Converting condenser head to"cold light head" via flashed opal glass difusion

[Bill C]

Trib, when you put the fresnel lens in, you just converted back to a condenser enlarger again. Probably the reason you lost a stop is because the condenser lens (fresnel) is not matched as well as the factory condenser. Good chance you would get the missing stop back by adding on another identical fresnel and centering them (ie, make sure they project the bright spot thru the enlarging lens aperture.

If there's any diffusion effect, it's probably mostly from light scattering at the edges of the grooves.

[N Dhananjay]

Dunno... It is also possible that the fresnel is basically taking the collimated light coming out of the condensors and directing it towards the edges (exactly, the way it does with a ground glass). In other words, it is un-collimating the light and making it diffuse. Just a thought. DJ