Making Your Safelight Safer

albada · Aug 22, 2022

Ian Grant said:
Something that's missed is that bright Red safelights can affect the contrast range of variable contrast papers, too bright they don't fog paper, they do just the opposite "Latent Image bleaching" better known as the Herschel effect. This tends to limit the contrast range, it's going to be most noticeable in small darkrooms.

Ian: Thanks for mentioning this. I had never heard of the Herschel effect, so I researched that topic (translation: I googled it). I aimed my safelight at the ceiling to bounce all over the darkroom. It looks dark at first, but after becoming accustomed to it, I can easily see where things are. Hopefully that's well below the level where the Herschel effect begins.

Koraks: I read your 'tinker' blog in which you describe the sophisticated lighting of your multi-purpose darkroom. You make your own PCBs and solder your own SMT -- wow! A question (and maybe I missed this in your description): Does your timer turn off the red safelight? Doing so would make dodging/burning easier.

Mark Overton

koraks · Aug 22, 2022

albada said:
You make your own PCBs and solder your own SMT -- wow!

...and it's a lot less intimidating that it might seem! Making PCB's is kind of fun, BTW. It really resembles alternative printmaking in many ways. It's a sort of extremely high contrast cyanotype sort of thing.

albada said:
Does your timer turn off the red safelight?

No, it doesn't, although it's technically feasible to modify the system so that it does. There's a few ways I could pull this off, and when making both the enlarger controller and the safelight system, I kept these scenarios in mind so that they're fairly straightforward to add. I didn't actually do it (at least, not yet) mostly because it's just not really necessary. I find the baseboard image so easy to see that there's fairly little benefit in turning off the safelight. If needed, I can just reach into my pocket and use the remote to turn it off.

john_s · Aug 22, 2022

Ian Grant said:
Something that's missed is that bright Red safelights can affect the contrast range of variable contrast papers, too bright they don't fog paper, they do just the opposite "Latent Image bleaching" better known as the Herschel effect. This tends to limit the contrast range, it's going to be most noticeable in small darkrooms.

Ian

Thank you for that Ian. Time for a different safelight test! My very red (660nm) LEDs are very bright and my darkroom is very small.

Patrick Robert James · Aug 23, 2022

I use those small red LEDs that someone found at Superbrightleds years ago. I also put rubylith over them because you can't be too careful and I had a bunch of rubylith. My first darkroom nearly 30 years ago I had a Fireball I think it was called. A large bulb that was painted red. I don't know if they make those anymore but I doubt it. Just for kicks and giggles I plugged in one of those Kodak bullet safelights with the OC filter on it. Man that was dim, but back in the day that was normal, and I'm sure we all remember that. On the other hand, the LEDs are almost too bright I think. My darkroom is small.

I did do a half a$$ed test once to see if the red affected the shadows and didn't see anything. I might try it again and measure the blacks this time.

albada · Aug 23, 2022

Patrick Robert James said:
I did do a half a$$ed test once to see if the red affected the shadows and didn't see anything. I might try it again and measure the blacks this time.

It's better to check light tones because slight fogging will be obvious in light tones but not in dark tones.
Here's a link to the Kodak Safelight Test as posted by Matt King. It checks light tones. It's described in detail, but I'll summarize it here:

Cover half a test-strip the long way, and expose it with your enlarger enough to yield a uniform light gray.

Using your safelight instead of the enlarger, expose multiple steps in that strip as you would a normal strip. Kodak suggests going up to 7 minutes.

Cover the other half of the strip the long way, and expose it enough to yield a uniform light gray.

BTW, Kodak suggests cutting off the upper-left corner of the strip so you'll know which half is which.
You now have a test-strip of your safelight that was both pre-exposed and post-exposed with enlarger light. Develop. Any darker steps are fogging.

Ian Grant · Aug 23, 2022

john_s said:
Thank you for that Ian. Time for a different safelight test! My very red (660nm) LEDs are very bright and my darkroom is very small.

albada said:
Ian: Thanks for mentioning this. I had never heard of the Herschel effect, so I researched that topic (translation: I googled it). I aimed my safelight at the ceiling to bounce all over the darkroom. It looks dark at first, but after becoming accustomed to it, I can easily see where things are. Hopefully that's well below the level where the Herschel effect begins.

I was using a Photax/Paterson orange/red safelight in a very small darkroom around 1986/7, it was at the minimum recommended safe distance. I was surprised that I couldn't achieve the higher contrast grades with Ilford Multigrade FB.

