Enlarger bulb workaround
I've been struggling for a couple of days now with a particularly dense negative which needs a little burning too. But since my base exposure was almost three minutes, I tend to get bored when it comes to burning in two more stops on the bright bit at the bottom and so on - and that is with the aperture wide open! I'm beginning to think that my lightbulb is about at the end of its life - but finding a replacement 240V 300W bulb for a Durst L138S is not easy. :(
So in a flash of inspiration I decided to try something really different: I bought a 15W low-energy bulb! Screwed it in the socket, turned it on, adjusted the placement a bit, and suddenly I had a full stop more light. Then I realised that this is essentially "cold light", and removed the heat filter: Another stop!
And then I messed around with lenses a little, and ended up swapping the 150mm with a 180mm, and the 200 condenser with a 240. The result was surprising, to say the least: More even illumination, and yet another stop more light. I would have thought the illumination would decrease, since the condensors illuminate the whole 5x7" and not just the 4x5" I was printing, but there's no arguing with the EM-10?
The drawback is the long warm-up time of the low-energy lamp, but since I had exposure times in the minutes anyway I can use a lens cap to start and stop exposure. After all, the 15W "bulb" isn't going to heat the negative much in 10 minutes, compared to what the old 300W bulb did...
Five green stars to you Ole :-) Knew it could be done
Sounds great. I see a Metrolux in your future.
A company here in Italy is running ads for bulbs that are instant on. I've seen one and it's much faster then normal bulbs. Might not be instant but good enough I think.
A 15 watt bulb out did the 300w? Must have been nothing but heat out of the big bulb.
We have bulbs in our apartment that are "instant on," but they still have some ramp time until they stabilize.
Sometimes, "instant" is a relative term.
The one I saw visually had no delay. Not that means much. But I figure if you're looking at 30 second exposure any delay will be a non-issue.
3 mins exposure even with a 300W bulb! Sounds like those negs need the equivalent of a thermic lance or small controlled nuclear explosion. Both have great light outputs but read the safety instructions carefully!
Maybe you could leave the bulb permanently on and fit a shutter to your enlarging lens?
Which is the cold cathode solution?
Originally Posted by BarryWilkinson
Tungsten filament lamps convert about 95% of the electrical energy directly to heat, so don't be surprised at the higher output of the fluorescent lamp.