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> Safelight for colour paper |
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#21
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You could also try knocking the setting down a couple of notches. I use Kodak paper from the roll, so it has 2 exposures to the light from the Duka. However having used both Kodak and Fuji paper, I estimate the Kodak paper is at least 1 stop slower than Fuji which will help of course. |
#22
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Colour paper safelighting
In the 1980s I visited the darkrooms in the basement of the Centre Georges Pompidou in the Beaubourg, Paris. After a few minutes of dark-adaptation the level of safelighting, from sodium vapour lamps, appeared startlingly high - they needed it! I have clear memories of the staff hanging 52" wide rolls of colour paper onto a steel wall with magnets and stepladders. The enlarger was, of course, horizontal, on rails.
The sodium lamps emit narrow spectral lines between the green- and red-sensitive emulsion sensitivities. Filters over the lamps hold back the UV. The accompaniment was weird electronic noises from Pierre Boulez' IRCAM school of music down the corridor (he had been conductor of the BBC Symphony Orchestra in the previous decade). Does anyone remember the stacked ball loudspeakers of the era? |
#23
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It would be worth asking your colour paper supplier what is the response spectrum of the emulsion. The problem with LEDs is that, although the emission peaks at a specified wavelength, they usually have a bell-shaped curve with a pronounced 'skirt', which may not be what you are looking for.
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#24
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I had a (very) brief flirtation with colour printing a few years back and tried 590nm LEDs but as I recall, the level had to be so low to avoid fogging, they were of very limited use.
It is possible my LEDs were not very good and were emitting away from their nominal wavelength. They have a narrow bandwidth, but as JO observes, it is not infinitely short and they will emit either side to some degree. The better the quality, the lower those off-centre emissions will be, but will never be as sharp as a discharge lamp like the Duka. Perhaps putting them behind a colour safelight filter will allow brighter light than would be possible with just the filter and a normal lamp, so I would not take my limited experience as gospel. An LED is cheap enough to try - just make sure you get good quality ones and do not over-drive them. Last edited by Bob; 6th May 2021 at 12:31 AM. |
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