PDA

View Full Version : Film sensitivity to GraLab clock glow



wskmosaic
12-Aug-2010, 16:37
How well does black and white film do (I'm using FP-4) when exposed to the faint green glow of a darkroom timer? My old GraLab's got a raucous buzzer, but not being able to see it is frustrating.
Warren Kornberg

Kevin Crisp
12-Aug-2010, 16:45
If it is faint, as in the lights have been off for several minutes in the darkroom, it isn't generally a problem. If you put it on a shelf so that it cannot shine down directly into the sink or wherever you are handling film, it helps a lot. Fred Picker said it was exactly the right color to fog film, but who knows how he knew that?

What I did was tape a big square flap of black flannel on top of mine. It can be flopped down over the front or folded and put up on the top exposing the dial. If I am using it, I lift the flap up after the lights are out. The dial will be very faint, but readable. Yes, they are wake-the-dead loud.

Ken Lee
12-Aug-2010, 17:15
It has never bothered my film. I keep it a few feet away. It has never bothered any paper either.

These timers have been around for a long time :)

Gem Singer
12-Aug-2010, 17:41
To charge a GraLab's luminous dial to it's max., expose it to a florescent light for a few minutes. It will glow brighter for a longer period of time.

Holding unexposed film directly against the brightly charged luminous dial for a few seconds will expose film and paper, but only at the point of contact.

Otherwise, as long as you do not hold the light sensitive material directly against the luminous dial, it does not fog film or paper.

If you're in doubt, test it for yourself. I did.

(Ken, that statement is anecdotal. I have no scientific data to back up it up).

jp
12-Aug-2010, 18:03
I throw a towel over mine while loading/unloading film.

When processing film in a tray, it is on the other side of my darkroom (about 5-6' away) and I stand between the gralab and the trays. Never had a problem that way. Having it on a shelf above your sink is probably fine too, as but if you wear white it could illuminate you and fog the film.

You could probably muffle or disconnect the buzzer if you wanted.

bigdog
12-Aug-2010, 18:29
You could probably muffle or disconnect the buzzer if you wanted.

Later models had a volume control.

Gralab now makes other models besides the 300 (167, 170, etc) that do not have the luminous dial, and may have one outlet rather than two (depending on model). I use one of those for film processing. They turn up on the auction site often enough if you look closely.

http://www.gralab.com/products/details.asp?ID=3

Brian Ellis
12-Aug-2010, 18:43
I had a GraLab timer on a shelf about three feet above and to the right of my developer tray. It never created a problem. Remember the inverse square law of light fall-off, under which the drop-off is inversely related to the square of the distance from the source (or something like that). So if you're three feet from the source you're receiving 1/9th the amount of light as you'd receive at the source (or something like that) and if you're four feet away you're receiving 1/16 (or something like that). Considering how weak that glow is from a Gralab timer to begin with, and considering that your film is surely at least a few feet away, it's highly unlikely that you'd have a problem.

rdenney
12-Aug-2010, 19:33
Mine was always on a shelf right above the sink, and I developed sheet film in hangers over open tanks. I never had a problem at all with FP4, or even with faster film.

Rick "who wouldn't worry about it" Denney

Vlad Soare
13-Aug-2010, 00:20
I use a radio alarm clock with luminous, dark green digits, like the one in the attached picture.
I couldn't see any trace of fog whatsoever with HP5+ or TMY-2, which are more sensitive than FP4+.
If this clock doesn't fog films, then neither will the Gralab. Don't worry about it.

Ken Lee
13-Aug-2010, 02:41
(Ken, that statement is anecdotal. I have no scientific data to back up it up).

Wizenheimer ! :rolleyes:

Wade D
13-Aug-2010, 03:22
I use a Gralab 520 digital timer for dip and dunk in open tanks. It can be set to dim so the red digits are very faint. I've never had a problem with fogging film. It is about 6 feet away from the tanks. Luminous dials are also safe. The small amount of light from either will not affect your film.

