ground glass point of focus

[adrian tyler]

i have to modify my 4x5 - 6x9 reducing back as the glass is not parallel to the filmplane, the question is, where is the point of focus, (ie. what point should i measure to adjust to) the back of the GG, the front of the GG or the part between the 2 GG perspex sheets?

thanks

adrian

[Dave Parker]

Adrian,

Depending on the camera, normally your focal point will be on the ground side of the ground glass, which should be on the lens side, in most cameras......but it will also depend on if you have a fresnel in front of the ground glass.

Dave

[adrian tyler]

hi dave, it's an ebony 4x5 - 6x9 reducing back, there are 2 pices of material, one a clear glass piece (lens side) then a perspex piece which has circular groove on the lens side and has a matte finish with the grid drawn on it on the outside.

i assume then that it will focus where the glass and perspex meet?

funnily enough i think i'll be upgrading to a "satin snow" which someone has kindly offered, i imagine it will be the same setup?

many thanks.

adrian