Out of focus negs from Crown Graphicgreenspun.com : LUSENET : Large format photography : One Thread
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 7 plastic and 7 wood. 4. OR - According to my wife, I can't see what I'm doing. Possible, but not likely.
-- Steve Feldman (firstname.lastname@example.org), February 19, 2002
One potential cause for "in focus on groundglass/out of focus on film" images can be the incorrect installation of a fresnal focussing screen in the camera back.
The backs intended for use with a fresnal screen (I think these may all be Grafloc-type)make provision for the additional thickness of the screen. If the screen is missing from a "fresnal-intended" back or someone has incorrectly installed a fresnal screen in an earlier "not fresnal-intended" back, then the groundglass and film plane will not be in the same location relative to the lensboard.
Try measuring the depth of the groundglass in the back on your camera; remove the fresnal screen (if any) to do this. The depth of the groundglass should be identical with the depth of the film plane in the film holders which you are using.
-- Ed Balko (email@example.com), February 19, 2002.
Steve: "Slightly out of focus" everywhere? Or is it sharp behind or in front of the subject? Is the fresnel in front of the ground glass?
-- Kevin Crisp (KRCrisp@aol.com), February 19, 2002.
I had the same or similar problem with my Speed Graphic Pacemaker (2X3)a while ago. One of the possible culprit will be the rail lock being a bit loose. Try to tighten it and see if the rail has no movement. If it is loose, when you focus the image appears sharp but when inserting the film holder a slight move will cause the bellows/rail to move thus creating unsharp image (you can not re- focus because you have no rangefinder). I find the rangefinder useless, it does not help much given a number of lenses one might use. Secondly, it is possible that your film was improperly placed in the film holder thus causing it to bulged, check that or you may want to run your finger on the inside edge of the film holder when finished loading to check if it is properly loaded - (do not worry, the residuals from your fingers gets washed when developing).
That's my $0.2
-- Adrian Ng'asi (firstname.lastname@example.org), February 19, 2002.
Steve, you must be focused past infinity, otherwise you would be seeing part of the foreground in focus. If your Polaroids are Ok, then the problem is confined to the way that your film holders are mounting in the camera, right? For the film holders to be in a position past infinity focus, they must be placing the film too close to the lens when the standard is racked all the way back to infinity. Odd, that. You know, if you're just checking focus you can use photographic paper instead of film. That would be a lot cheaper if you need to do a lot of trial and error. Good luck.
-- Dan Carey (email@example.com), February 19, 2002.
When you say your polaroids are in focus, do you mean a 4x5 polaroid image? Checking the 4x5 image that the Polaroid produces isn't terribly helpful since it can look fine even when things are pretty far off (due to no enlargment). Try using a Type 55 Polaroid (positive negative black and white film yields a small "contact" print and an enlargable negative)and enlarge the negative. That would demonstrate whether the polaroid was actually in focus, or if it just looked acceptable in contact print size.
That's where I would start. If the polaroids are in focus when enlarged, it's a problem with the film holder/camera junction. The holders could be warped (probably not with the plastic ones though) or you could be putting the film in wrong (see previous post on bowing the film).
With the film that is coming out out of focus, try focusing on an object set on grass about 10 feet from the camera (well within infinity focus, using a low tripod). When you enlarge the negative, some grass should be in focus, either behind or in front of the focal object. The grass that is in focus should be a line in focus from edge to edge, fully across the print. If it is only in focus at the edges, or in the center, your film is probably bowed.
-- Andrew Cole (firstname.lastname@example.org), February 19, 2002.
I would first check at Graflex.org and make sure the ground glass and fresnel lens is all there and installed properly. It sound like something is way out and this one would do it. Many (all?) of the graphics had the fresnel between lens and ground glass. This complicates the proper positioning of these elements. If the GG or fresnel was replaced at some time, it could have been messed up.
-- Gary Frost (email@example.com), February 19, 2002.
Steve: I suspect as a couple of others have mentioned that you either don't have a Fresnel lens installed or it is on the wrong side of the ground glass. You can check that by removing the lens board and seeing if you have glass or plastic facing the lens. If there isn't a plastic screen with fine line circles there, check at the back of the ground glass. If it is at the rear or missing, you need to move it to the front on the Graphic or get a Fresnel. You can also look at the ground glass while focusing to see if the corners darken. If so, your Fresnel may be missing. The ground side of the glass must face the front also. The position of the ground glass is critical with LF cameras.
-- Doug Paramore (Dougmary@alaweb.com), February 19, 2002.
To my friends, Ed, Kevin, Adrian, Dan, Andrew, Gary and Doug -- And Alecj and 45PSS at Graflex.org
Holy Zone System Batman!!
Thanks so much for your insightfull and very accurate assistance. BTW it all worked!
I found an article in Photo Techniques magazine that was recommended and followed all of your postings as well. Bingo! Problem identified immediately. Great minds do think alike.
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!.
Steve Feldman, Van Nuys, CA
-- Steve Feldman (firstname.lastname@example.org), February 20, 2002.
With all due respect to Jack East's talent as a photographer, his suggested technique for measuring ground glass/film plane coincidence falls far short of anything close to accurate. It actually measures nothing! At best it is a means of gross comparison and might alert you to a very serious problem. The results of such a test should not be used as calibration guidelines for changing your gg position. It can get you into trouble. On a different, but related topic, the use of cardboard as shims should be considered a temporary patch as opposed to a permanent fix. Cardboard is hydroscopic, can and will change dimension over time and is also very compressable. The use of Mylar or brass shim stock is advised for spacing out your gg. This material can be purchased in readymade known thicknesses for this purpose. There are some other subtlties you should be aware of: Theoretically, the gg placement should be perfect (zero tolerance) with respect to the published specification of film holder depth less thickness of film that is used (or average of film thicknesses used). Using any holder as a benchmark for adjusting a gg is a no no. The spec for a 4x5 holder is +/- .007". If you happen to use one(s) that are off and calibrate your gg to that (and you will never be able to do this with toothpicks and rulers, trust me), what happens when you get a holder that is on the opposite end of that tolerance? The holder may be in spec., but the gg is off in the other direction and your negatives will be less than acceptably sharp! If you have all the correct parts and assemble them in the correct order, the chances are very good (with a Graphlex) that the gg will be where it should be. I would recheck that and make certain there isn't something missing or reversed in orientation. My article on gg alignment and testing is on its way to you by email.
-- Robert A. Zeichner (email@example.com), February 21, 2002.