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Out of focus experiences

 
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steve@toprinting.com



Joined: 27 Sep 2001
Posts: 33
Location: Los Angeles, CA

PostPosted: Tue Feb 19, 2002 4:28 pm    Post subject: Reply with quote

What a great forum this is!! I'm sure someone here can help me.

When shooting with my new (to me) Crown Graphic 4x5 w/ an Ektar f7.7 & Schneider 135. Mounted on a heavy duty tripod. Most of my negs are slightly out of focus. Enlargements are not sharp and therefore unprintable. Lenses were set to infinity and both were IN FOCUS on the ground glass however. (There is no cam for rangefinder focusing.) No perspective adjustments were used. Polaroids looked good.

I have a few ideas why this happened, but would greatly appreciate any suggestions from this group.

My thoughts are:
1. Perhaps I was stopped down too far (f32 & f45) and lens defraction occured causing the focus to shift.
2. Maybe (outside chance here) the lenses in question need to be adjusted (shimmed) by Mr. Grimes for better sharpness.
3. OR - The film holders used that day did not place the film in the exact same plane as the ground glass plane. If this is true, how do I test and adjust without using up a box of film? I have 14 holders about 1/2 plastic and 1/2 wood.
4. OR - According to my wife, I can't see what I'm doing. Possible, but not likely.

Thanks for your responses.



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alecj



Joined: 09 May 2001
Posts: 853
Location: Alabama

PostPosted: Tue Feb 19, 2002 6:20 pm    Post subject: Reply with quote

1. Not likely.

2. Not likely.

3. This was where I was headed. Until I noticed you said "Polaroids looked good".

4. Looking better by the minute.

Actually, I would first do the "fence" test. Set up along a fence, focusing carefully [on the ground glass - with a good loupe] at a specific point halfway along the fence. Make a note if the distance scale on the bed, and the rangefinder image agree. Expose, [repeat several times to check repeatability of the error] develop and proof [proofs are sharper than enlargements].

If everything was correct, the negs should be sharp. If the focusing error is uniformly off, then either there is a problem with the way the holders are seating in the back, or more likely the film isn't on the same plane as the focused image. Once you've got that point fixed, then you can adjust the scale and rangefinder [you said no cam, but if it is a side RF, there is no cam. The adjustment is done manually, But, for only one lens.] Sure sounds strange to me, though. I don't think this is a routine problem. Perhaps someone removed a fresnel lens which messed up the positioning of the ground glass.

One more thing. Do the test with only one lens at a time. You mentioned two lenses. That's one variable too many! Do it with one, then the other.



[ This Message was edited by: alecj on 2002-02-19 10:24 ]
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45PSS



Joined: 28 Sep 2001
Posts: 3233
Location: Mid Peninsula, Ca.

PostPosted: Tue Feb 19, 2002 7:26 pm    Post subject: Reply with quote

1) Find a copy of Photo Techniques May/June 1999 and read the article Improving View camera Sharpness then test your camera, or
2) Remove the back from the camera. Get a piece of flat bar approximately 1/8 thick by 1 inch wide, a flat toothpick, piece of thin flat wood or as I do, a narrow stainless steel ruler, some tape or small clamp. Lay the flat bar on edge across the center of the back. place the piece of flat wood perpendicular to the flat bar at the center of the ground glass and tape or clamp it to the flat bar. If using that narrow stainless steel ruler take care not to scratch the gg.
Install a scrap piece of film into a film holder and insert it into the back, remove the dark slide, and place the flat bar with the flat wood attached back to the same place it was at first. The piece of wood perpendicular should just touch the film surface. If it does not try another film holder. Once a consisent varriation has been established shim the ground glasss to the correct position.
I do have a plastic film holder with one side correct and one side 1 1/2 film thicknesses deeper!

Charles

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steve@toprinting.com



Joined: 27 Sep 2001
Posts: 33
Location: Los Angeles, CA

PostPosted: Wed Feb 20, 2002 8:30 pm    Post subject: Reply with quote

To my friends, Alecj and 45PSS,

Holy Zone System Batman!!

Thanks so much for your insightfull and very accurate assistance. BTW it all worked!

I found the magazine article you recommended and followed your posting. Bingo! Problem identified immediately.

With a metal straight edge across the GG frame and a toothpick clamped at right angle to it, I measured the depth to the GG face from it's frame. Then transfered the "jig" to a film holder. The toothpick never touched the film in the holder by what looked to my eye at a short 1/8". I then loosened the hold-downs on the GG and slipped in shims made of a memo pad cardboard backer 0.022" 1/8" x 4". Took several tries but finally got it to match the same "set-back" as the holder. 4 shims like this did the trick with a total thickness of .088". This moved the GG back from the lens by that amount. (The only residual problem doing this is that the focus hood won't snap in as before, but I'll take care of that later.

Now, the GG plane and the film holder plane agree. I then re-set the infinity stops outside and shot a polaroid at wide open f stop at an object 15' away focued on the GG back with a loupe. As it really should be - the forgorund was blurred, the focused object was sharp and anything behind that was blurred. As a second test I shot again without changing the focus @ f22 and perfect sharpness front to rear, as it also should be.

I also checked all 14 of my holders and all measured within a hair of the same set-back for all of them.

Took about 2 hours for the entire process.

Time very well spent.

You guys are awsome!.

Thanks again.

Steve Feldman, Van Nuys, CA

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45PSS



Joined: 28 Sep 2001
Posts: 3233
Location: Mid Peninsula, Ca.

PostPosted: Wed Feb 20, 2002 8:43 pm    Post subject: Reply with quote

Moving GG far enough back to prevent focusing hood from attaching may suggest wear or biuld up preventing film holders from seting properly.

More work; just put a cusion on the floor for Ansel's jaw to hit, I do.

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steve@toprinting.com



Joined: 27 Sep 2001
Posts: 33
Location: Los Angeles, CA

PostPosted: Wed Feb 20, 2002 8:53 pm    Post subject: Reply with quote

OUCH!

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