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05-18-2009, 06:02 PM   #1
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Pentax-M f1.4 50mm lens & K-10D

This issue has me scratching my head. I have a very nice 50mm SMC Pentax-M f1.4 prime and a 28mm SMC Pentax-M f3.5 prime lens and I'm having an awful time getting the 50mm lens to focus on my K-10.

Originally I was using the standard Pentax focusing screen and was unable to get it to focus clearly, so I ordered a split image, multi prism focusing screen (Chinese) and today installed the new split image, multi prism focusing screen in my K-10. I cannot get the 50 to focus with that screen either, It looks like it's in perfect focus in the view finder but the picture is blurry.

I use the 28mm and focus the same and the photos all appear very sharp. Does anyone have any idea what might be the issue? Is it possible that the elements are messed up? It's been to the camera doctor to repair a loose lens barrel (where the filter screws in) and I asked him if any of the elements were loose or out of alignment and he said no. I'm at my wits end!

05-18-2009, 06:07 PM   #2
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You may need a shim of a different size. Paper cutouts work.
05-18-2009, 06:14 PM   #3
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QuoteOriginally posted by jimH Quote
It looks like it's in perfect focus in the view finder but the picture is blurry.
Does this happen with all aperture settings?
05-18-2009, 06:35 PM   #4
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Did you test it on all aperture? Focus screen didn't change the focus on the camera. To test it, set focus to infinity and shoot at far distance, if it still bury, that means the lens is not working right. Also, the camera should also give you a focus confirmation. Also at F1.4, the DOF is small, so any little movement will change the focus point.

05-18-2009, 07:03 PM   #5
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It is a tricky lens full open. Very shallow depth of field.
05-18-2009, 10:10 PM   #6
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What he said. My 1.4 and 1.7 focus great, though I have to get it correct. Not much error margin.
05-19-2009, 12:41 AM   #7
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If you can focus with the 28 but not the 50 then the lens is knackered !

Whoever repaired it for you may have re-assembled it incorrectly.

You can always use it as a paperweight andf get another one from eekbay
05-19-2009, 06:28 AM   #8
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Thanks everyone, you've given me some things to try out.
jimH

05-19-2009, 06:59 AM   #9
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QuoteOriginally posted by SOldBear Quote
Does this happen with all aperture settings?
Mostly at wide open or a couple of stops down. I did take it out this morning and focused to infinity and did several shots, wide open, f2 f5.6 f8. They seemed to be OK. Brought it back in the house and turned on the flash and set the aperture at about f5.6 and f8 and did a flash picture from about 5 feet away from a horsehair vase and it seemed pretty good. I'm guessing that it is a depth of field issue since most of my previous testing was at a 3 to 4 ft range at wide open, under indoor lighting. I believe that at the very best the lens is a little soft in the sharpness area. Much softer than my 28mm, which seems very sharp.

thanks again for your help as well as everyone else's help.

jimH
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