Quote Originally Posted by SchwinnParamount
... or as I learned, if your camera has a fresnel lens in front of the existing ground glass then you will still have to use that fresnel lens with a new ground glass or you won't be able to get a sharp image on your negative.
If you have a fresnel and decide not to use it, you will have to measure the fresnel thickness and then shim the ground glass that same thickness to maintain the correct focus registration.

Dave