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Old November 20th, 2005, 04:52 AM   #1
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New Letus35A problems. Suggestions?

I got my Letus35A on Wednesday after the Post Office took over a week to deliver Priority Mail. I'm not happy with them about that, especially since it means that sending my adapter back will take over two weeks to get it fixed. I am grasping at straws and know that I will probalby have to ship it back, but I figure that I should at least try to ask for help since I can't mail it until Monday.

I can not get my VX2000 to focus on the GG at any zoom, focus, or aperture setting. I have tested it extensively powered on and off and focus is not happening. The only way I got it to work is by loosening the mount and sliding the adapter forward, effectively lengthening the adapter. I don't know well enough how these adapters work to understand the relationship between all the lenses.

The VX2000 has no trouble focusing on objects near the lens. I removed the macro lens from the adapter and tested to see how close I could focus with it on the VX2000 and I could touch a q-tip to the lens and all it's fuzz was in focus. Somehow, when I put it back together, the achromat lens mounted in the tube changes all that. I don't understand how this is possible, so I am stumped.

Any ideas?

You have 36 hours to give a suggestion or you fail at this task!

Marcus
Marcus Marchesseault is offline   Reply With Quote
Old November 20th, 2005, 05:30 AM   #2
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Marcus,
I dont want to jump into Quyen's shoe's here, but i dont think he will mind me making a suggestion.

It might be that the VX2000 does not need an macro to focus on the 36x24mm fram area, since as you say the cam has no trouble focusing on near objects. Is this the case? If so, then it makes sense to shoot without the macro at all, lens glass is better.

Just a thought, Quyen?
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Wayne.
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Old November 20th, 2005, 05:58 AM   #3
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//

Marcus,

I have the pd150. It's similar to the vx2000.

I need every lens in the Letus.
I did some quick tests with just the gg.

http://www.lesoup.com/fileadmin/user...uence%204f.jpg
http://www.lesoup.com/fileadmin/user.../private/1.jpg
http://www.lesoup.com/fileadmin/user...ate/zonder.jpg

The first one just looks better because it is lit very uneven.

Conclusion so far: the first lens after the gg gets rid of the light fall off. It also creates the barrel distortion.

The macro makes you zoom in. It has pincushion distortion. This compensates for the barrel distortion, but not enough. Therefore the Letus ends up with slight over all barrel distortion.

As seen here: http://www.lesoup.com/fileadmin/user.../private/7.jpg Yes, I know it could be sharper.

So. It puzzles me a bit that you can't get it to work. I think I have the same lens system in my camera. But I hope I have helped a bit.

I must say that I do must zoom until the very edge to fill the frame. One nudge further and everything is fuzzy. But I really can't do it with just the gg, although I would very much like that, of course.
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Old November 20th, 2005, 07:05 AM   #4
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I didn't realize that the macro has pin-cushion distortion that helps correct the achromat barrel distortion. The design makes more sense now.

I know what you mean about the vx2000/pd150 and it's zoom focus. There is a point during zoom-out where focus abrubptly changes. I think there may be an aperture change at this point as well. I am not going up to that point with the Letus35A installed. I can zoom well into the GG frame without the focus changing. It is just soft-focus all the time, then it abrubptly changes to totally out of focus if I zoom really far.

I can only focus on the GG if I move the achromat/GG assembly farther away from the macro. Also, if I move the entire assembly away from the camera a bit it will focus. I am really stumped by this because I can hold the lens and GG alone the same distance away from the lens as the aluminum tube does and it will focus. The achromat/macro in place make focus not work within the tube's distance. I'm guessing that focus would work reasonably well if I put a clear filter on the camera before attaching the Letus35A, but I don't want to apply a workaround to a system that is already half the size of the camera itself and has plenty of mounts and connections already.

Speaking of mounts, the plastic lens mount is really loose and I don't see it holding up for long if I switch lenses frequently. If this link works, does anyone know where to get these nikon replacement body mounts? B&H is out of stock.

http://www.bhphotovideo.com/bnh/cont...goryNavigation

Thanks for the detailed tests and information.

Marcus
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Old November 20th, 2005, 07:17 AM   #5
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If you're really desperate...

http://www.thorlabs.com/NewGroupPage...&Visual_ID=879

I understand your feeling about adding even more stuff. But look at it the other way: the letus is relatively small. Also, I would certainly add a rod support.
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