Sodium safelight for RA-4 printing in trays?

[skystrick]

I am doing RA-4 printing from color neg and developing in open trays like B&W. I have always done this in total darkness, but I've been reading on here about the possibility of low-pressure sodium safelights like the Thomas and the Osram Duka 10. I hate fumbling around in the dark; is it "safe" to use one of these type of safelights with open-tray color printing?

It'd also be cool to watch the images develop, like I can with B&W under my OC safelight.

Thanks!


P.S. - should mention this is a very small home darkroom, 5 or 6 feet square, with 8' ceiling.

 

[clayne]

It is safe to use the Thomas but you need the color printing specific filters.

 

[Roger Cole]

I printed a lot of RA4 with my Duka years ago with no problems though I used a Nova PrintPod which also minimized exposure to the safelight.

You won't actually see it come up like B&W though. Until it goes through the bleach (blix) there's a dark layer - the unprocessed paper is brown, or was back then. Even after processing it looks milky until it dries.

 

[Gerald C Koch]

Since color paper is sensitive to all wavelengths of the visible spectrum it presents a special challenge to the use of a safelight. Usually a safelight filter is used which represents a compromise with the lowest sensitivity of the paper with the highest sensitivity of the human eye. Even so the light output must be kept low as not to fog the paper. Since the spectral sensitivity of a paper can be different for each manufacturer it is important to use the filter recommended by the paper manufacturer.

 

[Cybertrash]

If one were to use a processing drum, could you use a slightly brighter safelight during the "dry" part of the printing, as the print wouldn't be exposed to the light for the same amount of time, or would it be unwise to risk it?

 

[AgX]

Since color paper is sensitive to all wavelengths of the visible spectrum it presents a special challenge to the use of a safelight. Usually a safelight filter is used which represents a compromise with the lowest sensitivity of the paper with the highest sensitivity of the human eye. Even so the light output must be kept low as not to fog the paper. Since the spectral sensitivity of a paper can be different for each manufacturer it is important to use the filter recommended by the paper manufacturer.

RA-4 papers typically have a spectral sensitivity "gap" in a region of emittance of sodium-vapour lamps.

http://www.agfa.com/sp/global/en/binaries/RAP_C1C2_06_tcm611-42571.pdf

http://www.fujifilm.eu/uploads/tx_ffproducts/files/files/Fujicolor_Crystal_Archive_Paper_01.pdf



But as with any safelight: do a test under your specific conditions.

The Duka 10 has an aperture to reduce emittance. Furthermore, as with any other light, one could only use the light reflected from walls. Be aware that there is a Duka version too not employing a sodium lamp.

 

[BMbikerider]

It would not be a good idea to use dish printing with a safelight. In a drum or deep tank processor - yes. You may find you have problems keeping the developer in a very tight temperature range +/-.5 of a degree is what is needed for consistency. That is without the risk of fogging from a sodium safelight.

When exposing the paper under the enlarger I stand with my back to the safelight and the paper is in my shadow therefore cutting down the light reaching the sensitive surface. Even so there are times when I can detect slight fogging in the highlights that altering filtration won't remove.

 

[Gerald C Koch]

RA-4 papers typically have a spectral sensitivity "gap" in a region of emittance of sodium-vapour lamps.

The primates with their color vision evolved under a canopy of green leaves and a yellow sun. Therefore the human eye's greatest sensitivity is to yellow-green light. The sodium emission consists of a doublet in the yellow-orange region of the spectrum at 589.0 and 589.6 nm. Not optimal for either the paper or the human eye but close enough to be useful.

 

[Roger Cole]

It would not be a good idea to use dish printing with a safelight. In a drum or deep tank processor - yes. You may find you have problems keeping the developer in a very tight temperature range +/-.5 of a degree is what is needed for consistency. That is without the risk of fogging from a sodium safelight.

When exposing the paper under the enlarger I stand with my back to the safelight and the paper is in my shadow therefore cutting down the light reaching the sensitive surface. Even so there are times when I can detect slight fogging in the highlights that altering filtration won't remove.

I did, BTW, also use my Duke 50 with trays without problems, keeping the print face down. Processing times, even at room temperature, are short. I quit because the fumes from the open trays were choking me out of the darkroom and went to the Print Pod for that reason, which helped a lot. I never had fogging in the trays either but I didn't use them nearly as long - a few weeks, changed to the Pod and printed like that a couple of times a week for maybe two years.

I was using the old Tetanal RA4AT Ambient Temperature kit which had problems with bad blix and yellow highlights but I confirmed that wasn't due to the safelight (by comparing prints made in total darkness) but the chemicals. You don't have to tightly control temperature. Many people use Kodak RA4 at room temperature with adjustment to the time accordingly.

 

[Photo Engineer]

I suspect that no matter the safelight, you will never be able to use it at a high enough brightness for DBI. By that time it will be fogging the paper.

PE

 

[skystrick]

So the concensus seems to be: use a sodium-vapor light such as the Thomas or the Duka, but shutter it to a low level, and bounce it off the ceiling. Sounds do-able. Anything's better than pitch black.

Just curious - I've never used sodium-vapor darkroom lighting before - can I use it in place of my OC safelight for B&W printing, and in place of my Kodak #3 very-dark-green safelight for B&W film inspection during developing? Because if I can use a sodium-vapor safe light with everything - prints and film, color and B&W - I'd rather have it than my all my other safelights, simply because it's brighter.

 

[AgX]

It would not be a good idea to use dish printing with a safelight. In a drum or deep tank processor - yes. You may find you have problems keeping the developer in a very tight temperature range +/-.5 of a degree is what is needed for consistency. That is without the risk of fogging from a sodium safelight.

