Problems With Focus On Besseler Mxt

[David Michael Bigeleisen]

I have a Besseler 4x5 MXT with a dichro head. I use it to print black and white. It has worked fine for quite a while. In the recent past, I have focused my image on the easel with a piece of paper under the grain focuser. After one or two prints, the images begin to be out of focus. Has anyone else had this problem? Can anyone suggest a solution?

David Michael Bigeleisen

[DanK]

There are a few possibilities as to the cause...

Manual fine focus knob gradually moving, to heat from the head causing a change in the plane (bow or buckle) of the negative...

To check the whether the focus is moving, simply focus on a negative - then leave the enlarger for a bit of time without using the enlarger - hour or so - then return and check to see if it still in focus...

If it is still in focus....may very well be heat from the head....

Thanks,
Dan

[natelfo]

probably heat. I have sat and watched 35mm negatives go out of focus over a period of about 10 to 20 seconds through the magnifier. I was using a condenser on my Beseler CB7, but with Dichro you still get some heat. IR blocking glass helps, but if you want true flatness, use a negative carrier with Anti-Newton glass. It can be a little bit of a pain to get all the dust off the glass (4 total surfaces) and the film (2 more surfaces), but you will not have to worry about film warping from heat. I bought one of the Beseler AN glass 4x5 carriers and could not live without it. Just be sure to keep a can of dust-off nearby and use it frequently.

[resummerfield]

...... I bought one of the Beseler AN glass 4x5 carriers and could not live without it.......

I suspect heat is causing the focus problem. When I started using a glass carrier, my focus problems disappeared.

[nolindan]

If you are having problems negative-to-negative when making large prints from 35mm then it may be the bottom bellows compressing when changing the negative carrier and moving the lens stage down an 1/8" or so.

The Beseler has a focusing lock that helps mitigate this. Problem is, I usually forget to loosen the lock when focusing and then wonder why the focus is so tight.