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Old June 27th, 2004, 03:41 PM   #946
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GG Minolta Type G, Maxxum: I found a GG with the same smal grain, but without "circles" and without marks. Read this:

Alex, thanks, but it is so: I have tested this GG type last year. And it is, like i said it before, this GG is not grainless. Okay, it is one of the best, and you must exact focus on it to see the grain. But than most (PAL version) cams see the grain. There are also some circles on it (not only one, like you say) but this is because this GG has a fresnel lens inside.

My company work with 35mm solutions since many years, so we have tested every GG we found. For my requirements this Minolta GG with this grain was too bad. Maybe it work with NTSC. But i can say we have a GG with exact the same grain like this Minolta Type G. The different is, it is without fresnel(=circles) and without marks.
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Old June 27th, 2004, 06:39 PM   #947
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So, what are the results?
What GG is the correct one?
Do they have Fresnell or Microlens? They are not the same.
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Old June 28th, 2004, 04:16 AM   #948
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Juan, the Minota GG Type G is a sandwich Type: fresnel + GG + (one-side-flat)lens. The fresnel lens kill the hot spot, but produce also the circles. And thatīs why it in not unusable.
If the GG itself came with microlens or not, i dont know.

We use a optical bank to test groundglasses. A (still photo) pojektor with a high def testpicture on one side, the GG in the middle, and a microscope on the other side. For a good GG, there are 4 importantly points: low light loss, small grid, hight scharpness, and very even (no clouds or shadows).
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Old June 28th, 2004, 05:14 AM   #949
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So you still recommend the Wax/Parafin compound way?
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Old July 4th, 2004, 09:43 AM   #950
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Brett.

Is your email address as posted still current. I have a comparison test pattern split-image .jpg of the Agus35 (5 micron oharadisk)into PD150 plus a .jpg of the 5 micron machine-finished oharadisk while stationary which might offer some comparison with the other hand-finished 5 micron Aldu35 versions. I'm still using the SW5042 lens set which is inferior to the setups others here are using.

ADDENDUM TO THIS POST:

The comparison image is at www.dvinfo.net/media/hart and titled "oharcomp.jpg" There is also another image with the 5 micron AO dressed disk stationary, ie., fixed groundglass titled "oharatp1.jpg".
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Old July 7th, 2004, 04:52 AM   #951
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New images

I finally got to test my adapter in the field, so to speak, as I helped a friend finish his installation of a spiral staircase. I used a bosscreen in my adapter that day. It seems to be the best solution so far, but I have a friend who works with glass who will see about grinding a finer grain in the 5 micron GG I have.

The images were captured directly from tape to memory stick on my video deck (so they were compressed), with a little gamma correction done in Photoshop.

I am seeing some color bleeding around the edges of bright objects (purple especially), but I'm not entirely sure what causes it. I am working to take care of the light leaks (there are some pretty big holes) and figuring out a design that will allow me to remove some of the glass elements from the optical path.

I will post a short video clip to accompany the shots soon.

http://www.edwardflinch.com/images/DSC00003.JPG
http://www.edwardflinch.com/images/DSC00004.JPG
http://www.edwardflinch.com/images/DSC00007.JPG
http://www.edwardflinch.com/images/DSC00011.JPG
http://www.edwardflinch.com/images/DSC00016.JPG
http://www.edwardflinch.com/images/DSC00017.JPG
http://www.edwardflinch.com/images/DSC00018.JPG
http://www.edwardflinch.com/images/DSC00019.JPG
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Old July 7th, 2004, 10:21 AM   #952
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Michael,

The images look really good.

The purple fringing may have less to do with the adapter's optics than with the DV imaging process itself. I may not be remembering this correctly; but I believe DV will sample luminance, red/cyan and blue/yellow and then calculate the values for green/magenta. It also samples the luminance spatially more frequently than the two colors. So when the luminance shifts markedly from one line to the next, and it's still pretending the sampled colors from the prior sampled line line are unchanged, the green/magenta value ends up being inaccurate. This leads to the fringing.

So you may be getting that fringing even without the adapter.
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Old July 7th, 2004, 04:28 PM   #953
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<<<-- Originally posted by Kaushik Shridharani : Michael,

The images look really good.

The purple fringing may have less to do with the adapter's optics than with the DV imaging process itself. I may not be remembering this correctly; but I believe DV will sample luminance, red/cyan and blue/yellow and then calculate the values for green/magenta. It also samples the luminance spatially more frequently than the two colors. So when the luminance shifts markedly from one line to the next, and it's still pretending the sampled colors from the prior sampled line line are unchanged, the green/magenta value ends up being inaccurate. This leads to the fringing.

So you may be getting that fringing even without the adapter. -->>>

I sure hope not, but I don't think that's the case at all. I've had the camera for over 2 years and I've never noticed fringing of any colors. It's also a GL2, which I believe samples the green CCD more than the red and blue CCDs.
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Old July 7th, 2004, 07:15 PM   #954
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Michael very good images. What lens are you using? And, can you list the steps of how your adapter is put together. Thanks.
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Old July 7th, 2004, 08:11 PM   #955
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9 out of 10 times color bleed problems like the ones in your pictures are due to "chroma aberation".

Your using some form of a diopter (ie. plano convex lens, close up lens, etc.) arent you. Most likely that diopter is a inexpensive/single element lens. These diopters will have color bleeding problems.

To varify if this is the problem look at your footage again. Watch the section in the video that you noticed the problem. When the camera pans over and the object moves from the corner of the frame to the center - does it still have the color bleeding problem. In other words chroma aberration is only noticeable at the edge of the frame.

To fix it get a two element (or more) diopter (also known as a achromatic diopter).

As always for more info on this subject and many others do a search on the key words, "Achromat", "aberation" etc because this has already been explained in detail.

-Brett Erskine
www.CinematographerReels.com
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Old July 7th, 2004, 09:19 PM   #956
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Ernest:
The lens I'm using is a Nikon 50mm 1.4. You can see the adapter on this page:
http://www.edwardflinch.com/images/mini35.htm

Brett:
The dipoter I'm using is a +7 Century Optics Acromatic Diopter. A $200 piece of glass, it's the most expensive part of the setup, so I certainly hope it's not the source of the trouble.

I believe that the problem lies in the internal reflections within the setup. On some occasions I noticed a ghosting effect because of it. I will do more tests.
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Old July 7th, 2004, 09:53 PM   #957
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Maybe it's the condenser lens doing the chromatic aberrations. I would paint all the non-glass in your setup matte black to minimize flare.
There are ways to correct some chromatic aberrations in software. Panavision does this.
-Les
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Old July 8th, 2004, 04:16 PM   #958
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Les-
Interesting. I didnt know Panavision did that. Send me a link if you have it.

Mike-
Yeah that Century its great glass. Im with you. I highly doubt its causing the problem. I agree with everything Les said. Check it out. Pull the condenser out of the system and try it again. Also you can hand hold the condenser over say a newspaper and look for chroma aberation at the edge of the condenser.

Brett Erskine
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Old July 9th, 2004, 12:57 AM   #959
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The mentioned it when they talked about the anamorphic lens, if I remember correctly. It may be just a channel resize, or maybe a bit more fancy, like an affine warp of selected chroma ranges.
Could be done as a post process.
-Les
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Old July 10th, 2004, 12:57 AM   #960
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that is very silly to put a processor to correct thing after you make them bad using poor elements.
At surplusshed you will find a 52mm achromat for 5$.
it works very well for my vx2000 and you can even use two of them (one for the condenser and one for the macro)
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