Steve Goldstein
13-Aug-2010, 03:47
My Gralab sits about a foot above and to the side of my developing trays on a small shelf, facing towards the ceiling. It seems pretty bright when I first turn off the fluorescents but I've never had a problem with TMY-2. I'm careful not to wear highly reflective clothing (white shirt, aluminum-foil vest, etc.) when developing film. I keep my glasses on so I can see the timer, but as long as I hold my head up vaguely straight they don't seem to reflect into the tray.

jonathan_lipkin
13-Aug-2010, 06:39
I'd agree with everyone above. I had a gralab timer directly above my sink where I would tray develop 4x5 sheet film and never had any problems.

aduncanson
13-Aug-2010, 07:37
The only white lights in my darkroom are fluorescents which, as Gem noted above, do an excellent job of charging luminescent dials. As an extra precaution, I simply avoid turning on the white lights before handling film. I have never had a problem with HP5+ or Tri-X.

Gem Singer
13-Aug-2010, 08:04
Aduncanson, like you, I learned from experience, a florescent fixture glows for a few minutes after it is turned off.

I made sure that the darkroom door was light tight, covered the glowing timer, turned off the florescent light fixture in the ceiling, and after about a minute, I could see the outline of my hand in the dark.

Looked up and noticed that the two forty inch florescent tubes in the ceiling fixture were still glowing dimly. Probably would have fogged fast film had I exposed it to that glow.

I now wait about five minutes until the afterglow disappears before loading film in the darkroom.

Drew Wiley
13-Aug-2010, 09:35
Some film/dev scenarios have quite a bit of sensitivity in the toe of the film. I learned
the hard way. Any timer is now on a shelf BELOW the sink.

GPS
13-Aug-2010, 09:46
Why tempt the film? In a certain way, the film sees better the light than our eyes (the retina has greater light sensitivity but unlike our eyes, the film is capable of accumulating the light effects). Is it so difficult to put the light source in a kind of a lens shade and keep the light visible just from the angle which the film cannot reach?

Jerry Bodine
13-Aug-2010, 10:29
a florescent fixture glows for a few minutes after it is turned off.

I made sure that the darkroom door was light tight, covered the glowing timer, turned off the florescent light fixture in the ceiling, and after about a minute, I could see the outline of my hand in the dark.


I, too, did this check when I had completed the darkroom construction. And noticed one the fluoroscents glowing enough to see my hand. It turned out to be a leaky ballast. After replacing the ballast I never again used those lights during a developing/printing session, but instead use the 100W bulb-in-reflector hanging above the sink when I need room light. BTW, I also have small luminous tapes placed at numerous locations around the room to help me find things in the dark and to prevent running into things (kinda neat ... like a starry, starry night). Probably overkill, but I've never had any fogging.

Vlad Soare
13-Aug-2010, 10:49
What I don't really understand is why you would use fluorescent tubes in the darkroom. They take minutes to reach their full power, glow for minutes after being turned off, and give an ugly light which makes assessing prints difficult. Why would you want them in your darkroom? :confused:
I know they have some benefits, and I use a lot of them in my house. Just not in the darkroom.

Henry Ambrose
13-Aug-2010, 10:53
What I don't really understand is why you would use fluorescent tubes in the darkroom. They take minutes to reach their full power, glow for minutes after being turned off, and give an ugly light which makes assessing prints difficult. Why would you want them in your darkroom? :confused:
I know they have some benefits, and I use a lot of them in my house. Just not in the darkroom.

Yep.
Incandescent lamps would be a lot better choice.

And GraLab timer glow won't hurt film.

Gem Singer
13-Aug-2010, 11:49
Vlad,

My makeshift darkroom is located in a large walk-in closet adjacent to the master bathroom in my house.

