Dust Between Fresnel Lens and Ground Glass Screen

**Peter Henley** · 11-Apr-2011, 04:37

Hi,
I've just taken the plunge into LF and have bought a Toyo 45G. The camera is in perfect condition, but absolutely filthy. There seems to be dust/dirt between the ground glass screen and the fresnel lens which would appear to be easy to remove by disassembling the back. However, the manual cautions against this because it will displace the focal plane, which will then require a correction. How much of a problem will this be and can I correct this myself?
Cheers, Peter.

**darr** · 11-Apr-2011, 04:58

Peter, I would not attempt to take it apart if this is new to you. Most of the time, the ground glass is shimmed into place for correct focusing onto the film plane. I do not know where you are located, but I once sent a Linhof to Bob at Precision Camera Works for ground glass replacement. I am sure others will chime in to help you as well.

Kind regards,
Darr

**Robert Crigan** · 11-Apr-2011, 11:58

'However, the manual cautions against this because it will displace the focal plane, which will then require a correction. '

Don't worry about it. The image is focussed on the matt side of the ground glass and the fresnel only redirects the focussed image. My Sinar has the fresnel in a loose frame clipped behind the ground glass. My 45 field camera has the fresnel sandwiched to the lens side of the ground glass. Don't know why but that's the way it came. I've tested it on either side and it makes no difference.
My advice: if you can dismantle the fresnel/ground glass without risk of trouble, go for it. The image lives on the ground glass.
Robert

**TheDeardorffGuy** · 12-Apr-2011, 21:21

Just do it. Look for any shims if they exist. Mark where they go. Now heres the problem. The lines. They may come off if you wash it. Windex is a pretty strong solvent. I would not use it. I use a sink of warm water and a drop of clear dish washing liquid. Let it soak a while and dry on a well used dish towel. Let it air dry overnight and reassemble. If the lines flake off the glass get a #4a Drafting pencil and draw some back on. Have fun.