Jobo once made a combo of a small drum processor (for C-41 films) and a slotted tank (for RA-4 papers). Both controlled heated.

 

[Roger Cole]

So the concensus seems to be: use a sodium-vapor light such as the Thomas or the Duka, but shutter it to a low level, and bounce it off the ceiling. Sounds do-able. Anything's better than pitch black.

Just curious - I've never used sodium-vapor darkroom lighting before - can I use it in place of my OC safelight for B&W printing, and in place of my Kodak #3 very-dark-green safelight for B&W film inspection during developing? Because if I can use a sodium-vapor safe light with everything - prints and film, color and B&W - I'd rather have it than my all my other safelights, simply because it's brighter.

Yes and no respectively. It Dan be pretty bright for B&W too but no good for B&W film.

 

[skystrick]

Yes and no respectively. It Dan be pretty bright for B&W too but no good for B&W film.

Huh, strange that it'd be okay for B&W paper, but not B&W film.

I'm assumming that the sodium-vapor safelight is also totally out for the C41 film developing too?

 

[Roger Cole]

Huh, strange that it'd be okay for B&W paper, but not B&W film.

I'm assumming that the sodium-vapor safelight is also totally out for the C41 film developing too?

Why? B&W paper safelights are orange or red, because the papers are not sensitive to those colors. Safelights for DBI of B&W films are green, though the films are sensitive to green the human eye is most sensitive, so a color is chosen that will enable you to see the most at a level the film won't register.

And yes, it's out for C41 film. The only films that can really be developed with safelights, not counting the quick peek for DBI of pan films using a dark green, are orthochromatic films. The sodium vapor might work for that, but you'd be better off for much less money with a cheap red LED bulb.

Bear in mind too that the Duka is no longer made and the tube for it I think is no longer made either and, if it is, is very expensive (though they last a very long time.) I still have mine but don't use it, saving it for when I get back into color. For black and white I use a combination of a regular safelight and an LED unit by the enlarger.

Another point with the sodium vapor is that they don't come on suddenly and have to warm up, and I've heard switching transients from timers will damage them or at least severely limit the tube life anyway. Turn them on once at the start of your session and off when finished. This can make composing, focusing and dodging/burning hard to see on the baseboard if the light isn't kept away from the baseboard.

 

[skystrick]

Why? B&W paper safelights are orange or red, because the papers are not sensitive to those colors. Safelights for DBI of B&W films are green, though the films are sensitive to green the human eye is most sensitive, so a color is chosen that will enable you to see the most at a level the film won't register.

And yes, it's out for C41 film. The only films that can really be developed with safelights, not counting the quick peek for DBI of pan films using a dark green, are orthochromatic films. The sodium vapor might work for that, but you'd be better off for much less money with a cheap red LED bulb.

Bear in mind too that the Duka is no longer made and the tube for it I think is no longer made either and, if it is, is very expensive (though they last a very long time.) I still have mine but don't use it, saving it for when I get back into color. For black and white I use a combination of a regular safelight and an LED unit by the enlarger.

Another point with the sodium vapor is that they don't come on suddenly and have to warm up, and I've heard switching transients from timers will damage them or at least severely limit the tube life anyway. Turn them on once at the start of your session and off when finished. This can make composing, focusing and dodging/burning hard to see on the baseboard if the light isn't kept away from the baseboard.

Sounds good. I guess I'll go with the Thomas for printing, and keep my Kodal #3 for B&W DBI, and keep doing C41 in the dark.

I'll just build some sort of damper for the Thomas so I can kill the light for D&B without having to shut it off. I understand that it's like those mercury vapor lights in gymnasiums, takes time to warm up and get to color, can't do a quick off-and-on like a regular bulb.

Thanks for all the input, folks!

 

[Photo Engineer]

Panchromatic B&W film is sensitive to green light. It is just marginally less sensitive though and the human eye is marginally more sensitive. So, we cope and can do DBI very carefully. Color film is very green sensitive and thus you must be careful not to use green safelights at all.

Although, some color films and papers are built with a "window" in sensitivity so that the WR13 filter can be used with low wattage lights.

PE

 

[clayne]

Myself, no way in hell I'd use any safelight with film. The farthest I'd go is infrared goggles and last I checked they weren't cheap.

 

[Roger Cole]

They aren't THAT cheap but night vision is now in the "affordable, if you want it that badly" category. I've been thinking about getting some goggles for the darkroom.

I personally think developing pan film by inspection is not worth the trouble, but some people do like it and it works for them.

 

[Photo Engineer]

I have heard of the "green" light leaking from the eye cups of IR goggles fogging film.

PE

 

[Roger Cole]

So have I but people do it successfully. Ken Lee has written about it on his page. I'll look for the link.

 

[Ed Bray]

I have just adapted my darkroom to infra-red, the glasses are good with 940nm lighting which are cheap as chips from China, I bounce 4x 940nm lights (one in each corner of the 7ft 6in x 6ft darkroom) off the white ceiling and it is like daylight with the glasses on. Even my infra-red films are not sensitive to 950nm I have checked and there is no fogging even when left for 30 minutes.

The glasses I have though are not cheap, these are not night vision glasses but true IR glasses for use in darkrooms, they cost me 300 euros as second user items, new they are considerably more expensive. They have 2x active tubes, one for each eye strangely enough. EMO Elektronik

 

[Photo Engineer]

Roger, I have used IR as well and the trick is to keep the eyecups tightly over the eyes and to not let any of the green escape.

PE

 

[AgX]

[My infrared glasses] have 2x active tubes, one for each eye strangely enough. EMO Elektronik

Not strange. They enable you to see stereoscopic.

 

[Ed Bray]

I know, I was being flippant as most 'night vision goggles' only have the one tube.