Graflex.org

[AJSdave]

I am trying to determine if I have the correct/original Ektalite Fresnel in my Crown Graphic, S/N 891116 (year?), and if my assembly sequence is correct. Unfortunately, I've disassembled the ground glass/Fresnel from the Graflok back, and in trying to reassemble it, have run into some issues. After reading the many posts in the forum, I've come to believe that the correct (factory) assembly sequence was stated in a 2007 post by"45PSS" is as follows:

The smooth side of the ektalite screen goes toward the lens and is the first in the frame. Next the ground glass goes in ground side first. FRAME:ektalite screen smooth side;ektalite screen ridged side:ground glass etched side;groundglass smooth side:darkcloth:photographer.

When I try and install my Fresnel into the back first, It binds in the corners and will not sit flush with the mounting bosses. If I try and press it in, it bows, which is obviously unacceptable. If I reverse the sequence, i.e. put the ground glass in first, then add the Fresnel, everything lays flat as it should. Unfortunately, this is in contradiction to the assembly order that seems to be advised in the forum. I must deduce that 1. my Fresnel is not original, and 2. that this back has been incorrectly assembled for many years, although I've shot lots of great images, mostly at small apertures which may have given adequate depth of field so that it was never noticed before. I'd also mention that in making measurements of holders, back, and Fresnel/GG, that inserting the GG/Fresnel sandwich in backwards shifts the image plane (frosted side of GG) only about 0.015", which again, may have kept the problem from showing up in my images.

Any thoughts would be appreciated... Thanks

[bertsaunders]

AJSDAVE,
The frensil is made of plastic, and easily trimmed to fit with scissors, or sanded to fit!
The sequence of assy is correct, the rough sides go together, and the smooth side of the GG is on the backside, smooth side of the frensil is on the lens side!
Have a nice day........Bert

[Dan Fromm]

Dave, when you took the focusing panel apart, where was the fresnel located? And what are the bosses the fresnel and ground glass ride on like? How high? How machined?

[Henry]

Your s/n dates the camera to the period 1953/54.

[AJSdave]

Thanks for the information. I sanded down the corners of the Fresnel to allow it to sit flat on the back and have reassembled the back in the sequence posted in the original query. As a focus check, I shot an inclined yardstick with a Polaroid at 3' with a 135m lens at f4.7, first focusing on the GG. The image was sharp at the focusing point.

With respect to the back, it had bosses nearly flush with the casting, so I assume that it was designed to have a Fresnel. I believe that I measured the distance from the exterior surface (that mates to the camera where the film holder would) to the back mounting bosses at 0.135".

From measurements of a film holder, I get 0.195" from the film backing plane to the mating surface. Allowing for film thickness, this reaffirms the need for a Fresnel to correctly locate the frosted (image forming) side of the gg.

Thanks also for the information on date of manufacture.