot flash is not for in-focus designation, but the Green hexagon is. I have the same jinfinance screen on my K20--it is awesome. I use the 45 split (when the line is pefectly unbroken--straight) to determine focus. I sometimes use the prism too.

06-22-2009, 01:46 PM   #9
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QuoteOriginally posted by mstolt Quote
How much off am I talking? Good question. It is noticable to the point that if I relied on the focus screen all my MF pictures would be out of focus. However, all my AF photos are fine when I rely on the sensor. The focus screen has the 45 degree cut. That makes it very clear/easy to see when the camera should be in focus. The camera says it is in focus (beep - red dot flash) even though the visual evidence (through the eyepiece) would not yet consider it to be in focus. Yet the pictures prove the sensor to be correct.
I've noticed a similar phenomenon even with the stock screen for the K10d. However, usually the pictures prove the screen to be correct.
06-22-2009, 04:05 PM   #10
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Jeweltrail - I should have indicated that (for me) the red dot and the green hex are firing at the same point in time.

GeneV - Unfortunately and as the sample below will show the screen is wrong in my case.

I have attached two photos. The first is as the camera focuses (green hex - but the diagonal on the splitscreen is not a straight line).
The second is when the splitscreen shows the photo to be in focus (note- the green hex is OFF) and the photo is clearly out of focus photo.

Unfortunately I do not have a secondary camera to shoot through the viewfinder to show what I see.






Any ideas??
06-22-2009, 04:26 PM   #11
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I had the same problem with my second focusing screen on my K200D. I was front focusing everytime with the screen. I read up on the forums recently about the shims which was a godsend.

I took out the copper shim that came with the camera and cut out two paper ones (out of those sticky Yellow Post-It notes). Its alot better now. Ordering the shims from Pentax is probably a much better idea though.
06-22-2009, 05:06 PM   #12
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Pete- So did you shim the focus screen away or closer to the sensor to fix your problem?

It appears that the frame to hold the focus screen in the K10D does not have a removable shim. There is a flexible rail on the left and right sides which holds the screen fully pushed up towards the eyepiece / away from the sensor.

Thoughts?

Thanks!
Mark
06-23-2009, 05:48 AM   #13
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Mark

I have heard of shims for the K100 and K200 series cameras but not for the K10D.

Although I may (and probably am) wrong on tthis point if seems a little funny.

I have swapped screens 2 times in my K10D and never seen a shim. I use the Jinfinance diagonal split image and it is right on the money. I don't doubt the problem you are havinf, but I would suggest seeing if they will replace the screen.
06-23-2009, 07:58 AM   #14
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Mark:


As a rule, the K10 & 20 do not use shims for their focus screens, unlike other Pentax models. However, there are reports at this forum of people using shims to correct their focus screens on K10s for sure.

Best of luck!
06-23-2009, 09:37 AM   #15
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If you are unluckily supplied a focus screen with incorrect material thickness, you need to use shims to compensate.

If I remember correctly, if MF shows in focus yet turns out to be back-focus you need to add shim, vice versa reduce shim if front-focus.
You're stuck if need to reduce but there's no existing shim there to reduce

Hope this helps.

PS: shim is placed between the focus screen and the prism i.e. when you hold the camera in normal landscape orientation shim is above the focus screen (hope I got that right)

Last edited by Kguru; 06-23-2009 at 09:45 AM.
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