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10-29-2009, 05:26 PM   #16
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Now we just need to figure out how to get SDM drive motors into our homemade lenses. I think my first project will be to convert an old Mamiya 50mm f2 into a soft focus left (remove all elements except the front). I'll let you know how that goes.

11-05-2009, 06:28 PM   #17
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Polaroid Copal Oscilloscope Lens on K100D Super

This is GREAT - it's LBA without the "B" - ha, ha!

Thanks to Nick C for the inspiration, I decided to pursue a free lens...

I found a very old Polaroid oscilloscope camera lens in my junk box,
and decided to see if I could mount it on my K100D Super
and use it to take pictures.

It is a Japanese Tominon in a Polaroid Copal shutter, 127mm f4.7,
5-inch focal length, shutter speeds ranging from 1/125 second to
T setting which keeps shutter open. The aperture and
shutter work perfectly, and the glass is in excellent condition.

I found that I could mount the lens on the K-mount base of
my macro extension tube set, then could mount the K-mount
base with lens on my macro extension bellows. The bellows
easily focus the lens at 5 inches for a good infinity focus, and
the bellows racks out several inches to achieve focus as close
as a few inches for extreme macro photography.

Here are a few sample pictures taken with the lens shutter
kept open with the "T" setting and focusing by adjusting
the bellows. Various f stops were used to test the sharpness
of the lens wide open as compared to stopped down a few
stops. The Pentax K100D Super body was used as normal
for manual lenses to meter in Av mode and take the exposure.

Lens wide open (f4.7)

Lens stopped down (f11)

An infinity-focus test with lens at f11

A macro with the lens racked out

Taking a picture into the light, I don't see much sign of flare. It seems surprisingly immune, and appears to have some coating on the lens.

This was fun - maybe not all that useful, but fun!

11-06-2009, 04:41 PM   #18
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I've always been interested in doing stuff like this, but I'm not very keen on how to go about it. I found what I believe is an englarging lens, 500mm f/5 with two parts to the lens, that I'd like to turn into something usable. Can anyone give any advice?

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