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Mark Beadle
Mark240590
United Kingdom
8 Posts |
 Posted - Jun 03 2020 : 03:19:02 AM
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Hey all,
Just taken delivery of this camera, don’t have the original lens but have a Rikenon 50mm f2 however it doesn’t seem to be focusing correctly. I wonder if the Flange focal length is the same as Pentax K lenses ? |
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Scordisk
3 Posts |
Posted - Jun 03 2020 : 04:20:55 AM
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As a first check:
do examine the position of the mirror, its angle. Don't change it.
But, make a test with a film: on a tripod or on a firm place under the camera, measure several distances from the film plane with a manual meter - 1,5 - 2 - 2,5 - 3 - 5m - and always use the signs on the lens for the first shot, for the 2nd shot use what the viewfinder gives you.
I.E: on each distance, make one shot with manual metering and use signs on the lens barrel, then the 2nd shot use the pentaprism focusing.
Use f/2 or the largest opening.
Then you'll be able to evaluate whether the body (or mirror) is calibrated badly, or the lens.
Afterwards, you can decide the following:
IF this body still has a small black screw, like on Zenits M42, on the side or little bit under the mirror on one side. This screw serves for calibration of the focus in the camera, and changes angle of the mirror. Do please lubricate it before, with WD-40 or similar lubing liquid.
The conclusion: for example, if you manually measure 2M with a meter, you have to put 2M on the lens, and then intervene on the tiny black screw in order to bring it into focus in the viewfinder. Of course, the infinity as a parametre can be of help, but focusing on short distances is much more important.
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Edited by - Scordisk on Jun 03 2020 04:28:59 AM |
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Mark Beadle
Mark240590
United Kingdom
8 Posts |
Posted - Jun 08 2020 : 04:37:25 AM
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| Thanks for this. Great walkthrough on testing ! |
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Scordisk
3 Posts |
Posted - Jun 16 2020 : 04:53:45 AM
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The above method(s) apply when we consider plausible the focus brought by a lens onto film surface. I.e. that infinity on the lens results in infinity sharp focus on the film plane.
But it is quite difficult to discern focus results on the film plane, with amateur methods (darkening a room, placing a matt screen over the film plane or placing a semi-transparent foil, placing a lamp at about 1,5-2M in front of the lens, a tiny object to focus on, etc.) The 24x36 format is so small.
The corrections of this type on a common SLR do not exist and are irrelevant, unless one uses washers or thin cardboard foils, for calibration under the body ring, Pentax K in this case. |
Edited by - Scordisk on Jun 16 2020 05:28:08 AM |
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Almaz 103 Pentax K mount
