led enlarger color

[claudius]

hi,
when you convert your enlarger to LED light, what color do you use ??

my durst bwl 300 has two 1000w halogen tubes wich are around 3000 Kelvin in color.
this is quite yellow , ad could be rather dark for large enlargements to fous when the nega is dense.

the led beads comes in soft white with 3000 Kelvin and cool white with 6000 Kelvin.
the emitted light is the same, but the soft with 3000 K is preicely the same as the original Halogen tubes.

what impact will either of them have on the print ?
klaus

 

[claudius]

forgot to mention, it is only for B&W printing.
klaus

 

[DREW WILEY]

You want blue and green, as pure as possible, and independently controlled. A separate brighter white source might be convenient for focus and composition. Of course, going full tri-color RGB will theoretically produce white; but you probably won't achieve a color enlarger this way due to the adolescent stage of LED technology at the moment. Working with VC papers might be realistic if the prints aren't too big. For sheer muscle you'll have to go halogen. I have a very powerful blue-green 12x12 cold light, but doubt this is made anymore.

 

[LouisGR]

Colour temperature is important with multigrade B&W printing.

My kit is a Focomat 1c and the Heiland Splitgrade system in manual mode with Agfa Gr 0 and 5 filters. I changed from Philips Photocrescenta 75W type PF 603 E51-P3/3 (phew!) incandescent lamps to a LED about 18 months back. I chose a 10W OSRAM warm-white LED lamp. According to the manufacturer, the colour temperature is 2700 degrees K, and the 10 W LED is equivalent to 60 W incandescent. The colour temperature of the Philips lamp is 2800 degrees K. The OSRAM bulb is virtually the same size and shape as the Philips and fits well.

My first prints were well-exposed, but the grading was too soft. After a round of trial and error calibration I have settled on giving 1.8 to 2 stops extra exposure with the Gr 5 filter, leaving the Gr 0 filter timing unchanged from the Heiland module reading [you can simply dial this into the module in steps of a tenth of an f stops].

This works very well and produces very nice prints. And the enlarger stays cool.

I hope this is useful.

Cheers

Louis

 

[RalphLambrecht]

forgot to mention, it is only for B&W printing.
klaus

contact Heiland electronics in Germany.They do this as a custom conversion for all types of enlargers.

 

[claudius]

thank you all.
i have decided to try the bright white led lamps, i did a converson on another enlarger some years ago with the bright lamps.
it worked ok but i noticed that the prints needed less exposure compared to the candescent lamps.
i metered both lamp types. the difference was around 2 -3 steps.
i ordered two 240 volt 100w led on printed circuit with emitters in a row at the same size as the two halo lamps original installed in the light head.
these are to be installed with heat sinks, cooled by seprate 240 volt PC cooling fans.
it all fits in place of the halogen lamps and holders.
no need for the blower and the transformer.
klaus