View Full Version : Help with focusing problem

Steve Seitz
2-Jul-2000, 15:42
I have just lucked?? onto a Burke and James Orbit monorail 4x5 as a first stab a t LF work and have run into a focusing/resolution problem. I have only used the camera once, but am stumped as to how to address this problem so I can move ahea d with learning to make it a practical part of my amateur work.

This is an all-metal camera (which I understand to be rare for B&J cameras) and is likely a mid-60's model. I got it along with a Polaroid 500 back in decent sh ape - in fact the whole camera is in fairly good condition. It has a Synchro Com pur shutter (which sticks a lot at slow speeds, and is a bit spotty at higher sp eeds - needs cleaning and adjustment)with a Schneider Kreuznach Xenar 150 mm, f4 .5 lens which seems flawless.

The problem: poor focus using the polaroid back with 100 iso B&W film, which is the only film I've tried so far. Focus is extremely soft below f16 and at 4.5 is unusable. At f22 and f32 it is decent but not great - at least not as great as I'm led to believe LF should be or as good as I've seen published.

My perplexity comes from the fact that on the ground glass, at any aperture, foc us is excellent, using an 8x loupe, but when I put in the polaroid back and shoo t I get very poor results. I finally noticed that the ground glass frame doesn't seat well (maybe as much as 1/16th in. off the camera body) and you have to fut z-around with it to get it close to firmly seated. Even then, one corner is 1/32 or so off the camera. Correcting this seems to have helped some, but still at o pen apertures very fuzzy.

Why would it focus correctly on the glass and not on the film? Could the Polaroi d back not be suited to the B&J body? Am I putting the film packet in wrong? Am I focusing wrong? Am I expecting too much? Is the Polaroid film simply very grai ny even at 100 iso?

I would like to be able to do outdoor portraits (I normally shoot landscapes etc .), but having to use only the higher apertures means I can't fuzz-out the backg rounds enough to get a good head shot. It also means if I'm shooting close folia ge and there is a breeze I get blurring because I have to shoot at such slow spe eds for the high aperture.

Am I doing something wrong, overlooking something, or is there a mechanical prob lem?


Doug Paramore
2-Jul-2000, 16:03
Steve: Sounds like to me the ground glass and film plane are not in the same plane of focus. Try the following: 1. Make sure the ground glass holder is tight against the back with no play. Make sure the ground glass holder is not warped or the springs too weak. 2. Make sure the ground side of the glass is toward the lens. Sometimes folks take the back apart and put the glass in wrong. 3. Take off the lens and measure carefully from the edge of the lens opening to the ground glass (through the bellows). 4. Put the Poloroid back in place with a sheet of film in place. Measure from the same spot on the lens opening to the surface of the film. The two measurements should be the same. If they aren't, you may need to shim the ground glass. Someone could have removed, or added, a Frenel lens which could throw the focus off. The distance from the lens to the glass and lens to the film surface must be the same within a couple of thousandth of an inch for the focus to be correct. The 150mm Xenar lens is a good lens and is quite sharp.

David Richhart
2-Jul-2000, 17:17
Gee-whiz Doug...sounds like you've pretty well covered the things that I would look for! You must have had a few nightmares in the past too. ;0D

2-Jul-2000, 18:08
Steve, I nearly went crazy trying to adjust the infinity stops on a Technika using my old 500 Polaroid back. Then I realized that, unlike the newer backs, it has no spring guides to hold the edges of the film in place, and it was jiggling around at least 1/8." Everything was perfecty easy and consistant after I changed to a 545 back. Mitch

N Dhananjay
2-Jul-2000, 18:36
I would definitely check the registration of ground glass and film plane. That is, you want to make sure that the ground glass is exactly where the film plane will end up. Very often, especially with the older cameras, ground glass/fresnel combinations are put in the wrong way or shims or lost etc. The easiest way to check if this is the problem is to stack a few playing cards together so that the edges sort of overlap. Now focus on the middle one till it is sharp on the ground glass. Expose and develop the film. Study the film carefully. If the card you focussed on is not sharp but some other card is, odds are this is your problem. If you lack a deck of cards, you can also try this with a scale or ruler set at an angle to the camera. Focus on the middle, say the 6" mark and expose and develop to see if the 6" is soft but some other marking is sharper. This might also explain why stopping down seems to reduce the problem without eliminating it. If its just an overall softness across all cards, maybe theres a problem with your lens (the elements could be mis-centred etc). Good luck. DJ

2-Jul-2000, 23:23
I use 405 back which costs less and I did observe polaroid proof is not as sharp as film(using fuji quickload), but, like what you've said, it's decent. I suggest you try a couple slide film first before drawing any conclusion.

Doug Paramore
2-Jul-2000, 23:28
Note to Dave: You're right about the nightmares with cameras. When I was just starting out in LF (about the time the earth began to solidify and cool) I bought a Calumet view camera of dubious vintage. Someone had added a Fresnel lens in front of the ground glass and also turned the ground glass around so it faced the back. It wasn't possible for the film plane and ground glass to line up. Talk about a major disappointment. A kindly old studio photographer took one look at the back and in five minutes with a screwdriver I had sharp pictures. I wish I could thank again all the old photographers who helped me when I was first learning....there were no web sites like this one back then where one could get help and opinions. Unfortunately, those old guys have gone to that great darkroom in the sky where I am sure they are still making great photographs with their Graphics and Linhofs. Good shooting.

Steve Seitz
3-Jul-2000, 17:09
Thanks for the great suggestions - I wondered about the ground glass possibility but didn't check it out. It does have a fresnel screen so someone may have put it in backwards - I'll check it out today and let you know. If it is a no-go, I check the registration etc. It is very dishearten to come out with a first batch that is lower quality after all that effort and anticipation. Never-the-less, undaunted he moves on (lots of windmills on the horizon!)

Steve Seitz
3-Jul-2000, 19:39
This is a couple hours after my last message - turns out someone had added a fresnel lens in front of the ground glass. Took it out, and also made some adjustments to the holder - the bail lever was preventing the holder from seating completly. Took two shots - great focus!

Thanks so much for your help. Great discussion.

Doug Paramore
5-Jul-2000, 11:16
Steve, glad you got the old B&J up and running. You can make some nice images with that camera. You said you took your Fresnel lens out...did you mean completely? If you want to use it, put it behind the ground glass with the smooth side toward the film holder. The Fresnel lens helps brighten up the corners, but not everyone likes them because of the pattern engraved on them. Your call on whether you like it or not. Good luck with your entry into large format. stay with it and you will make some great images for the wall or gallery.