Use Thomas Safelight or not

I like my Thomas safelight, but my current darkroom is too small to use it safely and it isn't really necessary in a small space, so I use two LED safelights (Jobo Maxilux Color), one for the room and one closer to the trays.

One thing to be aware of is that it doesn't work to plug it into your timer and turn it off for focusing the enlarger, because of the long ramp time before it reaches a steady brightness. I suspect there are people who do that, but generally you want to turn it on and leave it on while working so that it gives a consistent output.

~andi said:

With red LED you can go very very bright without fogging. I sold all safelights I have been using and now use a single Heiland LED safelight at full power. I can read the newspaper easy everywhere. Its like night and day compared to the incandescent red or green/yellow bulbs and Paterson safelight i used before. I prefer amber lights or yellow/green to red but the brightness levels these red LEDs provide convinced me and I've not regretted it ever since (skip to 4m11s for a comparison):



Andi

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Wow really cool. I wonder if the LEDs are RGB and use PWM to dim and change the color?

Greg Davis said:

My post from another thread:

To continue this thread, I took apart my filters and looked inside to see what gels are used. They are as follows:

Yellow tape:
White vellum diffusion
Roscosun CTO #3406
Roscosun 85 N.6 #3407

Red tape:
White vellum diffusion
Rosco Fire #19 (two sheets)

Black tape:
White vellum diffusion
Roscosun CTO #3407
Roscosun 85 N.6 #3406 (four sheets)
Roscosun CTO #3407 (again)
White vellum diffusion

The manufacturer cut the sheets in such a way that the gel numbers were still on the edges.

I also have an old filter from Thomas Duplex that I am unsure of its purpose since the tape has been replaced, but it had an amber filter like a 3407 and 3406 combined, a dark green filter like a Wratten #58 with two diffusion sheets between them.

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Mr. Davis,

I was wondering if you could confirm the filters I found:

#3406:
https://www.bhphotovideo.com/c/product/44195-REG/Rosco_101034062024_3406_Filter_RoscoSun.html

#3407:
https://www.bhphotovideo.com/c/product/44198-REG/Rosco_RS340711_3407_Filter_RoscoSun.html

#19:
https://www.bhphotovideo.com/c/product/43899-REG/Rosco_RS1911_19_Filter_Fire.html

White Diffusion:
https://www.bhphotovideo.com/c/product/44042-REG/Rosco_RS302611_3026_Filter_Tough.html

I could not find a White Vellum Diffusion, so I picked the closest thing I could find.

claudio

Mainecoonmaniac said:

Wow really cool. I wonder if the LEDs are RGB and use PWM to dim and change the color?

Click to expand...

I guess they're using PWM, at least its a fair bet and it makes sense maintaining color temperature. The safelight has a small switch mode power supply integrated in the mains plug (12V DC), then there's a wire to a very small and light box containing the dimmer an 3-way rocker switch (red-off-white) and about 2m of wire to the lamp housing itself. it has a white frosted "half-pipe" above two LED strips which makes it look like a CFL.

The LED strips are: 57 smd soldered red LEDs and a second strip with 57 smd soldered white LEDs (they're looking yellow, so I guess they're blue LEDs with yellow coating). the LEDs are interleaved with resistors. other than that there's no electronics within the tube.

I checked the spectrum of the red through a prism and did the CD-reflection test. there's a very very tiny amount of very dark green that's emitted as well. its extremely weak and i guess of no consequence.

I aborted the safelight test with ilford fb classic paper after 15 minutes without any change at the closest position the paper is going to be (about 1,75m away).


Andi