Graflex Replacement GG/Fresnel Lens

[BrianShaw]

Yes… that’s right. Ribs of fresnel and ground of glass are in contact with each other; Ektalite is on the lens side.

[Rod Klukas]

You cannot put a fresnel on the lens side of this setup. If you do it will move the focus 2/3 the thickness of the fresnel. But if you add a fresnel on the outside, on top of the fresnel, it will brighten the image, but not throw the focus out. This is what Sinar and Linhof, on some cameras did, to make their screens brighter.

[westpost]

You cannot put a fresnel on the lens side of this setup. If you do it will move the focus 2/3 the thickness of the fresnel. But if you add a fresnel on the outside, on top of the fresnel, it will brighten the image, but not throw the focus out. This is what Sinar and Linhof, on some cameras did, to make their screens brighter.

What if the fresnel was originally in that position (lens side of the gg)? That appears to be the case here.

[Rod Klukas]

You cannot place a fresnel in front, or on the lens side with this Graflex setup, as it will move the focus 2/3 the thickness of the fresnel. And so the film will not match the ground glass.
You can add a fresnel on the viewing side of the glass, or the back, as the image is still formed on the ground side of the glass. So no conflict. Use glass for the ground glass, as any flex in the focus plane, will cause focus issues as well.
Wista had a combo screen that works quite well with a clear glass cover. If you can fit that, you are in great shape.

[rfesk]

The Graflex discussed in this thread was manufactured with the Ektalite (fresnel) lens placed in front of the groundglass (between lens and groundglass.)

What you are saying is correct in most cases UNLESS the camera was designed to operate the other way as discussed above where the location of the groundglass/fresnel arrangement is taken into account when locating the plane of focus.

[spacegoose]

Yes… that’s right. Ribs of fresnel and ground of glass are in contact with each other; Ektalite is on the lens side.

Thanks for the info! Is this documented in the manual? I can't seem to find it here: https://graflex.org/manuals/45-Pacem...wn-Graphic.pdf

I just replaced my ground glass and believe my Fresnel's rough side was facing the lens.

I'm not sure it's an after market Fresnel or if it matters? Is there a way to differentiate the factory Ektalite Fresnel from others?

My camera is a 4x5 Crown Graphic, Graflok back, 135mm Optar and Graphex shutter.

I placed everything in the orientation you specified. The focusing and screen look good but I guess I'll need to shoot some film to know for sure.

[Kevin Crisp]

Brian's 8/7/23 post explains the right way the gg and the Ektalite fresnel are supposed to be installed. On the taking lens side of the fresnel (i.e., closer to the front) it should be smooth, with the ridges facing the rear.

[Dan Fromm]

You cannot put a fresnel on the lens side of this setup. If you do it will move the focus 2/3 the thickness of the fresnel. But if you add a fresnel on the outside, on top of the fresnel, it will brighten the image, but not throw the focus out. This is what Sinar and Linhof, on some cameras did, to make their screens brighter.

But Rod, Graflex made some, not all, Pacemaker Graphic focusing panels with a fresnel in front of the ground glass. The GG rides on bosses. Focusing panels made for use with GG + fresnel have low bosses, focusing panels made for use with GG and no fresnel have higher bosses.

[BrianShaw]

From Section 6 of the manual linked in post 26:




On the same page are measurements of the bosses on the various versions of the back.