Replacing Fresnel and Ground Glass on a Speed

[Kevin Crisp]

Once you "flip it around" you've changed the plane of focus. (Not that I am sure what "it" is that is getting flipped.) Easy enough to test it.

[Jim Andrada]

I think the plane of focus is a function of the lens and where it is in relation to the ground side of the focusing screen, so not a big deal. What IS a VFBD (Very F--- Big Deal) is that you've changed the plane of focus RELATIVE TO THE FRONT SURFACE OF THE FILMHOLDER and while you may be saved by the "Other" DOF (ie depth of focus) it won't be optimal.

[maltfalc]

"the ground glass is the same thickness as the original fresnel. you can just flip it around and mount a new fresnel behind it."
the ground side of the ground glass is normally at the mid point between the fresnel and the glass. the fresnel and the glass are the same thickness. if you flip the glass around so the ground side is at the back with a new fresnel (of any thickness) behind it, the plane of focus will be exactly the same as it was originally.