There was a magazine article which highlighted the problem and explaining it was the exposure to red light causing the Herschel effect, Photax introduced a VC dome filter for their safelight around the same time, designed specifically for Variable Contrast papers. Essentially it's similar to the Kodak OC & Ilford 902 filters. Photax later merged with Paterson.

Those of us who have been on Ilford factory tours have seen the multiple 902 safelights in their paper confectioning area, very low intensity, probably wired in series.

Personally I find the colour output of OC/902 filters more pleasant to work with, if I was going to use Red LEDs I'd add a green filter to try and emulate the colour output of the OC/902\.

Ian

koraks · Aug 23, 2022

Ian Grant said:
if I was going to use Red LEDs I'd add a green filter to try and emulate the colour output of the OC/902\.

Don't do that. It just doesn't make sense. You'd be discarding virtually all the light output of the LED in the filter, keeping only a fraction of its secondary emissions. It would make more sense to take a tiny white LED and put that behind an OC902 just like you'd use a small tungsten bulb. I'm talking 0.5W white LED or something in that range.

Helge · Aug 23, 2022

Ian Grant said:
Something that's missed is that bright Red safelights can affect the contrast range of variable contrast papers, too bright they don't fog paper, they do just the opposite "Latent Image bleaching" better known as the Herschel effect. This tends to limit the contrast range, it's going to be most noticeable in small darkrooms.

Ian

Probably the same reason why you better preflash and latensify film with a green or failing that a full spectrum light. Even if we are talking infrared film.
The Herschel effect used to be a somewhat big concern for astronomical plates. It's still something we should heed under certain circumstances.

Ian Grant · Aug 23, 2022

koraks said:
Don't do that. It just doesn't make sense. You'd be discarding virtually all the light output of the LED in the filter, keeping only a fraction of its secondary emissions. It would make more sense to take a tiny white LED and put that behind an OC902 just like you'd use a small tungsten bulb. I'm talking 0.5W white LED or something in that range.

Well, that's what I plan to do when I run out of 15w Pigmy bulbs, but they do last a long time and I have quite a few.

My current darkroom is 12"x13" and I use 3 safelights for B&W printing 2 Paterson.Photax VC and a Kodak beehive with an OC, there's also a safelight with a 906 Dark Ruby Red for Harman Direct Positive paper, and a couple of Kodak Beehive safelights with Wratten 10/19H for colour printing, these are used indirectly.

In previous darkrooms I've used dimmer switches to control the level of darkroom illumination, it's an easy solution in a small darkroom.

Ian

koraks · Aug 23, 2022

Ian Grant said:
In previous darkrooms I've used dimmer switches

Yes, that works; in case you consider something similar in the future, keep in mind many led bulbs are not dimmable.

I haven't done anything with x-ray film for a while, but if I ever do, I'll probably have to devise something specifically for it. It's rather finicky stuff and regular b&w safelights,even the deep red ones, generally fog unless dimmed to a very low level.

Ian Grant · Aug 23, 2022

koraks said:
Yes, that works; in case you consider something similar in the future, keep in mind many led bulbs are not dimmable.

I haven't done anything with x-ray film for a while, but if I ever do, I'll probably have to devise something specifically for it. It's rather finicky stuff and regular b&w safelights,even the deep red ones, generally fog unless dimmed to a very low level.

The Ilford 905 Olive Green is designated for X-ray materials., or the 914/Kodak NX or GBX-2 for blue and green sensitive X-ray films.

I think the Wratten 10/10H or Ilford 908 colour paper safelight filters would be the easiest to find and would be safe with X-ray films, essentially they are a very dark amber/brown, they could be used direct, unlike with colour papers.

Here's a list of Safelight filters, there's a link on the page to the Ilford list.

Ian

koraks · Aug 23, 2022

Ian, thanks. I'll stick with LED though. For x-ray, the most straightforward solution in my situation is to just add a new program to my lighting software that runs the red LEDs at low intensity. No additional hardware needed. I know this works, because I did x-ray stuff (development by inspection etc.) under a similar setup in my previous darkroom.

There are several problems with e.g. a #905 for x-ray. One of them being that the x-ray film I worked with and 'preferred' (insofar as I liked it, which I didn't, really) is orthochromatic. This means that an olive green filter will only allow very, very limited light intensity, otherwise the film fogs. For blue x-ray, it might be OK. With deep red, you stay much further away from the sensitive spectrum of the film and hence you can throw a lot more light at it unpunished. Another issue is availability and durability; some or most of these filters aren't available anymore new, so trying to find them in the second hand market place is the only viable option, and old filters are a gamble in terms of quality.

