Flange correction in old lenses

TomGarn · 10-19-2014, 09:47 AM

I found out that sharpness gets lost when pulling back my zoom to wid angle.
Lense: Pentax SMC A 35 - 105 / 3.5

A fine lense I use for video mostly - and with manual focus only of course.
FLANGE must be the problem - more so because the zoom-ring moves very tense
and also very close to the ring with f-stops - and very near the camera body. So also it
happens again and again, that this small button used to fix the A-position gets unlocked then.

The Pentax service in Hamburg refuses to look at it - maybe it's to old and to cheap for service ?
And I know in broadcast-video-cameras the flange must be looked after each change of lense (for best)

Anyone knows how to do it himself ? With video-cameras you do it with a SIEMENS-STAR graphic,
comparing tele and wide-angle ... we have a special knob to twist and adjust...
But how to do it with a photo-lense ? Ist there a chance ?

Last edited by TomGarn; 10-20-2014 at 08:26 AM.

kh1234567890 · 10-19-2014, 10:18 AM

Originally posted by TomGarn

I found out that sharpness gets lost when pulling back my zoom to wid angle.
Lense: Pentax SMC A 35 - 105 / 3.5

This a common problem with this lens. Mine is beginning to go that way. Apparently due to wear on the focus mechanism bushes. Nothing to do with the flange. If you were in the UK, I'd recommend Asahi Photo to have a look at it. They do not charge for a repair estimate but you would probably have to send the lens to them in London to have a look at. They are very good, quick (10 days), not too expensive and they can repair just about any Pentax lens or camera old or new.

stevebrot · 10-19-2014, 10:22 AM

Originally posted by TomGarn

But how to do it with a photo-lense ? Ist there a chance ?

There is no need for a non-cinema system. The equivalent operation for K-mount would be to adjust the lens infinity focus to agree with both the hard stop and the lens distance scale.

Steve

---------- Post added 10-19-14 at 10:24 AM ----------

Originally posted by kh1234567890

Mine is beginning to go that way. Apparently due to wear on the focus mechanism bushes.

That makes sense.

Steve

TomGarn · 10-20-2014, 08:34 AM

Anyway ... what we are talking about is quite the the same, isn't it ?
Flange correction is equal to adjusting that old case loosing true focus.
Anyone knows about "Doing it yourself" ?
I guess some optical instruments need to be aquired to turn and twist lenses and screw them up

kh1234567890 · 10-20-2014, 10:15 AM

It's your lens ,,,

10-19-2014, 09:47 AM	#1
TomGarn Veteran Member Join Date: Sep 2013 Location: Hamburg Posts: 339	Flange correction in old lenses I found out that sharpness gets lost when pulling back my zoom to wid angle. Lense: Pentax SMC A 35 - 105 / 3.5 A fine lense I use for video mostly - and with manual focus only of course. FLANGE must be the problem - more so because the zoom-ring moves very tense and also very close to the ring with f-stops - and very near the camera body. So also it happens again and again, that this small button used to fix the A-position gets unlocked then. The Pentax service in Hamburg refuses to look at it - maybe it's to old and to cheap for service ? And I know in broadcast-video-cameras the flange must be looked after each change of lense (for best) Anyone knows how to do it himself ? With video-cameras you do it with a SIEMENS-STAR graphic, comparing tele and wide-angle ... we have a special knob to twist and adjust... But how to do it with a photo-lense ? Ist there a chance ? Last edited by TomGarn; 10-20-2014 at 08:26 AM.

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10-19-2014, 10:18 AM	#2
kh1234567890 Veteran Member Join Date: Sep 2010 Location: Manchester, UK Photos: Gallery Posts: 2,653	Originally posted by TomGarn I found out that sharpness gets lost when pulling back my zoom to wid angle. Lense: Pentax SMC A 35 - 105 / 3.5 This a common problem with this lens. Mine is beginning to go that way. Apparently due to wear on the focus mechanism bushes. Nothing to do with the flange. If you were in the UK, I'd recommend Asahi Photo to have a look at it. They do not charge for a repair estimate but you would probably have to send the lens to them in London to have a look at. They are very good, quick (10 days), not too expensive and they can repair just about any Pentax lens or camera old or new.

10-19-2014, 10:22 AM	#3
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by TomGarn But how to do it with a photo-lense ? Ist there a chance ? There is no need for a non-cinema system. The equivalent operation for K-mount would be to adjust the lens infinity focus to agree with both the hard stop and the lens distance scale. Steve ---------- Post added 10-19-14 at 10:24 AM ---------- Originally posted by kh1234567890 Mine is beginning to go that way. Apparently due to wear on the focus mechanism bushes. That makes sense. Steve

10-20-2014, 08:34 AM	#4
TomGarn Veteran Member Join Date: Sep 2013 Location: Hamburg Posts: 339 Original Poster	Anyway ... what we are talking about is quite the the same, isn't it ? Flange correction is equal to adjusting that old case loosing true focus. Anyone knows about "Doing it yourself" ? I guess some optical instruments need to be aquired to turn and twist lenses and screw them up

10-20-2014, 10:15 AM	#5
kh1234567890 Veteran Member Join Date: Sep 2010 Location: Manchester, UK Photos: Gallery Posts: 2,653	It's your lens ,,,