John, The Callier Effect is a real phenomenon written up in photography texts since before I was born (which wasn't yesterday). The essential aspect of it is that the scattering it describes is from the solid grains of silver in b&w emulsions. The dyes in colour films are transparent (except to the wavelengths that they filter) and shouldn't cause an increase to diffusion over what is already present. That means that the relationship of transmitted light to film density won't exhibit the delinearising tonal distortions characteristic of the Callier effect on silver grains.
In my career I've used focusing point source enlargers, cold cathode enlargers, diffusion enlargers, diffusion/condensor enlargers, and additive mini-printers to print from 10in x 10in down to 110 negs. I've used enlargers by Durst, Omega/Chromega, Wild, DeVere, IFF, Rolleimat, LPL, Leitz, Meopta, Beseler, a point source microfilm enlarger that may have been a Kodak IIRC, and a San Marco mini-printer. Except for the point source and the cold cathode enlargers I printed colour and b&w with every other type of enlarger. From enlarger to enlarger there was little difference WRT the appearence of colour prints that they produced. So, why do you get such a difference between your colour prints from condensor and diffuser enlargers? After mulling over your observations for a while, I've come up with this 'short' list <vbg> of what might be happening in your darkroom. Not all of these factors necessarily apply to your case, but without knowing your setup I can't eliminate any, either. Your flare mitigation measures may not be as effective as you hoped. In fact the extra lining inside the bellows is most likely counter-productive i.e. it causes an ~increase~ in flare because it brings the inner surfaces closer to the image path thus more likely to catch stray light. You are unlikely to improve on the flare suppression of a cloth bellows so I consider that to be a mistake. My practical experience is that the most flare free printing occurs when the enlarger format is bigger than the film format being printed. The oversized bellows in that instance keeps the inner surfaces well clear of the image gathering coverage of the enlarging lens. It's also worth noting that the most contrasty enlarger with which I printed in colour was my old Rolleimat, yet it's diffusion box was nothing special. What made the difference was that my lens had a smaller than Leica thread mount, and was mounted on a conical adapter. The adapter had a secondary benefit of acting as a lens hood, and its location above the lens was analogous to the lens hood being in front of a camera's lens. IOW, the flaring surfaces of the focusing tube were hidden from the lens's view (an 80mm Componon, so not too shabby in its own regard). BTW even the best lenses can get hazy after a while in a darkroom, I've seen Componons, Rodagons and Leitzs all brought down by chemical haze that required a CLA. A plain black surface struck by light isn't as dark as a completely unlit surface. An untextured "black" surface may be effective in suppressing the reflection of nearly perpendicular rays, but when the rays are very oblique heavy texturing is needed for really effective flare suppression. That is why the mirror box of many cameras, and the inside of many extension tubes, is ribbed. In the 1970s Fuji coated the mirror box of some Fujicas with black flocking, which was reported to significantly reduce flare. Velvet could be problematic because its light-catching quality is directional, i.e. from one direction it looks jet black but from the other it looks shiny. Diffusion enlarged prints should never have soft focus or fuzzy grain. As the grain is the smallest detail that will be visible in a print, when that is sharp then the image itself will be as sharp as it can possibly be. If your diffusion printed samples lack sharpness then your problem is not the choice of lamphouse. But the differences between condensor and diffusion lamphouses extend to more than just the quality of illumination. Condensor lamphouses mostly use opal lamps that run directly from ordinary electrical outlets. OTOH, diffusion lamphouses mostly are powered by step-down transformers or voltage stabilizers (or both). If you have one of these and it is on your enlarger bench then it's very likely you're getting vibrations that are too small to feel, but are enough to spoil your print sharpness. Some colour heads also have internal cooling fans and these have been known to get out of balance, and induce vibrations. A condensor lamphouse is usually much brighter than a diffusion lamphouse. If, to maintain a constant exposure time, you print at a larger than ideal aperture when using the diffusion head you could get a contrast and sharpness difference. If OTOH you maintain the same aperture and adjust the time (usually an increase) your print can be exposed to more possibility of light spill from the enlarger or light leakage into the darkroom. If the white lights in your darkroom are flourescent, or you have a flourescent light box nearby, the residual UV emissions from them, after they are switched off and appear to be dark, will accumulate more fog on the diffusion enlarged print simply because it would be out in the open for a longer time. Any fogging will lower the contrast and contribute to an appearance of unsharpness. Now if this all sounds like too much speculation over possibly inconsequential influences, and that a good slash from Occam's Razor is called for, just remember that it's photography we're discussing here. The one truth I've found that precedes all others is that every influence goes into the result. IOW the thing you overlook will be the thing that turns around and bites you on the bum :-) regards, Anthony Farr ----- Original Message ----- From: "John Munro" <[EMAIL PROTECTED]> (earlier message snipped) > > I have to hand it to you, Anthony, you made me rush out to my darkroom > to see if I can understand what you said. > > First off, my enlarger has a fabric bellows below the negative stage. I > installed a back-up fabric bellows which I lined the insides of with > black velvet. I also lined the top and bottom sides of the negative > carrier with black velvet - plus I applied a new coat of Kodak flat > black paint to the negative carrier's edges around the image aperture. > I also installed black velvet to line the area above the negative > carrier inside the enlarger. I also lined the lens carrier's > inside-the-enlarger section with black velvet. Last and not least, I > gently cleaned my 90mm Schneider Apo-Componon enlarging lens (definitely > a superior, better than first-class lens). > > Anthony (thanks to you), THERE ARE NOW NO REFLECTIVE SURFACES INSIDE > THIS ENLARGER ABOVE AND BELOW THE NEGATIVE STAGE! > > Next I made prints. Gosh, Anthony, there's no difference in the prints > I made last night from the prints I made a few days ago. Condenser > prints have more apparent sharpness and definitely more contrast than > diffusion color head prints - when I say "more contrast", if color > papers were graded I'd say "more contrast" would equivacate to the black > and white paper grades of about one grade more contrast. The color head > prints have more hues in the color scale range - especially in the > highlights. > > To my seeing the Callier Effect is the same for color materials as it is > for black and white ones - that is the practical reality in my darkroom. > What you've said about color materials not having the same light > transmission properties as black and white silver materials may very > well be, but my printing efforts suggest the Callier Effect is alive and > well for color negatives and positives. > > Hope you're having a GREAT photo day in WONDERFUL down-under-land (or is > it up-over-land?)!!! > >