To be frank, I understand how some people are used to these older filters because it's what was available in the day, so it feels natural and comfortable for them to resort to them, but from my perspective, it's just not the optimal solution given today's available technology.

john_s · Aug 23, 2022

koraks said:
Yes, that works; in case you consider something similar in the future, keep in mind many led bulbs are not dimmable.

I haven't done anything with x-ray film for a while, but if I ever do, I'll probably have to devise something specifically for it. It's rather finicky stuff and regular b&w safelights,even the deep red ones, generally fog unless dimmed to a very low level.

Bulbs for mains voltage of course contain an AC to low voltage DC converter as the LEDs themselves need only a couple of volts each, or maybe some need a bit more. The electronics for that are the problem with dimmers.

My safelights are large arrays of discreet LEDs fed by about 20V DC and my dimmer is just a rheostat (2 pins of a potentiometer). I understand that that is very inelegant but it does work and nothing gets hot. I have read that when you lower the current (dim) a single colour LED the spectrum narrows which is probably better as far as paper safety is concerned.

I will devise a different safelight test because of the possible Herschel effect. Should I try it with my VC enlarger head set on a high contrast? Excessive safelight exposure before or after the test exposure of a calibration negative, or doesn't it make a difference?

koraks · Aug 23, 2022

john_s said:
LEDs themselves need only a couple of volts each

Sort of. They're constant current devices, and the forward voltage ranges from about 1.8V to near 5V depending on emitter wavelength.
In LED 'bulbs' there are usually several LEDs in series together with a current limiting device. The topology of the latter varies and I see new approaches on the market from time to time. Depending on how that's implemented, the bulb can or cannot be dimmed using a classic thyristor dimmer.

john_s said:
I understand that that is very inelegant

Haha, yes, that's probably the most unfortunate solution imaginable But hey, if it works for you...

john_s said:
Should I try it with my VC enlarger head set on a high contrast? Excessive safelight exposure before or after the test exposure of a calibration negative, or doesn't it make a difference?

I'd try either if you want to be thorough.

Raghu Kuvempunagar · Aug 23, 2022

How reliable is the CD test? Clearly, if the test reveals green or blue, then the safelight is not safe for VC paper and B/G sensitive X-ray film. But if the test reveals no green/blue, is it assured that the safelight is safe for VC paper and B/G sensitive X-ray film?

I did the CD test on a smart LED bulb and found that when the colour is set to a specific red point in the colour wheel, CD test shows only red (and no blue/green) in both minimum and maximum brightness modes. Does this mean that LED light is safe (at least in the minimum brightness mode and dimmed further using a diffuser)? Is it possible that there could still be some blue and green light faint enough that the CD test and/or the eyes are not able to catch?

I also tested Kaiser 4018 safelight with Kaiser 4015 multigrade filter. It revealed a hint of green but this filter is rated safe for VC paper. Does this mean that at the intensity of the light produced, it is safe for VC paper but probably not for X-Ray film?

Has anyone used LightSpectrumPro EVO or similar app to analyse the spectrum of the light produced by the safelight? How reliable is it?

Patrick Robert James · Aug 23, 2022

albada said:
It's better to check light tones because slight fogging will be obvious in light tones but not in dark tones.
Here's a link to the Kodak Safelight Test as posted by Matt King. It checks light tones. It's described in detail, but I'll summarize it here:

Cover half a test-strip the long way, and expose it with your enlarger enough to yield a uniform light gray.
Using your safelight instead of the enlarger, expose multiple steps in that strip as you would a normal strip. Kodak suggests going up to 7 minutes.
Cover the other half of the strip the long way, and expose it enough to yield a uniform light gray.

BTW, Kodak suggests cutting off the upper-left corner of the strip so you'll know which half is which.
You now have a test-strip of your safelight that was both pre-exposed and post-exposed with enlarger light. Develop. Any darker steps are fogging.

I didn't just step off a turnip truck Mark.... I was referencing Ian's post regarding the Hershel effect, in which bright red light can bleach areas of high density, i.e. the shadows. But thanks for the Photo 101 info....

albada · Aug 23, 2022

Raghu Kuvempunagar said:
How reliable is the CD test? Clearly, if the test reveals green or blue, then the safelight is not safe for VC paper and B/G sensitive X-ray film. But if the test reveals no green/blue, is it assured that the safelight is safe for VC paper and B/G sensitive X-ray film?