The florescent ceiling fixture was installed when the house was built. It was not my choice. However, no need to replace it. I just don't use it when dealing with light sensitive materials in that space.

aduncanson
13-Aug-2010, 12:17
What I don't really understand is why you would use fluorescent tubes in the darkroom. They take minutes to reach their full power, glow for minutes after being turned off, and give an ugly light which makes assessing prints difficult. Why would you want them in your darkroom? :confused:
I know they have some benefits, and I use a lot of them in my house. Just not in the darkroom.

Maybe it is because I do most of my enlarging with a cold light head.;)

I thought about this pretty thoroughly and decided that it was a compromise I could live with. New "Full Spectrum" fluorescents (http://www.amazon.com/Bell-Howell-Sunlight-Desk-Lamp/dp/B003UVK4W0/ref=sr_1_6?ie=UTF8&s=hi&qid=1281726653&sr=1-6)are not perfect, but actually give pretty nice light for evaluating B&W prints, (I like to assess and view prints quite well lit.) make very little heat, and do not exhibit appreciable delay in reaching full brightness. The glow certainly does not affect my enlarging or contact paper, and as I indicated I have a simple and perfectly effective way of avoiding any problem they may cause with film.

Jerry Bodine
13-Aug-2010, 16:06
What I don't really understand is why you would use fluorescent tubes in the darkroom. They take minutes to reach their full power, glow for minutes after being turned off, and give an ugly light which makes assessing prints difficult. Why would you want them in your darkroom? :confused:
I know they have some benefits, and I use a lot of them in my house. Just not in the darkroom.

Vlad,
I installed fluorescents mainly because they generate much less heat than incandescents. I don't use them for print assessment, and they are turned off during a printing session, but I use the room for other activities as well and the light output is not objectionable. Regarding the heat, I can control the temperatures of my chemicals when prepared in the trays for printing, but over the course of a long printing session the room temp can sometimes increase by over ten degrees, necessitating the use of the sink as a water jacket to maintain 20C in the solutions for consistency. So my intent is to minimize the generation of heat in the relatively small room size.

Harold_4074
17-Aug-2010, 17:56
Looked up and noticed that the two forty inch florescent tubes in the ceiling fixture were still glowing dimly. Probably would have fogged fast film had I exposed it to that glow.

Could you take a picture of that and post it for us? :)

I'm being facetious, but only partly---if you tried to deliberately make an image in the lowest light levels that you eyes can detect, the reciprocity correction would probably try the patience of a statue.

Like just about everyone else, I have been startled to discover that the timer that I have been using for years can provide enough glow for me to distinguish objects while I am developing film, and my darkroom "white light" is only two 40-watt bare incandescent bulbs, so supercharging the phosphor by fluorescent is not a factor. Film supposedly loses much of its sensitivity as it develops (which makes develop-by-inspection practical) so that helps as well.

I actually wonder if perhaps with advancing age the eye becomes more sensitive to light!

Gem Singer
17-Aug-2010, 18:52
Harold,

If I can see the outline of my hand in a darkened room, I believe that the light is bright enough to have an effect on light sensitive materials, especially 400 speed film.

If it's not bright enough to noticeably fog film or paper, it probably will have some sort of effect on it.

For example, I know from experience that an unsafe safe light will degrade the highlights in a print.

DanK
17-Aug-2010, 19:53
I've never had a problem with Gralab timers, and have more than one mounted on the wall above the trays (16 to 18 inches.)

The older Time-O-Light timers had more illumination on the face - I always covered these when handling film.

Safelights tend to be the biggest culprits - and seem to get worse over time - a good safelight last year, sometimes isn't as great this year...

Fluorescents do have the ability to fog both film and paper, IME. I had two 2 light eight foot fixtures in my first darkroom, and had an obvious glow immediately after turning them off, and for a good bit after. I used incandescent clamp lights prior to handling film, until I replaced the flourescents.

As with anything, as long as you are aware of the potential problem you can take precautions.

A couple items often overlooked are wristwatches with the glowing faces...and cell phones... in the past, I've seen students with fogged film from both - watch on while loading film, and cell phone in shirt pocket when they get a call and it lights up...

