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View Full Version : Another New Way to Make a Focus Panel?



Mike1234
8-Dec-2009, 10:20
Okay folks... we have GG and parafin sandiches and combinations with fresnels. The parafin variety seems to be very popular making for better viewing but the parafin melts easily. Has anyone tried an epoxy sandwich?? Sort of an emulation of the parafin version.

1. Mix some slow curing epoxy with white medium (ultra-fine powder?) to make it milky and center a blob on the bottom glass.

2. Center the top glass and work it gently to mash the glue evenly between the sheets working it gently outward toward the edges and ensuring no bubbles are trapped.

3. Continue working the glue outward until it bleeds past the edges of the glass and forms a thin uniform layer of glue.

4. Use calipers on all edges/corners to ensure even distribution of glue and adjust accordingly by lightly squeezing.

5. Let the sandwich cure on a "flat" surface.

6. Use razer blades and solvent to trim/remove the excess from the edges and spill over on the exterior surfaces.

Worth a try?? It would certainly be less prone to heat problems.

Jack Dahlgren
8-Dec-2009, 11:56
Airbush some of that white medium onto a sheet of glass.

Mike1234
8-Dec-2009, 12:41
I would mess that up... I'd never get it anywhere even enough to use effectively. :)

Bob Salomon
8-Dec-2009, 13:14
Not that simple. You have to arrange that the imaging forming surface lies on the image plane in the back. Normally this is the ground side of the gg which is directly in the image plane. You want top make a sandwich which means that the imaging forming layer is now above the image plane by the thickess of the bottom glass in the sandwhich so your image is out of focus by that amount. So how do you cure this major problem?

Mike1234
8-Dec-2009, 13:40
Not if the inner glass is smaller so the outer glass rests on the mount. :)

Jack Dahlgren
8-Dec-2009, 13:42
Sure. There are dozens of ways to do this.
Be creative and maybe you will find a better way for all of us.

Jim Jones
14-Dec-2009, 02:25
Not if the inner glass is smaller so the outer glass rests on the mount. :)

Not so. The focus will be off by a fraction of the thickness of the inner glass, depending on its index of refraction.

gregvds
14-Dec-2009, 06:24
I think the focussing plane shift due to the covering thin glass inside the camera is explained on the bosscreen website.

I thought of trying this at home with microcristalline parafine, melting it, having it roughly between the two glasses, and then curing everything to the oven, hot enough to remelt properly the parafine, and then going slowly to cool to cold, to have the parafine curing, and the glass retracting without delaminating everything.

And then I received my Chamonix, and the GG/freqsnel is way better than on my Wista SP, and then I took pictures and forgot about making it :-)