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Old January 10th, 2006, 01:37 PM   #16
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I use the VX2000 for which the Letus35 was developed. I had to send mine back initially due to inability to focus on the ground glass. It seems that the tube was to short for my camera. Actually, I have the Letus35A and there may have been a problem introduced when Quyen changed achromats. That is my guess. I'm sure he has that issue solved by now. Regardless, you can experiment with the Letus by unscrewing it and holding it different distances from the camera. To check backfocus, move the camera lens away from the Letus35 slightly. My backfocus was off by about 1.5mm so I heated the hot glue on the sticks that hold the ground glass and repositioned the element.
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Old January 13th, 2006, 05:36 AM   #17
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I made some more intensive tests and I found out that the 58mm thread simply won't work with the FX1. I used a step down ring and it fits but you have to zoom in so much into it that you simply cannot get the right image. Before I start shooting I tried findind the sharp spot without zooming in and with the motor off and it is simply impossible. I set the 55mm lens to infinite and use the FX1s' enhanced focus to manualy look for it but it is never fully on focus. When I turn the focus ring a little bit away from infinite, I achive a fully focussed image, but as soon as I zoom in to fill the entire frame, it reaches a point where the image doesn't seem to be able to fully achive full focus, no mater the setting. So, I decided to test the image I shot without zooming in (where I can see most of the interior of the adapter) just to see if it could be used if I croped it from HD to SD using only the center of the image (which would be useless because I want to be able to have the final results in HD too). The image contains a lot of grain even with a lot of light. I think that maybe the 72mm thread letus35A MIGHT work for the FX1 IF it alows you to frame the image properly without having to zoom in so excessively...but then again...I tried the letus35 with a 58mm thread cam (GL2) where I didn't have to zoom in as much and the image was still way too videosish and soft. I would love to hear from some Letus35A owner who has a FX1...even more I would love to see some footage.
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Old January 13th, 2006, 07:28 AM   #18
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Quote:
Originally Posted by Marcus Marchesseault
My backfocus was off by about 1.5mm so I heated the hot glue on the sticks that hold the ground glass and repositioned the element.
Marcus, this will throw off your depth of focus drastically. Now all the readings on your lens will be inaccurate and the infinity focus will, well, no longer focus to infinity. Be sure to keep the distance from the SLR lens and the focusing element the same as Quyen built it.
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Old January 13th, 2006, 07:42 AM   #19
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Ben, the way I discovered that I had a backfocus issue was that my ranges were all wrong and infinity would not focus. In my case, it was not built with the correct range. All of my lenses were off and now they all work and have proper focus in relation to their markings.
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Old January 13th, 2006, 08:11 AM   #20
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Quote:
Originally Posted by Marcus Marchesseault
Ben, the way I discovered that I had a backfocus issue was that my ranges were all wrong and infinity would not focus. In my case, it was not built with the correct range. All of my lenses were off and now they all work and have proper focus in relation to their markings.
I think this might be the case with me. I simply cannot focus when the lens is at infinity (ANY lens).
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Old January 13th, 2006, 10:14 AM   #21
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If the backfocus is out, the image will be inferior with the wide lenses, ie., 28mm, 24mm. I have a 12mm - 24mm digital Nikon which was hopeless, but came in to an acceptable level when I took meticulous trouble to get the back focus right.

Even if can can focus past inifinity with numbers mismatching, the result to infinity still will not as sharp as when the lens os correctly positioned for backfocus.

That's what I have found with my setup anyway. It could be an illusion or delusion on my part, but that is a I saw it.

There is another issue - that of the groundglass being at true right angle to the lens axis, both laterally and vertically and then the camcorder lens axis also being central and parallel to (non-erecting) or parallel to (prism erecting) the SLR lens axis, ie., also at a true right angle to the groundglass.

This is a very real issue for builders of the CD-R spinner versions. For any, it is desirable for the backfocus and angular adjustments to be built in. If we want the results that are obtained with film cameras, then the same meticulous trouble has to be taken to set up the optics.
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