Frosted Plexiglass => Aerial focusing conversion

[dh003i]

Per Bruce Wehman's suggestion, I am using he plexi ground glass with my Wehman. Talking with him about an aerial focusing solution, he suggested using his plexi GG (plexiglass with windowfrost affixed to it) and cutting off the windowfrost with an exacto-knife.

I have started doing that. It works great! I have 4 more strips to cut off (to make a grid of "thirds"), but here are the results as of thus far. You focus on the grit of the ground glass with a 20x loupe, and then an aerial image is in tack sharp focus. I'll probably make shims to keep my jewelery fold-away loupe always the right distance from the GG.

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[Nathan Potter]

Yes! I have a couple of 4X5 GG from Linhof with the same aerial (clear) sections as you have drawn. Absolutely the best system for critical focus. If critical area does not fall in one of the aerial slots a quick rotation of the camera will get you there. Critical viewing at the corners is tricky with wide angle lenses but a large aperture or tilting loupe will help.

I've had some luck using platers waterproof tape to mask the clear areas when grinding my own screens in 8 X 10 size.

I wish Linhof still made the 4X5 size - or do they Bob?

Nate Potter, Austin TX.

[vinny]

I'm suprised Bruce didn't tell you to leave your wehman at home!
I can't imagine trying to shoot from any aircraft with an 8x10 that isn't made for such purpose.

[dh003i]

Nathan,

This seems like a pretty cheap option -- plexiglass and windowpane frosting stick-on backing. Bruce Wehman told me it is a good frosting layer that really sticks on well.

Here is a picture of the "final" result -- I just need to remove the "grime" off of the plexiglass from the sticky stuff left over. I figure I'll wait for it to dry out a little then attack it.

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[Peter De Smidt]

So the advantage is that the aerial image is grain-free, right? Does that really allow you to focus more precisely?

[dh003i]

The aerial image is grain-free and much much brighter. So it allows more accurate, easy focusing; it also makes it easier to focus on dark subjects.

I should take a picture with a macro lens focused on the frosted part of the glass, so that the aerial image will also be in focus (would that work?) to illustrate.