How dark should a darkroom be?

AFlood · Jan 11, 2010

My darkroom has loads of light leaks. I got quite stressed about trying to get rid of them (which is especially hard since I cant install anything permanent in my parents bathroom).
I got so frustrated with it I stopped enjoying what I was doing. In the end I gave up and just started using it how it was.
It works fine.

Alex

keithwms · Jan 11, 2010

Paint it Black (for Ralph)

Ralph sees my red door and he wants it painted black
No colors anymore he wants them to turn black
I see the girls walk by dressed in their summer clothes
I have to turn my head until my pupils close

I see a line of cars and they're all painted black
With flowers and my love both never to come back
I see people turn their heads and quickly look away
Like a new born baby it just happens every day

I look inside myself and see my heart is black
I see my red door and must have it painted black
Maybe then I'll fade away and not have to face the facts
It's not easy facin' up when your whole world is black

No more will my highlights turn a deeper grey
I could not foresee this thing happening to you

If I look hard enough into the settin' sun
My love will laugh with me before the mornin' comes

I see my red door and Ralph wants it painted black
No colors anymore I want them to turn black
I see the girls go by dressed in their summer clothes
I have to turn my head until my pupils close

Hmm, hmm, hmm,...

Ralph wantsa see it tainted, tainted black
Black as night, black as coal
He wantsa see the sun blotted out from the sky
He wantsa see it tainted, tainted, tainted, tainted black
Yeah!

