Question about the focusing screens in my Crown Graphic.

[Wheelie52]

After experiencing focusing problems with my Crown while using the rangefinder, which I calibrated to match what I was seeing on the rear screen, I worked out that the screen wasn't reperesenting the actual focal plane of the camera.

The camera has a 1.5mm thick ground glass and a 1.9mm fresnel screen ... the fresnel had been place on the lens side and after measuring the film plane distance in a film holder and matching it to the graflok I realised that this was obviously incorrect as the focus plane needs to be 1.5mm back from the face of the recess for the screens.

Obviously this means the ground glass is in it's correct position when placed matt side to the rear but what about the fresnel ... should the machined side be facing me or facing the lens?

It's probably an obvious question but not knowing how fresnels actually work I wouldn't have a clue.

Thanks in advance. :)

[Kevin Crisp]

The proper arrangement, if you have the original Ektalite Fresnel, is the ground glass on back with the frosted side facing the lens, then the Fresnel closer to the lens, with the ribbed side facing back toward the glass. Put another way, the ribs of the Fresnel are up against the frosted side of the ground glass. This obviously prevents you from confirming what is "right" by just measuring, which is unlikely to be right anyway with a Fresnel in front of the glass. So focus wide open on a line of something and then shoot film and see that the ground glass matches what the film sees.

Then, and only then, adjust the rangefinder.

A lot of these get put together wrong because people take them apart to clean them and then put them together like most other cameras, with the fresnel in back and then you're done for. Good luck.

[Wheelie52]

Thanks Kevin,

Much appreciated ... I searched the net trying to find what order the screens were supposed to be in but couldn't find the info anywhere. I tend now to use the Crown hand held a lot and noticed at shorter distances wide open it was focusing well behind my targets ... previously I'd used it for landscapes and still life etc at longer distances and smaller apertures so didn't see the problem until changing my use of the camera.

I've had it about three years now and it's a great camera ... I love it! :D

Thanks once again ... I'll shoot a couple of negs this weekend and check the results to see if it's sorted the problem ... I'm sure it will have.

[rdenney]

There are several FAQs on the Graflex.org website that describe issues like these, including how the Fresnel screens are properly installed and on which models.

Rick "who has been rooting around in those FAQs for a couple of days" Denney

[Kevin Crisp]

The factory instructions for setting up a Kalart (assuming that is what you have for a rangefinder) are very good but you have to follow them precisely. Don't skip the step that takes parallax into account at shorter distances. When you're done, check at all distances again. You may find you have to do the whole routine twice to get it right.

Be very careful of the one fragile screw that has the arrow pointing out which way it should be turned, it is very easy (and more intuitive) to turn it the wrong way and break it.

[Glenn Thoreson]

Make sure your focus panel was intended to have an Ektalite screen. There are two versions of the focus panel, one with the screen and one without. People often install a screen in the panel that's not machined to accept it and that puts the focal plane of the ground glass out of whack. When installing a fresnel in one like that, it should go outside the ground glass. If your clips fit properly and lay down flat, you're okay. Dull side of the glass forward. Fresnel in front of the glass, ridges rearward.

[John Clifford]

I echo Glenn's advice. My Crown Graphic has a spring back (non Graflok) which is not designed to accommodate a fresnel lens on the lens side of the GG screen. So I have my fresnel placed between the GG screen and me. I can touch the ridges with my loupe.