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focus problem with Crown Graphic
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tfalk
Joined: 11 Dec 2008
Posts: 13
PostPosted: Mon May 17, 2010 4:52 pm   Post subject: focus problem with Crown Graphic

I own a 1964 Crown Graphic and I have testing it to ensure sharp negs. It does have its fresnel, its installed correctly. I do not use the rangefinder. I simply set up a shot and focus with a loupe. All looks good. The negs look soft. I don't care about the rangefinder ability, only a smaller 4x5 to use occasionally instead of the monorail camera. Any ideas on the sharpness issue?The lens is a Schneider Xenar 135mm f/4.7. I stop down to approx. 22 for the test shots.

thanks
45PSS
Joined: 28 Sep 2001
Posts: 4081
PostPosted: Mon May 17, 2010 6:20 pm

1. Check your film holders for correct film placement depth.

http://home.earthlink.net/~eahoo/page8/filmhold.html

Remove the dark slide, put a sheet of film in the holder, lay a straight edge across the holder and measure from the bottom edge of the straight edge to the surface of the film. It should be equal depth across the width and length of the holder. Check both sides of all your film holders. I have had holders with one side off.

2. Remove the complete camera back. Graflex used different diameter and different length screws to hold the camera back on so note their original position when removing the screws. An improperly placed screw can damage the camera.

Standard ground glass placement measurement
With the camera back off, insert a film holder with a sheet of film installed and the dark slide removed. Lay a straight edge across the camera back frame making sure that the straight edge does not sit on a high bump on one side (all camera backs are not even around the edge), and measure from the bottom of the straight edge to the film surface. Record the measurement. Check the distance at several places, they should all be the same.

Next remove the film holder from the back and measure to the surface of the ground glass. It should be the same distance you recorded for the film. Shim the ground glass so that it sits at the film plane if it is too close; mill the frame edge down if it is too far away.

With the fresnel in front of the ground glass you have to add the thickness of the fresnel to the measurement to get a correct reading.

A focus panel factory equipped with an Ektalite Field Screen (Graflex speak for fresnel) will have short bosses that the ground glass/fresnel sandwich sits on.
alecj
Joined: 09 May 2001
Posts: 853
PostPosted: Tue May 18, 2010 4:15 am

What about your camera support? Adequate?

And, how are you tripping the shutter? Good cable release used gently.

These items are best tested by shooting night scenes containing lots of light bulbs. That would rule out camera shake.

Can you borrow another lens to make a test on it to rule out camera body alignment?

The items listed by 45PSS are the most likely culprits based on the info so far.

It would be nice if you could post some pics here demonstrating the problem.
Dan Fromm
Joined: 14 May 2001
Posts: 2165
PostPosted: Tue May 18, 2010 9:54 am

What magnification do you use when looking at your negs? I ask because at 10x everything looks soft.

Have you tried shooting a subject that isn't parallel to the film plane -- for example, a brick wall or picket fence at 45 degrees to the film plane -- with the point of focus clearly marked? This will let you see whether the problem is focusing or something else.
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