Perhaps not for FOMA VC paper. Back in posting #15 here, Doremus Scudder stated that "Foma papers, for example, don't play well with OC safelights; they need red." That tells us that FOMA's sensitivity extends into longer wavelengths than Ilford's. If the tail of its spectral sensitivity curve reaches 620 nm or longer, then a typical red LED would eventually fog it. So even if a safelight passes the CD test, it would be prudent to perform Kodak's safelight test on your material.

albada · Aug 23, 2022

Patrick Robert James said:
I didn't just step off a turnip truck Mark.... I was referencing Ian's post regarding the Hershel effect, in which bright red light can bleach areas of high density, i.e. the shadows. But thanks for the Photo 101 info....

I misinterpreted your posting; sorry about that.

For those outside the USA: "just stepped off the turnip truck" is a colloquial American expression that means "ignorant".
In fact, *I* just stepped off the turnip truck as I acquired an enlarger only two years ago, so printing is still new for me.

MattKing · Aug 23, 2022

albada said:
For those outside the USA: "just stepped off the turnip truck" is a colloquial American expression that means "ignorant".

Or more charitably, "naïve and not well informed".

albada · Aug 26, 2022

Those who wish to test their safelights can do so using the Ilford method described here:
Testing Your Safelights
It's about the same as the Kodak method, but more clearly written.

Doremus Scudder · Sep 6, 2022

Testing for degradation from the Herschel Effect is easy; just make a print at your highest contrast settings while taking lots of time and with your red safelights at full power, then make the same print in total darkness. Compare and see if there is reduced contrast in print #1.

Doremus

CMoore · Sep 8, 2022

Hilo said:
I have the old yellow-green bulbs in my darkroom which is a space of 35 square meters. 12 bulbs in two groups of 6. The bulbs are where the walls meet the ceiling, in "open" wall sockets and always more than 2 meters away from the easels and the chemicals. The walls and the ceiling are painted off-white.

When I expose all these lamps turn off automatically. I do a lot of 50x60cm fiber prints with exposures of 70 seconds and often again that with burning.

This has been my way since the late nineties, in the two darkrooms I had and have. I tested in both darkrooms if any fogging occured, it never did. Apart from total darkness when exposing, I am also used to leaving only one of these lamps on during when the paper comes out of the box and placing it in the easel.

I have only used Agfa Record Rapid and Ilford Warmtone papers.

My only worry is that these yellow-green bulbs dissappear. I think they only make the brighter yellow ones now. For over twenty years I buy the yellow-green ones whenever I see them. I can probably print for another 100 years.

50x60.......wow.!!!

That is about 22x24 inches.?

At any rate, some pretty big photos.
Would love to see a video of your process if you have one available.
good luck

Hilo · Sep 8, 2022

CMoore said:
50x60.......wow.!!!

That is about 22x24 inches.?

At any rate, some pretty big photos.
Would love to see a video of your process if you have one available.
good luck

No video, so I will describe

That is 20x24 inches. I have a large darkroom sink that can have 3 trays for 20x24 paper, plus there is a second smaller sink with 1 tray for 20x24 inches. The latter is to stack the prints in water, after fixing. Going down one size, the large tray was designed to hold 4 trays for 16x20 inches to be able to have 2 fixing trays.

I have a 20x24 in. 2 bladed RRB easel and otherwise printing this size is pretty much the same as with smaller sizes. Sometimes to focus is difficult, with the Focomat Ic in particular I just manage to stretch myself to be able to turn the lens while looking into the grainfocuser. The Focomat IIc is easier in that. It is one of the reasons why I added two non-automatic focus enlargers, a Valoy II modified to do this size and a Durst L-1000 that is wall-mounted. These both take lenses slightly more wide-angle, bringing down the enlarger by quite a bit.

To dry, I hang the prints using 2 lines above the sink and I have a 20x24 in. dry-mounting press to flatten the prints.

CMoore · Sep 9, 2022

Hilo said:
No video, so I will describe

That is 20x24 inches. I have a large darkroom sink that can have 3 trays for 20x24 paper, plus there is a second smaller sink with 1 tray for 20x24 inches. The latter is to stack the prints in water, after fixing. Going down one size, the large tray was designed to hold 4 trays for 16x20 inches to be able to have 2 fixing trays.

I have a 20x24 in. 2 bladed RRB easel and otherwise printing this size is pretty much the same as with smaller sizes. Sometimes to focus is difficult, with the Focomat Ic in particular I just manage to stretch myself to be able to turn the lens while looking into the grainfocuser. The Focomat IIc is easier in that. It is one of the reasons why I added two non-automatic focus enlargers, a Valoy II modified to do this size and a Durst L-1000 that is wall-mounted. These both take lenses slightly more wide-angle, bringing down the enlarger by quite a bit.

To dry, I hang the prints using 2 lines above the sink and I have a 20x24 in. dry-mounting press to flatten the prints.

Melvin J Bramley · Feb 11, 2023

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