Using a OA safelight filter in a darkroom with OC filters????

[bigdog]

... I and many others use. Not just any LED, a specific one.

https://www.superbrightleds.com/more...60-degree/440/

https://www.superbrightleds.com/more...Specifications

Randy, what color bulb do you suggest? Your links don't show me the specific color. Or are you saying to use the white bulbs in the safelight housings?

Not to scoop Randy, but I am one of the "others" he mentions. It's the red one. I have tested it with Ilford Multigrade paper (using the Kodak method) and it tested "safe" to 10 minutes. It may be good longer, but I did not test longer than that.

I had long been a sceptic of red led bulbs for safelights, but a number of reliable people swore by this particular bulb, and they are cheap so I bought a couple, did the proper tests, and was pleasantly surprised. I have a combination of these bulbs and conventional safelights with OC filters in my darkroom.

Regardless of what one uses, proper testing is paramount!

[Tin Can]

This thread is a nice example of responses with reliable and detailed information. Randy, what color bulb do you suggest? Your links don't show me the specific color. Or are you saying to use the white bulbs in the safelight housings?

Yes Red. Everybody should look at the second link and examine the spectrum of these bulbs. That's how I found this bulb. I may have been the first to recommend this RED LED and only this exact bulb. I have tried many others and they are no good for our purposes.

Of course test yourself.

I have 6 of them in my roomy darkroom and cut X-Ray in relatively bright light. I have one 30" over my paper trays and have no issues.

[David Lobato]

Thanks.

[Tin Can]

Sorry Bogdan and guys. I feel I have written about this bulb so many times on this forum I thought by now most are aware of it. I am well aware I post too much.

I know I suggested this bulb some time ago to OP and he was not responsive.

Also many try OTHER Led and have a bad experience.

[Michael R]

The Kodak safelight test linked by Doremus (Ilford is the same) is THE safe time test to do as it accounts for the cumulative exposure of safelight and enlarger. The results can be surprising.

There is no such thing as a safelight that is 100% safe. It is simply a matter of how much safe time you get.

It will depend on the paper - an important variable. I would caution OP to do a proper safe time test with this bulb from SuperBright. While the peak output at 635nm is "ok" (higher would be better), output extends well below that wavelength. Also note typical of red LEDs, there are small amounts of output in the green and blue wavelengths - exactly where you don't want any output. It may or may not cause issues depending on the paper, brightness, and the length of safe time you require, but always test first.

[Tin Can]

I always limit any sensitive materials to the shortest possible exposure to any safelight.

The mention of enlargers is somewhat secondary, but most produce a lot of stray light.

Which come from the traditional Hot Head with heat producing bulbs requiring cooling.

But LED enlarger Heads are another topic.

[Michael R]

Sorry I should have been clearer regarding enlarger exposure. I'm referring to the combined effect of image exposure and all non-image exposure. Even under the ideal scenario with zero light leakage from the enlarger, the safe time is still dependent on the cumulative effects of image exposure and safelight exposure. That is why the Kodak/Ilford test is informative.

[Bill Burk]

I looked at the graphs of the OA and OC filters and notice the difference seems to be that OC cuts about 20 NM more out of the green. When I thought about variable contrast paper using blue and green light, it suddenly made sense to me that the OC filter which cuts more green would be safer than the OA which is suited to older material.

[Doremus Scudder]

I looked at the graphs of the OA and OC filters and notice the difference seems to be that OC cuts about 20 NM more out of the green. When I thought about variable contrast paper using blue and green light, it suddenly made sense to me that the OC filter which cuts more green would be safer than the OA which is suited to older material.

Hey Bill,

Where did you find the spectral graphs for the safelight filters? Is there an online source? I'd sure like to take a look at them.

Best,

Doremus

[Michael R]

Doremus - see link:

http://www.kodak.com/global/en/profe...845/ti0845.pdf

There is also some info here: (but the link above is more comprehensive)

http://motion.kodak.com/US/en/motion...ts/default.htm