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Old July 26th, 2005, 09:54 AM   #1
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Condensers wow!

Well, I think I found my condenser. Holding it up to the GG, very close to it, brightened up the image considerably, without distortion. I am still trying what Oscar did, put another condenser close to the lens to get a more even spread of light coming out of the lens first, but it really seems to distort everything when I try it, the focal length goes out etc. Hey Oscar, how did you combat the focal length problem with the condenser next to the lens??
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Old July 26th, 2005, 10:02 AM   #2
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What condenser are you using? I'm curious since I'm ordering one either today or tomorrow. Most importantly...what's the focal length? (I'm thinking of buying about 100mm)
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Old July 26th, 2005, 10:07 AM   #3
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Quote:
Originally Posted by Mandy Leo
Well, I think I found my condenser.
Congrats. Cant wait for result... Btw - how was you eBay bids ?
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Old July 26th, 2005, 10:20 AM   #4
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Leo, I put the condensers together with the GG. Like this: http://s01.picshome.com/be6/c1.jpg
I put the GG on the focal plane, I don't think it changes with the condenser. The patent of the MovieTube shows the same setup: http://v3.espacenet.com/textdoc?DB=E...DE10240076&F=0
I wonder what that 'field lens (5)' is about.
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Old July 26th, 2005, 10:51 AM   #5
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Awesome, thanks for the link. I am going to try that now. I was putting it close to the lens instead of the GG. Also going to try the static route with that in mind as well.

Also from the link, what does a field lens do? Any ideas?
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Old July 26th, 2005, 11:01 AM   #6
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I think we need Aaron Shaw again. The only thing I can think about is that it magnifies the image.
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Old July 26th, 2005, 11:24 AM   #7
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According to their setup, they use 2 condensers totaled +9, I think 1 is about 250mm (+4) and 1 is 200mm (+5) focal length. They are not enough to solve the hotspot problem. I guess the field lens 5 is to solve the hotspot.

Quyen
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Old July 26th, 2005, 11:59 AM   #8
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I was outbid on all accounts of the ebay for focus screens. They really went up in price on the last hour of bidding!
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Old July 26th, 2005, 12:02 PM   #9
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So 100mm would be about +10 then? I think that might work.
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Old July 26th, 2005, 12:41 PM   #10
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100mm between the lens and gg is too much. If you use fresnel, it should be OK. thick glass next to gg will push the focusing image a little further and the edge will be out of focus. I think 250mm will be the best choice there. It will do some damage but hard to see.

Quyen
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Old July 26th, 2005, 12:57 PM   #11
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I did some research on the field lens, and it looks like a condenser but thicker. If that is the case, I have one sitting around here and did a test - but you know what, the condenser I have sitting in front of the GG right now is doing such a great job, I don't think I am going to need it. I am stepping down on my GG to my own homemade one with fine sandpaper. I coudn't use it before because of the hotspot, but the condenser seems to have evened it out completely, which is cool - but still more tests are needed.
Better than all of this, I don't need the achromat anymore, but the condenser spreads out the light enough that I don't get vignetting anymore. I am still trying to place another condenser on the other side of the GG

(LENS (| GG |) DV) (thanks Oscar!)

but the extra one I have seems to make it more blurry around the edges. So far, I think I might be able to get away with the one condenser. After I run some tests, I am going to build the full DOF machine and get rid of the prototype - after that, it is wax and static! (god, how many times have I said that!)
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Old July 26th, 2005, 03:19 PM   #12
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Well, testing brings out the worst in us, doesn't it?
I found that without the achromat, I am getting barrel distortion from the condenser - just at the edges. I wouldn't have noticed it but for the window pane being curved! Oh well, back to the drawing board. I am going to throw a achromat in the mix and see what happens.
Also, I have noticed that stepping down on both my DV and the lenses seems to eliminate the hotspot, but then it doesn't let as much light in either, leading to a darker scene.

I think I am going to order a large diameter Condenser as well. This one is nice, but not large enough, so I am still getting very minimal vignetting with it.

Also, it is interesting that on the micro35 board, some guy has put up footage of his micro35 adapter and you can really see the hotspot on it. He has a bunch of .tif of the footage. Overall it looks good, but at least I don't have to wonder anymore if anybody else was experiencing it.

Last edited by Leo Mandy; July 26th, 2005 at 05:54 PM.
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Old July 27th, 2005, 09:34 AM   #13
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Mandy -- what kind of condesnor do you have?
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Old July 27th, 2005, 10:28 AM   #14
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Type? I am not sure. I got it from a film strip projector - it is clear, |) about 45mm diameter and 10mm thick. It really lights up the GG when pressed close to it, but again, it is not big enough (I am guessing) because without an achromat, I sometimes see the sides of it and some minor vignetting.
On another note, it is interesting what the viewfinder sees and what actually is happening once you dump it to the computer. Vignetting that I didn't see before is actually present.
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Old July 27th, 2005, 05:26 PM   #15
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With a DCX lens between the GG and the 35mm, wouldn't there be alot of barrelling and distortion?
I know that with the m35 there is one, I am just wondering the purpose? With Oscar and others, they are putting the (| against the GG, isn't a DCX lens a double convex?

Last edited by Leo Mandy; July 27th, 2005 at 05:56 PM.
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