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Old January 15th, 2006, 09:58 PM   #31
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Seems that several of you are already looking into the thin-film polymer material (sounds better than sandwich bag).

Here are a few guidelines:

-White bags absorb too much light in my opinion. Check my test earlier on this thread, you can see that the screen is pretty much invisible when right against a printed page.

-In general the thinner the material the less light loss you will get. Therefore, a coffe can lid or acrylic is too thick for our purposes. On the other hand, the plastic used to keep 35mm film negatives may just be a good one to try.

-Not all noisy, non-shiny, translucent grocery bags will work. Do the diffussion test as in my previous post. Be also prepared to find several different grain grades.

-You are not looking for a frosted type material, this one has absolutely no texture, and the "grain" is very difficult to see unless you look at your finger through the screen while pointing the material towards some ambient light source.

-3M magic/invisible tape is good but has too much striation (length wise texture lines). It also suffers from light loss because of it being too thick. You can remove the glue from it with some solvent, but then what's the point of using it? If someone can find magic tape at least 4.5 cm wide it may just work (there are more manufacturers other than 3M).

I am thinking about coming up with a way to quantify the grain grade of different materials so that we can compare them more easily. A lightloss test would be quite useful.
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Old January 15th, 2006, 10:05 PM   #32
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Quote:
Originally Posted by Marco Polimeni
Alain, please can you say how are you going to fix the adapter to the camcorder ?
I already have it fixed via plywood. The adapter is screwed in and I made a hole to screw the camera via it's tripod screw mount.

As I said in the first post, it is bulky (not as bulky as the Halina viewer that was posted later, mine is much smaller). So I am trying to decide on my optical setup so I can buy some lenses and make a small one.
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Old January 16th, 2006, 07:05 AM   #33
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Alain,

I would like to hear more about this colloidal liquid diffuser idea, sounds very interesting, would love to know more!
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Old January 16th, 2006, 10:21 AM   #34
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Yea Im sorry, It wouldnt upload, I have too many projects on my server. My demo is almost 100mb, and my films are pretty big too. Im gonna make a smaller verion and post it soon.
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Old January 16th, 2006, 10:40 AM   #35
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Quote:
Originally Posted by Bryan Ramirez
the footage I was talking about is at:

http://irezfilms.8m.com/1%20Mbps%20CableLg_Prog001.mov

the plastic bag was used inside, and the coffe can lid was used outside.
here is the new link:

http://irezfilms.8m.com/irez35.mov
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Old January 16th, 2006, 11:14 AM   #36
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Neat stuff. Way to be innovative! I don't know whether it's the compression, the prime lens, the "GG," or the camcorder, but the footage has a nostalgic feel to it.

Keep it up!
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Old January 16th, 2006, 04:12 PM   #37
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Thanks Bill, I think it's actually a mixture of it all. I used a canon Xl1s at 1/75 shutter in frame mode, a Nikon 55mm 2.2, and a home made adapter. and the outside footage was treated with magic bullet. The Plastic Bag trick really blew my mind. All this time I've been trying to think of cool ways to make ground glass, when it was just bundles under my sink.
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Old January 17th, 2006, 11:04 AM   #38
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VIBRATOR

I am not quite sure how to use a vibrator and avoid the screen moving from the focus plane. I have never heard of a surface mount vibrator, the ones I have seen are cylindrical shape micromotors.

Since the vibrator has a rotating weight, its axis would have to be placed perpendicular to the projection screen such that the oscillatory movement of the motor is in the same plane as the screen. But that makes for an awkward placement. If anyone has some diagrams, I would be very grateful.


LIQUID COLLOID

Wayne, I am not sure what more information you want about colloidal suspensions. Basically these are a type of solution of a given substance in a liquid, such that the substance is dissolved down to mollecular level particles which will repell each other and therefore will never settle to the bottom and remain evenly distributed in the liquid.

Milk is a colloid, so is butter, and ink. The trick is to find the right substance. I am also concerned with the Tyndall effect where light of different wavelengths is scattered differently in a colloid, but our screen is so thin that it may not have any problems of this kind.

The idea would be to take two sheets of glass, space them very thinly (just as with wax adapters) and feed in the liquid colloid into the capillar spacing. Of course the glass container needs to be sealed on the sides.

As I said I have not experimented with this but it sounds good in theory.
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Old January 17th, 2006, 11:08 AM   #39
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Alain,

Thanks sounds very interesting!

Here is a link to Quyen Le's tutorial on a vibrating setup: http://www.dvinfo.net/conf/showthrea...heap+vibrating

Maybe of help...
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Old January 17th, 2006, 11:36 PM   #40
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I had a go at a whole bunch of different household products between clear microscope slides. - Nice images but the groundglass texture almost immediately began to grow clear spots which became larger and larger.

According to our local pharmacist, the squeezing of emulsions between two close surfaces causes the water and oils to separate, a process called "cracking".

If somebody arrives at a solution it will be a good one as the image was grain-free for several cosmetic products for a second or two.

