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Alternative Imaging Methods
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Old October 16th, 2006, 09:22 AM   #16
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Join Date: Dec 2003
Posts: 4,299

Furthur to my comments on the cardboard washers, I have since found these tend to ride up over the first internal ridge and are less than satisfactory.

I have changed my temporary spacing arrangement to a 5mm sleeve cut from PVC pipe which has a 1.5mm wall thickness. I had to cut a small piece out of the pipe and close the ends together to make it fit in the space like an automotive piston ring.

The depth of this sleeve needs to be 6mm. To be safe, I have cut the sleeve to a 5mm depth and used cardboard washers between the sleeve and the rearmost internal face where the glass panel rests to make up to 6mm.

The new spacer arrangement goes between the rear of the mount and the rearmost internal face of the adaptor's mount hole. It ignores the small ridge which is the step in from the smooth machined area the mount rests in and the rough non-reflective finish between the mount and the glass panel.

I have yet to do a fine adjustment to this fixed arrangement as I don't have the XL1 with the Letus to test it.

If you drill or mill flat bottomed holes across the Canon portion of the mount, down to the bottom of the groove, you will have to replace the thumbscrew with a longer screw as it will not be long enough to bind on the floor of the hole.

Once the two extra screws at 120 degree radius centres are installed, the whole thing becomes quite stable.

To get a square mark out and cut on the plastic pipe, take a piece of printer paper. Wrap this around the pipe and pull it up tight and adjust it until the wrap is both tight and the paper edge square. You have now got a straight edge to mark to.

A permanent felt tipped marker is the best for this. Make a quick line around over both the plastic and paper. Check that the ink goes up to the paper, then pull the paper off before the ink runs under. When the second mark and cut is made it is important that this be perfectly parallel to the first cut and the depth thickness is the same all the way around.

Sorry to be wrecking your confidence with all this stuff. The end result is worth the effort.
Bob Hart is offline   Reply With Quote
Old October 18th, 2006, 09:42 PM   #17
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Join Date: Sep 2005
Location: NYC, weeee.
Posts: 417
Bob, you have a ton of info here.
I had back focus problems at first with my 35A but found that if I pushed the lens mount as far in as it would go and really hold it there while I tightened it down, it fixed the problem. (i'm using canon lens's). I have 4 lens's and they all backfocus fine. The better faster lens's (more expensive) seem to have the best colour and focus, 50mm ssc 1.4 and 100mm 2.0. the 24mm 2.0 vivitar and the 70-200mm vivitar zoom don't look as good, but I was expecting that from the zoom lens. The colour of the vivitar lens's look a little washed out and the sharpness isn't as good.

Finding the right combination of camcorder fstop and lens fstop was critical. each lens has a sweet spot and finding that was a chore. remember what each one is, is even more of a chore. But in general, I find that leaving the canon len's wide open or slightly closed and closing down the camcorder iris gave me the cleanest picture. I also took off all of my uv filters and removed all critical glass, gave me the best image. Now the issue is dust. uuuhhg. I clean the freakin thing all the time. I have a whole procedure of panning the camera around in bright light to find the little dust demons.
Michael Fossenkemper is offline   Reply

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