Revisiting the Optex PL-to-XL Mount Adapter at DVinfo.net

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Old August 29th, 2002, 11:15 PM   #1
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Revisiting the Optex PL-to-XL Mount Adapter

I have been wondering:

Since the physical frame size of 35mm film is much bigger than the 1/3" CCD of the XL1, one would not get an exact reproduction when using this adapter; the image size formed by the take-up lens exceeds the area covered by the CCD.

Which also means that the flange focal length has overshot the focal plane (i.e., the CCD) and is converging to a point somewhere behind the CCD.

Would it help if we extend this flange focal length by moving the take-up lens further forth of the CCD (and the camera body) so that the focal point can fall onto the focal plane?

Correct me if I'm wrong, but if we try and preserve the flange focal length of the PL mount (2.047 inches, 51.9938mm), wouldn't we essentially have a 35mm image hitting the CCD? However, I suspect there will be heavy vignetting at wide open.

I have absolutely no idea if I'm making sense or not. Any thoughts or opinions to share?


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Old August 31st, 2002, 08:03 AM   #2
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I believe the OpTex adapter uses a relay lens. The relay lens compensates for the flange focal length differences. The use of a relay lens is the inexpensive way to adapt various lens mounts to the XL. The expensive way is with the PS Technik adapter. If you use the search for Technik you'll find several threads discussing the merits of it.

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Old August 31st, 2002, 11:54 AM   #3
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The optex adapter is not optical and in turn does not scale the image plane down to the size of the ccd. Hence the telephoto effect.

The mini35 from P+S Technik uses a ground glass to relay prism than an optical iris to transfer and scale the image to the ccd. This gives you the same focal length as rated by the lens you are using.

I believe if you move the lens further from the ccd you'll only make the image even larger than the ccd. Pretty much the exact affects of a range extender.
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Old September 1st, 2002, 09:39 AM   #4
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Justin,

I suppose you're right. We'd need a glass of some sort in there to collimate the entire image formed by the take-up lens onto the CCD, which is what the Mini 35 is all about.

Oh well, I was just toying with the thoughts of having alternatives to the Mini 35. So much for wishful thinking. =P

Then again, has anyone tried this adapter? I remember Charles Papert saying he wanted to try it out. I wonder if he (or anyone else) already had.
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