"Never mix OC and red safelights in the darkroom"

2F/2F · Sep 30, 2009

I use both. Red is by the developing trays, and is generally the only one I have on, but I also have a 0C light near the enlarger, and I turn it on as needed. I keep both of them a healthy distance of about four feet from the work area, and point the 0C into the wood ceiling instead of directly at the enlarger. The school darkroom where I learned used both as well, unless the whole class was working with litho film, in which case only the red lights would be lit.

Stan160 · Sep 30, 2009

michaelbsc said:
As an aside, it occurred to me that I can put a very small compact fluorescent bulb instead of the recommended 25W incandescent as a heat controlling mechanism. I know the CF bulbs cannot safely be used as white light in the room as they have an afterglow that will fog film and paper. Is that afterglow UV, and will the #1 filter trap that making them safe?

I've got a 3W CFL in a Kodak Beehive light with an OC filter. Results indistinguishable from a 15W incandenscent. Tested to 15 minutes (didn't try any longer) with no fogging on Fomatone or Ilford MGIV.
Ian

dancqu · Sep 30, 2009

VC Paper? Head for Red

As has very likely been mentioned, VC papers are
blue and green sensitive. Graded papers are blue
sensitive only so any good yellow to orange-ish
color will do.

Graded is my choice in part because they afford
a higher level of lighting in the visible spectrum.

VC or Graded, light levels may be increased by
carful handling of the paper. Dan

David A. Goldfarb · Sep 30, 2009

I have a Jobo LED safelight with amber for B&W as well as lights for Agfa and Kodak color neg papers aimed at my developer tray on the wet side and a Thomas safelight with the vents closed all the way on the dry side but also illuminating the wet side, and no problems. I have an arrangement with the dry side set up in a study that I can black out and the wet side in an adjacent bathroom converted for darkroom use.

RalphLambrecht · Sep 30, 2009

michaelbsc said:
Ralph, are you saying that the #1 filter is preferred?...

I find the #1a filter to be insufficient. Yes, I prefer and recommend the #1 filter instead. Kodak recommends #1a only for slow orthochromatic materials and lists #1 for blue-sensitive materials. Common printing papers are blue-sensitive.

michaelbsc said:
...As an aside, it occurred to me that I can put a very small compact fluorescent bulb instead of the recommended 25W incandescent as a heat controlling mechanism. I know the CF bulbs cannot safely be used as white light in the room as they have an afterglow that will fog film and paper. Is that afterglow UV, and will the #1 filter trap that making them safe?...

My safelights come with a 15W recommendation. CFLs are probably OK for safelights. Their disadvantages are not a big issue in that application. Their afterglow is pretty weak. I don't see how that can hurt anything. However, I am sure they got more blue light content than incandescent bulbs. I would do a test to be sure.

RalphLambrecht · Sep 30, 2009

Anon Ymous said:
This paper has it's maximum spectral sensitivity at 550nm and drops to zero at about 575. Any filter that doesn't leak light with wavelengths between 550 and 575 would therefore be safe. Anything from 580nm and over sounds fine, the 610nm filter should be ok, provided that it's sharp enough. In any case, the distance between the paper and the safelight is something to consider. When you double the distance, the maximum allowed time doesn't double, it gets 4x.

The last part of your note is important, because considering wavelength alone will get us in trouble. All safelights transmit some electromagnetic radiation outside their filter spectrum. That's why we test for the maximum time they can protect the paper. For example, a light red filter (#1a) has no transmission below 600 nm, according to the Kodak spec-sheet, but it will fog Ilford MG-IV within a few minutes if the safelight is strong or close enough, despite the MG-IV spec-sheet saying that the paper has almost no sensitivity above 550 nm.

BetterSense · Sep 30, 2009

This is true. When I first made my red LED safelight I thought I could make it as bright as I wanted because it was red, of small linewidth, and the paper wasn't sensitive to those wavelengths according to the datasheet. It would fog paper in seconds; then again it was extremely bright. I turned it down to a sensible brightness and it's utterly safe.

fotch · Sep 30, 2009

Stan160 said:
I've got a 3W CFL in a Kodak Beehive light with an OC filter. Results indistinguishable from a 15W incandenscent. Tested to 15 minutes (didn't try any longer) with no fogging on Fomatone or Ilford MGIV.
Ian

That is suppose to be equal to a 20W, 33% more. I suppose the distance/time can be adjusted to prevent fogging.