I gave up on it early in the peace and went for moving glass.
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Old January 18th, 2006, 11:05 AM   #41
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Wayne, thank you. It sounds like I was right about the alignment of the vibrator unit. All the images on that thread are dead though, so I can only try to make some guesses from the text.

That being said, I did a simple vibration test yesterday and it works nicely. I used soft foam to attach the base of the vibrating plate to the bottom of the adapter and it worked fine. I did not use the protruding arm concept that was discussed in the thread, but may try it later.

Bob, if I understand what you are describing correctly I think I know what the problems might be:

-It is not the same thing to press a liquid between two sheets of glass than to have a fixed cavity. When you press a liquid between the glass sheets, the liquid will spread but when you release the pressure it will naturally contract due to the lack of pressure and form the clear spots you describe (if I understood you correctly).

-The liquid must be contained to avoid spreading.

So if you make a cavity of fixed volume and seal the liquid inside, I don't think you will see any of the "cracking" you describe. Just because the liquid has no place to go.

I can imagine a few ways to construct such a cavity but will post once I have actually tried them :)
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Old January 18th, 2006, 12:28 PM   #42
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Here are some questions for you who are more experienced with working with lenses...

The suggested setup on the threads I have read is to place a PCX lens right next to the screen to serve as a condenser, and then another lens to be used as a magnifier (macro). An achromat is suggested.

Nevertheless, the setup I currently have from the slide viewer seems to work well.

http://mentemagica.com/35mmAdapter/Adapter1.jpg
http://mentemagica.com/35mmAdapter/AdapterTop1.jpg

First is the Nikon lens, then the screen, then, a couple of inches away is a PCX, and a couple more inches away a second PCX (the large one on the black plastic area that is tilted back). The screen I am using is about 5 x 4 cm and holds the whole Nikon lens image. After the first PCX, the image is about 6cm wide, still, I cannot get my GL2 to focus even on an image this large. So the second PCX magnifies it even further so I can focus.

From this I am assuming that no matter what marvelous screen I use, I will always need a magnifier (macro) lens.

With the first PCX a few inches away from the screen I get an evenly lit image, but I noticed something, if I move the camcorder closer to the viewer (closer to the second pcx), the image gets darker and I start getting vignetting.

http://mentemagica.com/35mmAdapter/FrameClose1.jpg

If I move the camcorder away, then the image gets lit better and the vignetting vanishes.

http://mentemagica.com/35mmAdapter/FrameAway1.jpg

The problem is that this makes my setup quite long.

(Note: These images are taken manually with a digital cam, not the GL2)

So my first question is: Should I adopt a different setup? Do you think I will get better results?

Second question: I want to buy better optics, should I get the highest magnification (smallest focal length) to reduce the length of the adapter or will that increase the aberration problems? Also, what about using an aspherical lens as a condenser? Will that work fine? (as I understand an aspherical will have less aberration problems).
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Old January 18th, 2006, 01:06 PM   #43
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Hi,
Regarding the vignetting, the behavior of moving the cam closer and further from the PCX is normal as there is a perspective shift while you do this. The bigger the camcorder lens the closer you can get with the same 'level' of vignetting.

To get your adapter shorter while keeping the image evenly lit, you will need a shorter focal length PCX (a little hard since you probably dont know the FL of the PCX in the slide viewer). Im guessing an 80 - 100mm FL PCX lens will serve you well with a GL2. Note that the shorter the FL of the PCX, the more chance of chomatic aberation and soft edge focus.

For the macro lens, try and find an achromatic lens for best quality
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Old January 19th, 2006, 12:50 PM   #44
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Quote:
Originally Posted by Wayne Kinney
Hi,
To get your adapter shorter while keeping the image evenly lit, you will need a shorter focal length PCX (a little hard since you probably dont know the FL of the PCX in the slide viewer). Im guessing an 80 - 100mm FL PCX lens will serve you well with a GL2. Note that the shorter the FL of the PCX, the more chance of chomatic aberation and soft edge focus.

For the macro lens, try and find an achromatic lens for best quality
The first PCX has a focal length of about 100mm from my tests (this is 3.5x magnification). So I think I may need something shorter. I think I will try one of the Optosigma aspherical lenses as condenser (they have one with about 7.5x magnification).

The lenses from my slide viewer are suitable for testing but I want something better. Most of my light loss comes from them, they are very thick and the material is plain glass so they even look greenish when I put them on top of a white paper. I can't wait to test my screen with some more luminous lenses.

Another thing, when I pull the camcorder away from the second lens, the vignetting disappears but the more I pull back the more chromatic aberration I get. So it seems there is a trade off:

Longer adapter = No vigneting + some aberration
Shorter adapter = Some vignetting + no aberration

Even fixing the aberration through the use of an achromatic pair or triplet, will not solve the vignetting issue. So the first lens (the condenser) seems to be of extreme importance.
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Old January 20th, 2006, 08:49 AM   #45
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i tried the bag idea last nite. Its the plastic see thru bags for vegetables not the white plastic right? anyways.. that stuff had almost no light loss compared to prior materials ive tried. my kitchen at nite was amazing looking

for a liquid.. what about clear fingernail polish? i havent tried it.. because i dont have any...
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