Substitute enlarger globe?

[Janos]

Happy new year to all- I'm new to this forum but am enjoying it immensely.
Question: Does anyone have any thoughts on the idea of using one of those LED lamps, 12v which come in the same exact chape as the dichroic halogen lamp 100 W, which is currently in my Durst M801 colour head enlarger.
As they are available in warm white, I imagine that VC filters won't need too much ofr a tweak, and everything will run much cooler,- perhaps more consistently too.
Any thoughts on this would be welcome, but I'm going to try it anyway.
Thanks.

 

[RalphLambrecht]

Happy new year to all- I'm new to this forum but am enjoying it immensely.
Question: Does anyone have any thoughts on the idea of using one of those LED lamps, 12v which come in the same exact chape as the dichroic halogen lamp 100 W, which is currently in my Durst M801 colour head enlarger.
As they are available in warm white, I imagine that VC filters won't need too much ofr a tweak, and everything will run much cooler,- perhaps more consistently too.
Any thoughts on this would be welcome, but I'm going to try it anyway.
Thanks.

It's always worth a try, but I suspect it won't work for several reasons. First, they are probably not strong enough. Second, will depend on their spectral distribution. Some LEDs achieve white light by combining multiple LED sources (several narrow wavelengths across the visible spectrum), which can create strange spectral distribution patterns, especially if combined with VC filters. The linked article goes into more depth.

http://physics.nist.gov/Divisions/Div844/facilities/photo/Publications/OhnoOE44-2005.pdf

 

[bdial]

I use MR-16 12v LED lamps in my home office lighting. They don't produce light that's remotely close to what a 100 W bulb does in brightness.
As a guess, you'd give up at least three stops, maybe more through the filters.

 

[ic-racer]

Why?? Are halogens getting hard to find in Australia?

 

[Janos]

Why?? Are halogens getting hard to find in Australia?

Thanks for your responses, guys- I'll have a look at that link in a mo. No, you can get them, but a 100 watter is a bit harder. Mainly the light box gets pretty hot after a while. Even so, exposures are a bit too long with bigger enlagements, especially as I try to use f8.

 

[Marco B]

Question: Does anyone have any thoughts on the idea of using one of those LED lamps, 12v which come in the same exact chape as the dichroic halogen lamp 100 W, which is currently in my Durst M801 colour head enlarger.

There are actually two types of "white light" LED's:

- The ones Ralph described using three LEDs with the primary colors red, green and blue that mix up to something close to white.
- Blue LEDs covered with phosphorescent material to achieve white light

Be aware that the latter type can have, like fluorescent tubes, a very long after-glow. I recently bought a 1W "household" LED based bulb, consisting of maybe 24 individual LEDs using phosphor. I was surprised how long and strong the after-glow was. I also noticed there was actually quite a big difference between the individual LEDs. I don't know what causes the inconsistencies.

See also:
http://en.wikipedia.org/wiki/Light-emitting_diode

Marco

 

[Bob-D659]

You have to watch the ANSI sub codes on halogen bulbs closely. The ELC 250 watt 24 volt ones come in several subtypes with different light outputs, see the Ushio bulb specs here Dead Link Removed . An ELB puts out almost the same light as a long life ELC and only uses 80 watss of power compared to 250 watts!

If you have a 100 watt bulb with a 1000 or 1500 hour rated life, it will put out a lot less light than a 50 hour rated bulb.

 

[ic-racer]

I have never seen a 12V MR-16 Led that puts out 100W. More like 5 to 20 w.