Source for 660nm red LED bulbs?

[Marco Buonocore]

Does anyone know a source for 660nm red LED bulbs for use as a safelight?

I'm trying to overhaul the safelighting in a large group darkroom. We've tried the E27 red LED from Superbright bulbs (https://www.superbrightleds.com/moreinfo/led-globe/2-watt-g11-globe-bulb-360-degree/440/#/tab/Specifications), but I got fogging on Ilford Classic after a few minutes.

Kodak had a short lived LED safelight, and it was 660nm; that's what I'd like to aim for.

All the stuff I'm finding is used for hydroponic grow ops, and I suspect is too bright.

Thanks!

 

[Nodda Duma]

Aim your LED into a cardboard box with the inside spray-painted a uniform medium-to-dark gray. Cut a 2-4" diameter port on the side, and put a piece of painted cardboard in to block a direct path between the LED and the port.

Cheap light reducing filter (like an ND filter), plus the light coming from the output port is uniform to 10% variation or less.

Or just get a 3W 660nm LED and LED driver off ebay.

 

[Photo Engineer]

Try Radio Shack.

 

[ritternathan]

try

http://www.amazon.com/Feit-Electric...&keywords=Feit+Electric+A19/R/LED+A19+Red+LED

It is not 660 but it works in my darkroom as long as it's placed 5 feet or more away from trays. Very bright.

 

[Ken Nadvornick]

Try observing the red light emitted from your Superbright LED bulbs as it reflects off the surface of a recorded CD or DVD disc. Do this in a totally dark room so that no other light sources contribute.

Look for small slivers of non-red light. Often these will appear to be faint blue or green bands of color buried in a sea of red. If you see any at all, then interpose a small piece of Rubylith between the CD/DVD and your eyes. The slivers will disappear while the red light will not be noticeably diminished.

I have been advised by an engineer who works with LEDs that these slivers of non-red light can be one result of the intentional introduction of various dopant compounds during the LED manufacturing process. The colors they help produce are visually lost in the overwhelming pure red, but are not invisible to b&w photo papers and can easily cause fogging across normal darkroom working time frames.

In my case I directly observed both faint blue and faint green bands of light coming from my unfiltered 635nm OptiLED bulbs. So I created a small "housing" for my six LED bulbs made from Rubylith.

Using the naked bulbs my (pre-flashed) paper fog tests showed noticeable degradation over several minutes. After placing the LEDs under the Rubylith housing, a retest showed no fogging whatsoever out to a full 60 minutes, at which point I intentionally terminated the test. This was with fresh Ilford MGIV, both FB and RC.

Simple Rubylith filtering might be worth a try before spending on new LEDs that may or may not have similar issues.

Ken

 

[tokam]

Not to hijack the thread but while we're on the colour of safe-lights for black and white darkroom work I have never used red safe-lighting. From 1974 when I started printing on single grade papers I always used a yellow/green Philips safelight bulb which I placed in the overhead socket on the laundry ceiling. No problems with fogging of paper as far as I could see.

This colour bulb was recommended to me when I bought my first enlarger and other darkroom pieces. I do remember the sales assistant saying that red safe-lights were 'old hat' and not suitable for modern materials - in 1974!!

I'll try and dig out the bulb to give you the model / colour description. I haven't printed in a few years, (will have to sort that situation out), but would this bulb be suitable for multi-grade papers or is the traditional red safelighting the way to go?

 

[Ken Nadvornick]

Traditional red is the way to go for maximum safety when using multi-grade, because the MG paper is sensitive to both green light (soft contrast) and blue light (hard contrast).

That's how my additive variable-contrast b&w enlarger head works. It has both a blue and a separate green light source, which when mixed together in varying proportions results in varying paper contrast levels.

Any safelight that had a green component, whether intentional like your Philips bulb or unintentional like a green spike in a red LED, would upset that system entirely.

Also, some graded papers (Slavich Unibrom, for one) specifically state the requirement to use only red. I occasionally use this paper in my own darkroom.

Ken

 

[Neal]

Hi Marco,

https://www.superbrightleds.com/mor...-angle-1300-mcd/284/1211/#/tab/Specifications

http://www.ledsupply.com/deep-red-high-power-leds

Some helpful APUG member posted his successful use of Rosco gel filters. I rejuvenated two old fashioned safelights with one of their filters, some spray contact cement, the existing but faded filters, and some instant-on CFLs. They work perfectly. Look here to choose the appropriate filter.

Good luck,

Neal Wydra

 

[Marco Buonocore]

Thanks for the advice, guys.

Ken, I appreciate your method of testing the LEDs. That's a sound approach.

Neal, thank you for those links, I'll pass those on to our facilities coordinator. Screw bulbs would be ideal, but at this point I'm asking for a lot!

Because we're in a shared darkroom, people are using all sorts of papers. So deep red is the best solution. It's a big space too - the sink is probably 18 feet x 5 feet at least. I'd like to avoid using filters (we have a roll of rubylith), because filters need changing and that's something historically we've not been very good at doing in this darkroom. I guess filters underneath LED lights would need changing less often, as there is less heat generated. I think they would be a last resort.

 

[RalphLambrecht]

Does anyone know a source for 660nm red LED bulbs for use as a safelight?

I'm trying to overhaul the safelighting in a large group darkroom. We've tried the E27 red LED from Superbright bulbs (https://www.superbrightleds.com/moreinfo/led-globe/2-watt-g11-globe-bulb-360-degree/440/#/tab/Specifications), but I got fogging on Ilford Classic after a few minutes.

Kodak had a short lived LED safelight, and it was 660nm; that's what I'd like to aim for.

All the stuff I'm finding is used for hydroponic grow ops, and I suspect is too bright.

Thanks!

Do not assume these LEDs are free of fogging just because they emit a wavelength outside of the paper's spectral sensitivity.That would make sense but, It ain't sften ,they ae bright enough to fog the paper anyway.A safelight test is always recommended.dimmer is safer than redder.

 

[john_s]

...dimmer is safer than redder.

Quite so. But very red can enable a brighter ambient illumination. One great thing about making your own LED safelight is that it's easy to make up several units, each with its own variable resistor. I have several quite bright very red lights. (one is older non-safe LEDs made safe with Rubylith) I have in addition to general lights a couple on the wall behind me (one to the left and one to the right) at a height a little above the easel: this doesn't illuminate the paper much because of the shallow angle, but it does enable me to easilyfind my bits and pieces around the enlarger. Over the wet end of this tiny darkroom I can temporarily turn on an orange LED lamp to see how the development is going: after the very red, the orange is a revelation!

The very red LEDs were chosen from the rs-components web site,and I have an array of about 60 of them mounted several mm above a bit of circuit board so they could be bent at angles to widen the illumination, and a bendable aluminium reflector behind to modify where the light goes.

Reflecting the light off wall and ceiling reduces the intensity compared to directly shining on the paper. I admit that the very red isn't easy on the eyes, hence my short duration orange one where it's most needed, to look at paper development.