diffusor enlarger versus condensor

[Donald Miller]

I use glass only. As a further consideration, glass is not simply glass. For instance there is Shott glass available for the Durst neg carriers. Not only Shott glass but also Shott glass with both coating as an option and also with AR as another choice. The price of these goes up quite a bit from ordinary glass.

The green cast of ordinary glass will absorb as much as 40 cc magenta and this will affect the contrast of a print.

Yes, all condenser systems are not the same. Devere (professional grade enlargers) have probably the best design and quality of condensers followed by those in a Durst (professional grade equipment).

I think that all of these considerations affect the judgements that some people make of diffusion versus condenser enlargers.

I can not over emphasize the importance of the light source when used with a condenser enlarger. A point light source makes a massive difference in the sharpness and local contrast in a print.

 

[Donald Miller]

It is worth noting however that a dust particle that is sitting above the film allows diffused light to pass under it from the side (both because of its shape and because of the thickness of the film base), hence reducing it's ability to block light and therefore cast a shadow on the paper. The image forming silver however is in the emulsion, and far "shorter" than a dust particle, so non-perpendicular light will have a lesser effect. The idea that diffused light sources make dust less apparent, so therefore must cause loss of image sharpness is I think, flawed because of this.

How much effect diffused light does have, I have no idea: I'm sure there must be some, but how much, is open to debate. The fact that some see a difference and others do not suggests that any difference is slight. No doubt enlargement ratio is also a factor with small format printers seeing a greater difference because of the greater multiplication factor when going from a small negative to a large print.

I wonder if anyone has done a serious study of these effects?

Cheers, Bob.

I don't know what qualifies as a serious study, but I will say that having printed on everything from a cold light head to a point light source and viewing the prints that I have obtained from each indicates to me that there is a major difference in sharpness and local contrast. Based upon this I would say that your reasoning sofar as the dust beiing above the film and it's effect is flawed. Your reasoning is not taking into account the effects of depth of focus as an enlarger lens is stopped down in considering the location of dust on film.

Collimated light can be diffused however diffused light can not be collimated without passing it through a condenser optical system. The perpendicular and aligned beams of light in a condenser enlarger pass through the film in a totally different manner than the scattered beams of a diffuse light source.

Having said that, each person should use what they wish. I have made my decision based upon what I want from a print.

 

[Bob F.]

Good point: I had overlooked that the dust is likely be in reasonable focus at the same time as the grain. The idea did rather depend on sharp focus only on the grain. Ho hum: another great theory bites the... erm... dust...

Cheers, Bob.