Gast
Hi lads,
To get straight to the point, I’ve got an opal lamp with a condenser.
I’m looking for a true point light source for my Durst 138.
The reason is the grain structure in the print, which gives it a quality all of its own.
I currently have a test setup with Limiled Luxeon V LEDs in royal blue and green (through the Durst condensers), whereby the blue one is already delivering excellent results (so this business about it having its own quality isn’t just some ‘I imagine it to be like that’ nonsense, but verifiable. e.g. approx. 20x enlargement Minox on 18x24 finally produces no more “grain-free sharp” mush from the Effke 25 A49, but almost a halftone effect).
The problem is simply that this only works with blue, i.e. hard light, as the green LEDs are on the outside and are much dimmer (or less effective, by about 6 stops, despite a 2:1 ratio).
So I’m looking for a light source that’s similarly small (max. 2x2mm illuminated area) but also provides enough green (if necessary, I’ll just filter it again), as I’ve now got so used to the Variokontrast papers that I wouldn’t want to be without them.
I’d also welcome any practical experience with DIY solutions.
Regards
Martin
dl8ram
Hi Max,
I thought you might still be waiting for a reply.
Osram makes LEDs that combine the three primary colours in a single housing.
By adjusting the brightness, you can cover the entire spectrum.
Best regards,
Alois
Wolfgg
Has anyone ever looked into how much effort and expense is involved in fitting gas-discharge lamps into car headlights?
Regards, Wolfgang
Claudius
The three-colour LEDs Max mentioned are by no means capable of covering the entire spectrum; they can only produce various mixtures of three fairly narrow-band colours.
Whilst this may fool the human eye—which simply cannot distinguish a ‘mixed colour’ from a true colour—it is a completely different matter when it comes to photographic paper.
dl8ram
Hello,
I haven’t tried it yet. I’m just passing on what I was told at Osram Semi.
Best regards,
Alois
Claudius
Either they’ve been telling you nonsense, or they’ve expressed themselves very unclearly.
LEDs are non-tunable, narrow-band monochromatic light sources; RGB LEDs simply consist of three of them. This means that all possible mixed colours can be achieved, but the spectrum remains unchanged, consisting of three bands with, at most, varying amplitudes.
Incidentally, the light emitted by ‘white’ LEDs consists of only two bands: blue and yellow (not the mixed colour, but actually the spectral colour).
dl8ram
Hi Claudius,
You're absolutely right!
Best wishes, Alois
MirkoBoeddecker
Martin,
There’s a Beseler spot light source currently on sale on eBay.
Best regards,
Mirko
Gast
Found it,
Thanks for pointing that out, Mirko.
Best regards
Martin
MirkoBoeddecker
Martin,
I forgot to mention: ask the seller about the light bulb and find out if it’s still available.
These light sources date from before our time, and a lot of stuff from the 70s and 80s no longer works today because the bulbs are no longer available.
Best regards,
Mirko
