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View Full Version : Graflok focus problem - HELP!!!



Scott --
30-May-2007, 11:37
Hey, all -

Ok, so I took a couple test shots with the new Graflock 4x5 reducing back. Came out like this:
http://i80.photobucket.com/albums/j185/bliorg/crop320.jpg

Hmm. That ain't right. Better check the measurements...

Alright, so I measure from an arbitrary point (the inside surface of the back) to the ground glass and, with 4x5 holder in place, to the film plane in the holder.

Hmm. That ain't right, either...

The two distances differ by about 1/4". Now, I had it in my head that Grafloks set the distance between the film plane and the ground glass to be equal, thus making it easier to use one for a cobbled reducing back. The Graflok is one I picked up used; the insert and ground glass are off of my Super Speed Graphic.

Anyone have an idea why I'm not getting agreement between the two focusing planes? Is there a way to adjust ground glass height on a Graflok back? Or is the insert I have specific to my Super Speed, necessitating another purchase?

Thanks for any help.
Scott

Scott --
30-May-2007, 12:25
Ok, here's my Graflok setup:
http://i80.photobucket.com/albums/j185/bliorg/IMG_1863.jpg

http://i80.photobucket.com/albums/j185/bliorg/IMG_1864.jpg

Here's a picture of a GG insert I found online:
http://i80.photobucket.com/albums/j185/bliorg/84c7_1.jpg

Is it possible that I have the wrong insert for this frame?

Sandeha
30-May-2007, 12:37
I presume you're saying that your glass is 1/4" further from the lens than the film. And if the glass isn't bedding close enough on account of it being from a different back, then ... I'll guess that you need a hacksaw and a grinder. There must be some lip or a pair of lugs that's preventing this glass holder from bedding in as well as the natural glass holder would do.

Those corners in the second pic look suspicious.

Though I guess you'll want to adjust the base, not the SSG part.

Nick_3536
30-May-2007, 12:42
Is it me or does the banister side look more in focus then the opposite side?

Scott --
30-May-2007, 12:49
Sandeha, that's as far down as the insert goes. I agree, it looks suspect. I'll post some pictures of what the insert looks like on the Super Speed vs. on the second-hand Graflok frame.

Nick, I just checked that on the negative. The plane of sharpest focus is on the stair right behind Braedan. I think this was shot around f/8 or so; in the big version (http://i80.photobucket.com/albums/j185/bliorg/crop320a.jpg), you can see the loss of sharpness in that banister.

Nick_3536
30-May-2007, 12:53
F/8. How close? You couldn't have had much DOF. Maybe you are chasing the wrong problem?

Scott --
30-May-2007, 13:03
Probably 6' or 7' away. It's very possible that the body of the camera was a little askew - gears slip every now and then. I'll chase that problem down next. Still, though, there's a quarter inch difference between where the film plane and the ground glass lie. It's not like that on my Super Speed Graphic...

Donald Qualls
30-May-2007, 13:04
Many/most Graflok backs originally incorporated a Fresnel panel between the ground glass and the lens; that will change the position of the ground glass, though not by any quarter inch. OTOH, the inserts I've seen sit down inside the Graflok, the same way a film holder would in a spring back, and the one you have clearly doesn't do so. I'd say that's your problem, though I now wonder if the rest of the back you have is actually a Graflok or something else that was misidentified (maybe even a "Graflex" back intended for the wider holders with a groove instead of a rib where they lock to the camera back -- those might well have a different registration distance, also).

BTW, I'd love to find one of those inserts...

Scott --
30-May-2007, 13:09
Donald, this one says "Graflex" in big red letters on the underside of the frame. Thought that just identified the manufacturer, but now I'm a little nervous...

scrichton
30-May-2007, 18:34
have you tried flipping the glass over? 1/4 inch seems a bit too much.

Glenn Thoreson
31-May-2007, 11:15
I told you,Scott, that Super Speed focus panel will not work on that back frame. You need the panel in the second picture.

rfesk
31-May-2007, 15:34
It seems to me from the photos that you MAY have a mismatch of the groundglass back and the frame. The frame that is attached to the camera is typical from a Crown Graphic Graflok back. The part that holds the groundglass is not what I usually see associated with that particular frame.

It seems that the ground glass back cannot seat all the way in the frame the way it is supposed to.

Bernard Kaye
1-Jun-2007, 15:08
As you know the film plane is 1/4 inch from the focusing surface of the ground glass, stop! Do what you have to do to put film plane and gg focusing surface in same plane with equipment you have. Perhaps measure from flat surface of lens board to film plane, to gg focusing surface?

If no go, "new" equipment will be less costly in money, time and frustration than 4 x 5' film, etc.

Simplistic, but is something reversed? Is difference same as difference to gg focusing surface from one side of insert to the other?

Then test at infinity with a large aperture. If OK, test at 100', 50', 25', 10'., etc., at large aperture.

Bernie

Scott --
3-Jun-2007, 12:20
Well, I'm pretty sure (from here and perusal at graflok.org) that there's a mismatch between frame and insert. I bid my way into one of the Pacemaker-type inserts today; when it gets here, (hopefully) the problem will be solved.

Update forthcoming...

Donald Qualls
3-Jun-2007, 13:43
Got my fingers crossed for you... :)

scrichton
6-Jun-2007, 07:53
Easiest and cheapest way to do this is shove the GG into a fidelity holderto use as a pop in screen. Make sure it is aligned flat to the area where the emulsion normally sits. This will save large expense of re-purchasing backs.

Scott --
6-Jun-2007, 09:20
Now that's an interesting idea...

FWIW, the new insert arrived today. Let it be known that the Super Speed/Super Graphic cameras take a different Graflok insert than t'other Graflex press cameras. Not interchangable. New one works perfect. Of course, I have no bellows on the camera now... :rolleyes:

Donald Qualls
6-Jun-2007, 13:17
Of course, I have no bellows on the camera now... :rolleyes:

Well, but that's progress, if I take your meaning correctly that the original is on its way to Hawaii to serve as pattern for a brand new bellows... :)

scrichton
7-Jun-2007, 03:13
Actually judging by my cheap solution on homebrew camera sites, it is by far one of the most common ways to make a quick spring-back and not worry about the offsets of the GG.

I have a cabinet maker who is going to make me a nice 8x10 so that should be a nice work around for measurements.

Hope the new back has sorted the issue