You are right, that indeed could be the case. Most "condenser" enlargers are somewhere between a perfectly collimated point source and a diffusion source. So, on the LPL the focus of the condensers may not be super critical.
Originally Posted by ath
I guess most important is to check various combinations of the condensers and see which combination actually is the most even under your conditions.
I high contrast print with no negative can be very revealing ;)
This is obviously academic if you have an 80mm lens that you can use and gives you sufficient enlargement, but your 50mm lens might be at fault. Were you trying this at full aperture?
Originally Posted by shmalec
Also academic, but isn't the point of the condensers to evenly illuminate the negative? Even a blank negative should add a fair amount of diffusion to the optical path. I would think that would more or less interfere with any optimization of the condensers to match them to the lens-to-negative distance and projecting lens focal length.
You are thinking of a diffusion head. Condensers produce collimated light in which it is focusing an image of the top of the bulb down toward the lens with most of the rays traveling in the same direction. If the enlarging lens (or the bulb) is not in the correct position then many of the light rays bypass the lens and the effect is dimness. If you put a diffusing screen above the negative, you have now evened out the light so any lens position is OK but it now is much much dimmer because the rays are scattered about.
Originally Posted by Tim Gray
A clear piece of negative film will allow essentially all collimated rays to pass through in their original direction and is not a diffuser.
This was the part I was curious about. While clear film does is clear, it definitely does diffuse the light some. However you are right - not enough to really make a difference.
Originally Posted by ic-racer