I am going to replace the old light source in my Durst 138S with a 5X7 cold light, Aristo D54. B&H quotes them at about $650.00.
Is there a reliable source for a "pre-owned" one that you know of? I am not rushed on this since I am working with other materials as well, but want to start the process of finding one soon. I may just decide to buy a new one.
Tom Potter
I recall printing a badly scratched neg (looked like it had been cleaned with steel wool) for a customer several years ago with my Omega D2. I made test prints with both the condenser and with the Aristo cold light. The degree to which the scratches were suppressed with the cold light was just amazing. I probably used Edwal No-Scratch for both tests as that was the usual practice then.
One should point out what Jim Michael above has alluded to above. Defects including slight scratches and dust in a negative can be very effectively reduced using a diffusion head in the enlarger. This is one of the advantages in using such a head. OTOH that same effect can reduce the fine detail in certain negatives. Whether one chooses diffusion or condenser depends on the effect you are looking for. In either case you should develop a negative for a contrast index that fits your enlarger and the vision you are looking for in the final print.
Nate Potter, Austin TX.
Agree, that sums it up.Originally Posted by Bill_1856
Always use an oversize cold light, larger than the negative you plan to print. This is
because the perimeter the cathode tube doesn't produce even illumination. And be aware that some of the older cold lights can behave flaky. New ones aren't terribly expensive for this size work. I'd check with Aristo, and would specifically recommend the blue-green light for VC paper.
On further reflection, another advantage of diffused light, is that it basically mimics the results of contact printing. You might see that with diffusion light, "what you see is what you get".
I would be interested to read the article which illustrates that both types of light can be used with equal success. Doesn't the Callier effect remove separation, mainly in the dense portions of the negative ? Wouldn't this disproportional effect, amount to the opposite of what we see with compensating developers, which increase separation in the low values ?
No, if one needs the last information from the negative, from the low and high values, one needs a double condenser and a point lamp. Condenser, lamp and lens has to be aligned very carefully. And if the lens can show best resolution wide open, the lens cannot stopped down with point light, one can see all information from the neg on the print. But as mentioned before all scratches and dust particles too.
Point source enlargers are use for microphotographic negatives and in the field of the graphic arts. But with other negs one has a lot of work with spotting.
Peter K
Yes Peter that is my experience. I use a point source condenser head occasionally in my home darkroom. It is a home design with a virtual aperture in front of the halogen bulb so that the degree of contrast can be altered to suit the style of print desired. The idea of course is that all rays from a point light source reach the paper from a single angle (more or less depending on how pointy the source is). Grain is dramatically emphasized as well as any kind of defects. Maximum contrast is achievable to the point of being distasteful due to the almost complete lack of off axis modulation of of tonal values. Contact printing is vaguely analogous in that replication of detail is pretty precise due to the proximity of the neg to the paper but there is a degree of tonal modulation because the normal bulb or cold light head is an extended source.
Another way of looking at it is to consider a point source a large f/no. (meaning small aperture) while an extended source is a small f/no.
Nate Potter, Austin TX.
"I was just re-browsing Fred Picker's 1974 book titled ZONE VI WORKSHOP and read with amusement the apparent frustrations of one of Fred's students, who went to all kinds of trouble in modifying his condenser enlarger in order to produce prints that fit the contrast range of his negatives. He tried diffusion glass in the filter drawer. Then he tried diffusion paper. To no avail."
Also for the record, I was not trying to match the *contrast range* of the negatives - but something a bit more subtle: trying to produce prints which matched my contact prints, which showed un-blocked details in the higher values of the waterfall.
I am delighted to be proven wrong about the Callier Effect, decades later as it were. If someone can explain this nicely, and show some sample images, I will be most grateful.
The images I made back then, with condenser light, displayed an abrupt "shoulder" you might say, while those made with the cold light head, matched the contact prints, under otherwise identical conditions, and continue to do so today.
Re OLder Durst 5/7 Cold light heads: The unit can come in two packets that can slip into the condensor head. Each can be the replacement for the two condensors. Or, one can also put the lamp packet above and condensor in the lower portion of the head. Whether this might produce an intermediate level of diffusion I do not know; or, if it might just broaden the "feather" of the illumination -I do not know. Additionally, there were 3 different types of gas (tubes) made by Aristo Lamps: B/W, VC (B/W), and color back in the olden days of 1950s, 1960.
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