Thanks,
Dan

Harold_4074
18-Aug-2010, 13:07
If I can see the outline of my hand in a darkened room, I believe that the light is bright enough to have an effect on light sensitive materials, especially 400 speed film.

If it's not bright enough to noticeably fog film or paper, it probably will have some sort of effect on it.

For example, I know from experience that an unsafe safe light will degrade the highlights in a print.

I agree completely (I said I was being facetious :) ).

Pre-exposure of film or paper to lift the very toe of the curve into the neighborhood of the fog density is a technique certainly older than I am; doing this unintentionally is certainly not good craftsmanship, even if the effect is not immediately obvious. It is one of the things which complicates "testing" of safelights by developing "unexposed" paper.

Afterglow from tubular fluorescents in a small darkroom is problematic for a reason that I don't think has been mentioned. Illumination from a point source falls off as 1/(distance squared), but that from an infinitely long "line" source only falls off as 1/(distance), and this makes a big difference. Four-foot tubes are not exactly infinitely long, but if the distance is comparable to the length of the tubes the effect will still be there. For example, on a three foot high bench under an eight foot ceiling, with end-to-end four foot lights, the illumination will definitely not obey an inverse square law.

Our more "point like" sources (small clocks, even the ring of numbers on a Gralab) are more innocuous for this reason, even if they are fairly "bright". And that tiny pinhole in the aluminum foil taped over the window, even if it is hard to look at with dark-adapted eyes, will probably not do much unless it forms an image of the outdoors on your working surface!

Drew Wiley
18-Aug-2010, 13:28
I once equipped my dkrm with high-frequency ballasts which largely eliminated the
afterglow issue, but created havoc with any hi-tech enlgr controls nearby due to EMI.
So now I just wait for the afterglow to disappear in the work areas. Over the sink itself I strictly use incandescent bulbs, and even the safelight is the old-fashioned type.

Vlad Soare
18-Aug-2010, 23:03
I'm not sure the after-glow is entirely a ballast issue. I think it has more to do with the fluorescent inner coating of the tube, which continues to emit some light even after the UV emission has ceased. Or maybe it's the mercury vapours that continue to emit some UV even after the electrical current has been interrupted? I'm not sure which one is true (possibly both? :)), but I suspect that the cause of the after-glow is something of this sort, and not necessarily the ballast.
A defective or low quality ballast can probably make it worse, but I think that even with the best ballast in the world there will still be a bit of after-glow.

Cletus
20-Aug-2010, 04:06
Funny, I was curious about this and did a little test on it last night. I have a Luminox wristwatch that has pretty dang bright dial that doesn't need to be "charged" to emit it's glow - something like Tritium, but not - and I've always wondered if it would fog film.

So in total dark, I unreeled about 6" of 35mm 400ISO film and held the watch face directly against it for at least one full minute and probably two. Then, I marked that spot (snipped a little off the edge with scissors) and pulled the next 6" out of the roll. This time, I just held the watch face near the emulsion side, a few inches away and kind of moved around slowly in that orientation for about 5 minutes.

Last, another 6" and about 5 minutes, this time with the film out in the "open", but not necessarily 'aiming' the watch dial at the film. Most of the time, the watch dial on my wrist was away from the film - if you wear your watch on the inside of your wrist, YMMV on this one. This last was an attempt to somewhat simulate actual handling of the film where it might occasionally "see" the glow from the watch.

Following all that, the film was developed at 1600ISO in 1+50 Rodinal (not the best developer for this maybe) for 18 minutes.

Here's the results: First test, watch left a big, dense black spot where I had held it against the emulsion. Second test, no discernible fogging that I could see, (with caveat that I should have used film that was unexposed from the camera - I used an old roll of exposed film for this, thinking it would be good enough, but the image detail might be obscuring test results). Third test, no discernible fogging.

Conclusion: Safelight (or more powerful Luminox Watch) glow should be safe for normal ISO films as long as the exposure from the glow is kept relatively indirect to, or at least not right up against, the emulsion for short periods (<10 min.) of time while processing.