Ben Marks · Sep 30, 2009

I'm sure that this has been said above, but you can get drift in any light source over time. Best is to do a simple test at your working distance and twice your working time (including time in trays etc.). My idea would be to leave a coin on a piece of unexposed paper. Cost of the test is minimal. Repeat every 6 months.

Ben Marks

RalphLambrecht · Sep 30, 2009

Ben Marks said:
... My idea would be to leave a coin on a piece of unexposed paper. Cost of the test is minimal. Repeat every 6 months.

Ben Marks

Ben

This test is unreliable. Just change it slightly to

'leave a coin on a piece of exposed paper'

to make it more valuable. Actually, I would leave several coins and take them off after 2, 4, 8, 16 and 32 minutes to get an idea how long the safelight is good for.

2F/2F · Sep 30, 2009

I'm sorry to hijack, but I have a wee question that has nagged me for some time.

I always thought that 0C was a zero and a C. Others seem to write it and speak it as the letter O and a C.

Which is correct?

RalphLambrecht · Sep 30, 2009

2F/2F said:
I'm sorry to hijack, but I have a wee question that has nagged me for some time.

I always thought that 0C was a zero and a C. Others seem to write it and speak it as the letter O and a C.

Which is correct?

Unfortunately, I don't know what the 'O' stands for (ortho?), but Kodak's literature makes a clear typographic difference between the 'O' in OA and OC filters versus the '0' in 00 or #10 safelight filters.

john_s · Oct 1, 2009

The spectrum of leds (most if not all) is quite wide. I made a safelight with amber leds and it was not safe with mainstream papers (Ilford MC, Agfa MCC). Look at the led in its refection from the underside of a CD at the angle that shows the "rainbow" effect. You might be surprised to see some yellow, green and even aqua. I ameliorated it with a sheet of Rubylith, easily obtainable at graphic arts suppliers. My next led safelight was *very* red and can be quite bright as well as really safe.

Incidentally, I have read that the spectrum of leds is narrower at lower currents, so it makes sense to make a very bright safelight and fit a variable resistor as a dimmer.

clayne · Oct 5, 2009

Stan160 said:
I've got a 3W CFL in a Kodak Beehive light with an OC filter. Results indistinguishable from a 15W incandenscent. Tested to 15 minutes (didn't try any longer) with no fogging on Fomatone or Ilford MGIV.
Ian

Same here. I picked up a 6W red CFL from Home Depot and installed it in a Premier housing - pointing upwards to bounce off the ceiling. It's atleast 12 ft away from the trays and 8 ft from the enlarger. No fogging, ever.

I like it a lot as it's bright enough to work in. I don't have any issues working in red lighting, personally.

BetterSense · Oct 5, 2009

I tested my amber LED and found it safe only for certain values of 'safe'. The red LED was safe to ten minutes even at a rather bright level so I guess I'll take bright red over dim amber.

I tested by flashing the paper 1s at f/22, then laying a coin on it for ten minutes, and developing. Even then the coin shadow didn't appear until I flashed the paper again while it was in the developer. Make sure you test exposed paper when you test a safelight!

mike c · Oct 5, 2009

2F/2F said:
I'm sorry to hijack, but I have a wee question that has nagged me for some time.

I always thought that 0C was a zero and a C. Others seem to write it and speak it as the letter O and a C.

Which is correct?

Ive all ways thought OC stood for Ortho Chromatic,seems ok to me.

RalphLambrecht · Oct 5, 2009

mike c said:
Ive all ways thought OC stood for Ortho Chromatic,seems ok to me.

My research into the memories of Kodak retirees came up blank. Nobody seems to remember anymore what the 'O' in OA or OC stands for, but they ruled 'ortho' as a candidate out, reasoning that other filters are more ortho than these and don't have the letter 'O' in them.

I afraid the answer is buried at the bottom of the Rochester dump.

"Never mix OC and red safelights in the darkroom"

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