Source for Crown Graphic ground glass

[Louis Pacilla]

Hi Bob

Call Jim @ Mid-West Photo in Columbus. I know for fact that he had both Crown/speed ground glass & fresnel lens for sale . There was plenty of stock the last time I visited the store (About a year ago).

The GG & Fresnels that Jim sales are correct size & great quality . In fact I bought the fresnel & it fit perfectly (in proper position).

Give him a call & I bet it'll be on it's way & will answer your needs.

[Ivan J. Eberle]

You'd need to measure the depth, preferably with a depth gauge or a dial indicator, from the flat of the back where it faces forward (the "gate" that I was referring to above) to the step or flat where the piece of plexi rests. It should work well enough to measure where the plexi is in relation to the gate but suggest you measure near the edge.

You're going to need some kind of instrument to do this; a cheap set of machinist's set of calipers will be about the most difficult of all method yet is probably adequate if you turn it around to measure the depth. (Get digital calipers if you're buying new, they measure in both metric and English, and zero out with the press of a button).

[Bob Kerner]

So here's what I have. I was mistaken. Now that I have it out of the camera it's definitely glass, though the edges are not even. There is only one element. I don't have calipers to measure the depth. Is there any other way to know whether there would have been an Ektalite in there? There appears only to be enough room for this piece of glass.

It may just go back to the seller. There are also tiny holes on the lens board (3d photo) that at first I thought was a missing logo, but now I wonder if they don't go through the board entirely since it seems like someone tried to patch the back of the board with a red sticker. Not sure whether to make this into a repair project or return it.

[tbeaman]

It looks to me like this was not made for an ektalite. Measuring is the sure way of knowing (and tedious and annoying), but check the inside edge where the glass goes. Are there little ridges on each side? It looks like there are in the middle photo above. Those "bosses" compensate for the lack of a fresnel. That surface will be totally flush if they're not there.

Replacing the ground glass is a simple (especially if the ektalite is unneeded) and usually expected task, and a couple of holes in the lens board are easily patched about a thousand different ways (or you can get a new board). Those two items could hardly be worth any price differential, so why return it? Go shoot and be merry!

Finally, just to be clear about the bosses:

[Ivan J. Eberle]

Another (perhaps simpler) way to confirm focus registration of the GG with the correct depth for a film holder is to insert a film holder loaded with film and shoot with the lens wide open.

Insert a ruler or yardstick into the image, at an oblique angle, focused on a specific rule marking... the developed sheet of film examined under a loupe will confirm either that you're bang on (and there is no problem) or that you have more work to do (measuring, acquiring an Ektalite screen instead, or shimming a plain GG).

[Neal Chaves]

I don't like Fresnel lenses on my ground glass, but I love the TRF Crown Graphic Special. After some careful testing with Polaroid PN 55, I found that the Fresnel changes the effective extension by less than its thickness, because it is a lens not just a spacer. I calculated the thickness of a spacer that will give correct focus on both the film and the ground glass as .032".

There is a gray plastic material available in 1" strips in the model railroad section of big hobby stores that is exactly this thickness. I cut thin spacer strips of this and epoxied them to the edges of the ground glass and have enjoyed accurate focus ever since.

[BetterSense]

You're going to need some kind of instrument to do this; a cheap set of machinist's set of calipers will be about the most difficult of all method yet is probably adequate if you turn it around to measure the depth.

You can easily accomplish this with nothing fancier than a straight edge, a clothespin, and a toothpick. Just lay the straightedge across a film holder, and clamp on a toothpick and adjust it to just barely touch the surface of the film. Then you can lay the straightedge across the camera back and judge the distance to the ground glass. You can easily judge +-.005 inch by eye.