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Old August 9th, 2006, 05:47 PM   #1
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Gound Glass sustitute Idea

Any "adaptor makers" out there ever consider a clear-like latex rubber diaphram for ground glass subsitute? I don't know much about these adaptors yet but I understand somewhat how they work. I see the two most comon are the spinning and vibrating. I would think that just a little vibration would suffice for a rubber or latex stretched surface (almost like a little trampoline for the image to show on) Maybe a better quality balloon, or condom(he he he) or similar will do stretched over a ring or frame or something. Just an idea.
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Old August 10th, 2006, 08:41 AM   #2
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It'd be interesting to see what the diffusion characteristics would be of stretched latex, but it wouldn't have an affect on how far the the "membrane" would have to vibrate. It seems like you were suggesting to vibrate the membrane in and out (the tramponline affect), but this is not the kind of movement you want on a GG. It has to be moving on the same plane in which is lies. Remember, the GG has to placed a precise distance from the front lens to be in focus. Trampoline motion changes the back focus (of course) and you would be left with a hopelessly blurry image. The idea is to blur the GG surface without blurring the image.

Even if the membrane were mouted to spin or oscillate like a normal GG, the inertia of the membrane itself might cause some kind of harmonic distortion, or ripples from the motion.

I think if anyone were to experiment with something like that, it would show most promise as a static adapter. So I wonder now what kind of an image you could project onto a stretched membrane. Maybe an interesting idea, but I'll stick with glass ;)

Has anyone ever tried it? Who knows... maybe we now have an alternative to wax for statics.

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Old August 11th, 2006, 02:16 PM   #3
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There has been the vegetable bag screen idea. I still think it is very promising. It's the thin kind of frosted looking bag you'll use for packing your veggies in the supermarket.
It is very transmissive causing very little light loss. However, the bags inspected so far do not diffuse evenly and hence cause very ugly bokeh. And, in most cases, the grain is visible.

Having said this, they are a great screen replacement if you need to experiment and don't have a frosted glass or wax screen at hand (that's just what I did last night).
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Old August 11th, 2006, 03:41 PM   #4
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If I only had one of those lenses that everyone is using on these adaptors, I could probably do some quick tests. Because I do have some latex rubber gloves (the white medical type) and I would use a ring shaped frame or something to stretch a section of the glove over it or maybe just over the end of a barrel(like just a simple piece of PVC plumbing pipe, say 3" diameter) attatched to the opposite side of the lens and produce an image on it then try to get a shot of the image with my GS400 macro focus. I think a simple test like this would see if any further research would be worth it. I'm sure that all rubber latex is NOT created equal (thickness, textures, colors) so trying different products (balloons, condems, gloves, etc.) may produce different results. And maybe this could be a static solution because if you stretch this stuff I don't think there would be much (if any) grain.
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Old August 15th, 2006, 10:43 AM   #5
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There is another substitute groundglass type title buried deep and past in the history back but having a slow landline I have cheated and used this one instead of hunting down the earlier post.

I bought some UV filters in to protect the remaining unprotected SLR lenses and have discovered that in two brands, sitting on top of the foam disk packaging in the crystal plastic filter cases, there now resides a thin plastic disk.

This thin plastic disk just happens to be of the frosted variety. It may be a bit to thick to use as a GG and might cause the image to look a bit low-contrast, however, for initial experimenters, making static devices, they would be an excellent starter.

The grade of finish is closer to AO3, than AO5 and a bit of aerial image creeps through. Put two together and much less of the aerial image comes through but the light loss starts to occur.

Two products are :-

Hoya UV 77.0s made by Tokina, - barcode (Australia)
is 0 || 24066 || 77003 || 5


Sigma 58mm MC UV, barcode (Australia) is 0 || 85126 || 91242 |||| 0 .

I wonder if the filter manufacturers are somewhat vexed by people taking to the final results of the factory worker's best endeavours with grinding paste and presenting people with a groundglass substitute to use instead. -

Would be a nice gesture, but I think it is more to do with stopping bits of the other foam material getting onto the glass and abrading the coatings in transit.
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