I have done a similar test with paper and can detect zero fog, even with the watch face directly against the paper (I'd never do this in practice) and I intend to rerun this test with some totally unexposed 400 film in the future with a better developer, maybe Xtol.

Cletus
20-Aug-2010, 04:14
Whoops! Correction on last comments:

"Conclusion: Safelight (or more powerful Luminox Watch) glow should be safe..."

I meant to say TIMER, not safelight. I would not recommend sticking exposed, unfixed film under your safelight! I don't think it'll hold up to that!

Gem Singer
20-Aug-2010, 07:20
Cletus,

You're conclusions regarding the safety of the glow from a luminous dial are the same as mine (see post #4 in this thread).

A few years ago, I purchased a new GraLab 300 timer (the one with the gray plastic case) and noticed that the dial and the hands glowed much more brightly than my old black metal-cased GraLab 300.

Tested it after charging with florescent light to make it glow as brightly as possible.

It fogged film at the contact point where I held it directly against the luminous dial. It fogged paper only after holding it there for a much longer time.

ZoneIII
21-Sep-2010, 11:43
I have used a Gralab for many years with no fogging. My Graylab is about three feet from the developer tray on a shelf above my sink. However, I am using a newer Gralab timer now (the type made of plastic) and the luminosity is so weak (the opposite of what another poster here reports) that with the room lights off I can hardly see the Gralab after a couple minutes. I attached little pieces of luminous tape on the dial and hands. That was REALLY bright - so bright that I was concerned. I could actually see my hands and the trays once my eyes acclimated to the dark. So, I cut the luminous tape with a razor blade that I had attached to the timer and removed most of the tape so that they were about 1/3rd the size I had orginally made them.

A couple of other related comments: The inverse square law of light law really applies to point light sources. The luminous dial of a Gralab timer isn't a point light source but, for practical purposes, the rule is still useful. However, the Inverse Square Law was described incorrectly in page one of this thread and that should perhaps be clarified. Light intensity is not 1/9th of what it is at the light source when measured at three feet from the light source or, in another example, 1/4 of the intensity at two feet from the light source as explained. If it was, what would it be at 3 meters from the light source? It wouldn't be 1/9th of the intensity obviously. You have to start with a distance from the light source, not the light source itself. So, for example, say light intensity was X at a given distance from the light source, it would be 1/4 of that intensity if you doubled he distance. If you tripled the distance, light intensity would be 1/9th of what it was at the initial distance. In other words, it applies to the difference in two distances from the light source, not the distance from the light source itself.

Lastly, remember that if you get slight fogging of the film, it can usually be burned through with no problem when printing. In other words, printing time may just be slightly longer. However, fogging can also reduce contrast just as it can when you pre-fog film or paper so you may have compensate for that - or you may already be doing it without realizing it. My base + fog densities have never shown any fogging over the years when processing in open trays with a Gralab about three feet from the developer tray. However, that could be simply because any fogging didn't reach the threshold of the film but it may have fogged the low density areas. If it is, it has never been a problem and my calibration is compensating for it. It would be interesting to test this just out of curiousity. Maybe I will do that the next time I test a film.

BTW, I developed some film last night with my REALLY bright tape added to my Gralab and it doesn't appear to have caused a problem but I didn't test it so I can't say for sure. But they look good and are certainly printable. I have already removed most of the tape, though, because it really was bright. The tape I used supposedly glows for 24 hours once charged. I don't know about that but it sure glows a lot better than my newer-style (plastic) Gralab which, as I said, I almost couldn't see after a few minutes of dark. http://i12.photobucket.com/albums/a228/zoneIII/Bahai-Temple-ForWebS.jpg

Sirius Glass
21-Sep-2010, 13:07
I'd agree with everyone above. I had a gralab timer directly above my sink where I would tray develop 4x5 sheet film and never had any problems.

My experience too.

Steve