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K-3 groundglass out of collimation?


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#1 Dennis Kisilyov

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Posted 26 January 2007 - 03:40 PM

I've finally completed and processed the K-3 test roll shot on 200T kodak film.
I printed the ISO-12233 chart and taped it to a wall. Using two M42 primes and varying f-stops.

I used the ground glass in the K-3 for focusing, and at low f-stop numbers I see that it's un-sharp.
While at f5.6 and f8 the footage is very very sharp.


Does anyone have advice? - Do you think I should troop to DuAll and have the thing collimated and give them
the primes and the Meteor, or should I just have low sharpness expectations for F1.4 F2.0 F2.5 etc..?

I'll try to post a few screen grabs.

P.S. The roll was processed and Tele-Cined at PostWorks NYC. They rock! They did such a good job!
The colorist even flipped the tungsten film where it was shot w/o a 85B in daylight.
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#2 Dennis Kisilyov

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Posted 26 January 2007 - 04:15 PM

Here are the screen grabs.


Chinon 50mm 1.7
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Vivitar 28mm 2.5
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Meteor 17-69 1.9 Zoom
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Pentacon 1.8 + 85A MC (at f2.4)
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Make note the 50mm F4 is actually F1.7 (error in sharpie)
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#3 Bernie O'Doherty

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Posted 26 January 2007 - 06:57 PM

Here are the screen grabs.
Chinon 50mm 1.7
Posted Image
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Vivitar 28mm 2.5
Posted Image
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Meteor 17-69 1.9 Zoom
Posted Image
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Pentacon 1.8 + 85A MC (at f2.4)
Posted Image

Make note the 50mm F4 is actually F1.7 (error in sharpie)



[Could be the groundglass position, or it could be that the lenses are out of collimation/calibration.
I find that more than 50% of cameras and lenses I service are off on flange focal depth and collimation/calibration. As you can see from your test, the real sharpness test comes when you're wide open on the lens. I really feel that the lenses are slightly off on calibration.
Cheers, Bernie
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#4 Charles MacDonald

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Posted 26 January 2007 - 08:18 PM

Does anyone have advice? - Do you think I should troop to DuAll and have the thing collimated and give them
the primes and the Meteor, or should I just have low sharpness expectations for F1.4 F2.0 F2.5 etc..?

1) Soft results at larger apatures may be that a lower depth of field is showing up a slight misallignment of the focus screen. It is not cheep to have the setup calibrated, but if it is adjusted you will get the maximum quality you can get.
2) chinon is not a famous brand for lenses. I would not be surprised if a takumar was not sharper..
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#5 Dennis Kisilyov

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Posted 26 January 2007 - 10:43 PM

1) Soft results at larger apatures may be that a lower depth of field is showing up a slight misallignment of the focus screen. It is not cheep to have the setup calibrated, but if it is adjusted you will get the maximum quality you can get.


I am leaning towards that, true a K3 is not an arri, but it's not supposed to overshoot the focus that much.
Plus 16mm is a bigger DOF than 35, so minor focusing problems should not show up as much as they would on a 35mm SLR the same lenses attach to...

2) chinon is not a famous brand for lenses. I would not be surprised if a takumar was not sharper..


100% True, I have a large set to M42 lenses, Oddly I have about 5 1.4 SMC/Super Takumars on the way.
Though I though the particular Chinon I have is a product of the Tomioka lens factory which is supposed to be an *OK* lens.

There are always the new ZS 2006 lenses from Zeiss.

Edited by Dennis Kisilyov, 26 January 2007 - 10:44 PM.

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