Graflex.org

Les · Joined: 09 May 2001 Posts: 2682 Location: Detroit, MI

Well I just finished tearing down the focus panel of my promo Pacemaker as well as the focus panel for my Crown Special.

By looking at the front or the back, the frames LOOK identical. The same number--31915 is embossed in the frame on both with changes, slashmarks or suffixes. This is what threw me for a while.

By disassembling them I can see that the non fresnel back has a raised ridge that the ground glass sits on. The fresnel back shows that this rail was machined off of the mold. By measuring both of the backs carefully, and subtracting, I find a difference, or the height of the raised rail, is 0.045".

So there you have it. Nice an neat. They removed a .045" shim for the fresnel lens.

Now I've been researching Graflex for a number of years now and as soon as feel the "nice and neat" thought come on I know something's wrong.

I measured the thickness of the Ektalite screen.
Sure enough. It's 0.070".

So from the skills I got from my 2nd grade teacher. the Ground glass on the fresnel frame, when properly assembled will be 0.025" behind where the ground glass sits on the non fresnel lens.

Now I've never been one to buy into the fresnel has a focal lenght idea. But maybe that would account for the "less than full compensation" for the thickness of the fresnel.

Another theory is less scientific. If you look a the focus frame of from a Graflok back and a focus frame from a Graphic back, it's pretty obvious that the Graflok frame is simply a modification of the original. The original also has these raised rails and it's entirely possible they added the rails during the design to tweak the focal plane into perfect position.
When it came time to remove material to make way for the Ektalite lens, there just wasn't enough rail to remove. I hope to do some testing around this subject soon.

JIM23: I'd love to see how you make out on the suffix numbers and where they came from.

RE: perfect position for the fresnel lens. While Graflex chose to put the lens inside it was probably for more practical reasons than optimal lens theory. Graflex may have sold more 4x5 cameras than anyone else, but Ron Wisner has Sinar on his side of the fence.

The Sinar P had the fresnel lens on the operator side of the glass. This allowed the operator to use the fresnel for composition and removing it for critical focusing with a loupe.

It also allowed the lens to get scratched to all hell and cause the photographer to pay an incredible amount for a new one every few years, or more if he put it in his back pocket and sat down.

_________________
"In order to invent, you need a good imagination and a lot of junk" Thomas Edison

[ This Message was edited by: Les on 2003-02-24 19:53 ]

Jim23 · Posted: Wed Feb 26, 2003 2:13 pm Post subject:

Part numbers from examples:

Focusing panel frame from the Non-Ektalite panel was 31915. The panel is from a non-top-RF Pacemaker Speed Graphic 45 (ca. 1950?).

Focusing panel frame from the Ektalite-equipped panel was the same with a prefix of 2. Thus the part number on the panel was 2-31915. This panel is from a top RF Crown Graphic (dated 1968).

Jim23 · Posted: Tue Mar 04, 2003 5:35 pm Post subject:

More info...
In July, 1950 the Graflok back became standard (instead of the Graphic spring back) on the 34 and 45 Pacemaker series. These were supplied with a ground glass (no Ektalite). In May, 1951 the Ektralite became standard.

Info. from Used Camera review, Modern Photography, December, 1955 issue.

Les · Joined: 09 May 2001 Posts: 2682 Location: Detroit, MI

I've got 5 Graflok backed cameras

2 From '56 One without an Ektalite, but has the raised ridge.
2 from '61
and 1 from '73

4 have an Ektalite lens, but only the one from '73 has the 2- prefix

So it seems that the 2 prefix happened sometime btween '61 and '68, but the fresnel/non-fresnel was going on long before that.

Jim23 · Posted: Thu Mar 06, 2003 6:58 pm Post subject:

Your '56 model must be the "value package" that you indicated earlier. By then the Grafloks were the main offering. I also wonder if the Ektalite screen was a "delete option" for those who wanted a ground glass. I find that with a loupe, I have an easier time judging critical focus with the ground glass; however, composition is much easier with the fresnel lens with the better edge-to-edge brightness. What would be intersting is if someone could publish the Graphic/Graflex internal dealer catalogs, options, and price schedules for each year.

From your message above it is also apparent that the prefix of "2" on the casting for the focusing panel does not have any bearing on this. One is just a later revision.