Hmm, hmm, hmm,...

~~~

sorry Ralph, had to....

RalphLambrecht · Jan 11, 2010

I feel flattered. Nobody has ever dedicated a song to me before.

I'll frame this!

Thanks you, so much.

keithwms · Jan 11, 2010

Put it in your book, I won't charge much commission

iman · Jan 11, 2010

keithwms said:
Wait, I just checked and it's much more spectacular than that:

http://www.tacomaeyecarecenter.com/Eye.html

The single-photon assertion is a bit controversial as it depends critically on the angle at which the light is seen (b/c of the distribution of rods on the retina) and on the condition of the eye and how many carrots the subject has in his/her diet Turns out that the brain filters out much of the noise containing the single-photon information. But, in the statistical sense, the scotopic vision is actually sensitive to a single photon.

Regarding light under the doors, of course the very safest policy is to strive for complete darkness, but I am reporting, with very high confidence, that a bit of light under the door in my darkroom has had no measurable effect. And I have worked with IR film extensively.

There are many things in photography that people sweat and fuss over but which ultimately turn out to be moot most of the time. This is not the right profession for worry-warts: their creativity can simply grind to a miserable halt. There are just too many potential technical pitfalls to obsess over: MLU, 1/FL, aperture for best MTF, center post or not, base fog... etc. etc. Best policy is to experiment, establish your own best practices, and go with what works for you.

Individual photoreceptors are sensitive to a single quantum. To see a light, however, you need 4-5 quanta. This is a very famous experiment in psychology - Hecht, Shlaer and Pirenne, I believe. Also, this is quanta at the receptors, not quanta at the eye. The optics filter out about 90%, so you need 40-50 quanta at the cornea. Even then, this is under highly idealized laboratory conditions. In the real world, the perception is not anywhere near as sensitive.

The tacomaeyecarecenter.com site has many errors in their "facts":

1. " * The eye adjusts to 10-billion fold changes in
brightness adjusting for daylight and the dimmest
moon light"

The eye adjusts to luminance, not brightness. Luminance is a measure of intensity. Brightness is a psychological sensation, so the statement makes no sense. Also, the luminance range is more like 10's to 100's of millions, not 10 billion.

2. * "Eye translates a depth perception beyond any
known camera"

This make no sense whatever. Cameras record images. Period. They don't see depth or anything else for the matter. The viewer has to put the third dimension back into the 2D image, regardless of whether that image is viewed directly or in a photograph.

3. * On a clear dark night the eye can see a lit candle
from 30 miles away

I don't believe this.

keithwms · Jan 11, 2010

iman said:
Individual photoreceptors are sensitive to a single quantum. To see a light, however, you need 4-5 quanta. This is a very famous experiment in psychology - Hecht, Shlaer and Pirenne, I believe. Also, this is quanta at the receptors, not quanta at the eye. The optics filter out about 90%, so you need 40-50 quanta at the cornea. Even then, this is under highly idealized laboratory conditions. In the real world, the perception is not anywhere near as sensitive.

The tacomaeyecarecenter.com site has many errors in their "facts":

1. " * The eye adjusts to 10-billion fold changes in
brightness adjusting for daylight and the dimmest
moon light"

The eye adjusts to luminance, not brightness. Luminance is a measure of intensity. Brightness is a psychological sensation, so the statement makes no sense. Also, the luminance range is more like 10's to 100's of millions, not 10 billion.

2. * "Eye translates a depth perception beyond any
known camera"

This make no sense whatever. Cameras record images. Period. They don't see depth or anything else for the matter. The viewer has to put the third dimension back into the 2D image, regardless of whether that image is viewed directly or in a photograph.

3. * On a clear dark night the eye can see a lit candle
from 30 miles away

I don't believe this.

I double-checked some other sites and the claims range from one mile to 30 miles. I think I can explain the discrepancy as follows: the more spectacular measurements are probably made ex vivo using frog rods or such. I doubt that you'd want to try to measure downstream of the visual cortex. The "firing" of the rods would of course be most impressive when measured directly. At what level a rod fires, then, would depend quite a lot on how you interpret the statistics.

But: whether it's one mile or 30 really is moot: the brain probably filters out most of the noise (we don't see noisy images at all even in low light, a big difference between the eye and recording media like film).

The other stuff on that site, well, what can I say, it's obviously not written with a scientist in mind. That said, the eye is one of the very most spectacular things, and there is still quite a lot of research in progress to try to understand the physiology and psychology and the image processing.

Regarding their comment on depth perception, obviously having two eyes is the key and comparison to a single camera isn't useful. We all know about stereo cameras...

Anyway this is getting off topic. My point was simply that the dark-adapted eye is waaaay more sensitive than one might expect. Naturally, when I started using my darkroom, I did some tests... and no fog. Even though I could see my feet clearly (albeit after ~20 mins or so). Maybe my eyes are a bit more sensitive than most... there is quite a lot of variation there depending on age and eye colour. When I leave my darkroom, it is really quite painful. I got in the habit of taking sunglasses in with me and turning on lights slowly, one by one.

RalphLambrecht · Jan 11, 2010

iman said:
...

The tacomaeyecarecenter.com site has many errors in their "facts":

1. " * The eye adjusts to 10-billion fold changes in
brightness adjusting for daylight and the dimmest
moon light"

The eye adjusts to luminance, not brightness. Luminance is a measure of intensity. Brightness is a psychological sensation, so the statement makes no sense. Also, the luminance range is more like 10's to 100's of millions, not 10 billion...

I researched numerous papers and books on this subject and never found a totally consistent answer, but most agree on the following:

The luminance range of the human eye is a combination of capabilities:

1. iris 16:1 or 4 stops
2. retina (static) 60:1 or 6 stops
3. retina (dynamic) 1,000,000:1 or 20 stops

This totals roughly 1,000,000,000:1 or 30 stops. Not 10 billion but 1 billion!

iman said:
...

3. * On a clear dark night the eye can see a lit candle
from 30 miles away

I don't believe this.

You don't have to believe it, you can calculate it. If you can see an x-candela star from millions of light years away, from how far away can you see one candela? Now reduce this distance for atmospheric disturbances and... I'm too lazy to do it tonight.

RalphLambrecht · Jan 11, 2010

keithwms said:
Put it in your book, I won't charge much commission

Only if you deliver the sound track!

keithwms · Jan 11, 2010

RalphLambrecht said:
Only if you deliver the sound track!

Maybe Cheryl will collaborate....

(there was a url link here which no longer exists)

JBrunner · Jan 11, 2010

With the safelights out a darkroom should be dark, as in no light. In practice this may be difficult to achieve, which is why we have safelight checks. If you run a thorough check with pre-flashed paper and get no fogging results you are good to go. If you process sheet film, you should do the same kind of pre-flashed test with a sheet of your film in your local "total" darkness. Roll films can be loaded in a bag, or just run a test with a snip if you don't use a bag and examine the neg with a loupe. For certain results, test every kind of paper you use. They have different thresholds. Pretty simple in practice. Lots of fun though in the abstract.

Ian Grant · Jan 11, 2010

Well put Jason, the amount of light needed to begin to fog a roll of 400 ISO film is very low so if your eyes spot light a minute or so after you turn the lights out trace the leaks and fix them.

If you want to process 3200 ISO films then you really do need total black-out, which is usually not that difficult to achieve.

Ian

Mahler_one · Jan 11, 2010

Interesting Jason.....do you think that the light from a Gralab timer can fog film or paper?

JBrunner · Jan 11, 2010

Not in my experience, but my timer is out of line of sight (on a shelf with a lip above my trays). Exposure comes from both duration and intensity, so general speculations about abstract sources and situations aren't really useful.

Testing is they key.

Ian Grant · Jan 11, 2010

Light from timers can and will fog films, and I've seen them fog colour papers.

A friend couldn't eliminate a very slight greenish cast when he began RA-4 printing, it was a tiny red LED on a timer that was the culprit. B&W paper is far more forgiving.

Ian

Mahler_one · Jan 11, 2010

Another question Jason...the point regarding light in the darkroom also involves where the light is coming from. IF the light is coming in from the bottom of the door, and is rather faint....since light travels in a straight line, if the light is not bouncing off of anything bright, how can such light affect film on a table some feet above and to the side of the bottom of the door? I agree that total darkness is to be preferred, but nevertheless, it appears that since light does travel in a straight line that the risk of fogging film above the light leak should be rather minimal, or zero. I also agree that tests might be done to be certain. Not debating that Ralph's method of sealing light leaks can relatively easily be accomplished....however, some here have pointed out that minimal light leaks have NOT affected their work, such work having been carried out in the same darkroom for many years. Those individuals find no compelling reason to change the design of their work space-and one would, it seems, have to accept their opinions. Obviously no absolute right and wrong with reference to the discussion at hand....if it "ain't broke, why fix it"?

keithwms · Jan 11, 2010

Inverse square law. When people say some timer light is fogging their paper, the first thing to ask is where the timer is placed. If it's sitting on the paper then, well, duh.

JBrunner · Jan 11, 2010

Mahler_one said:
Another question Jason...the point regarding light in the darkroom also involves where the light is coming from. IF the light is coming in from the bottom of the door, and is rather faint....since light travels in a straight line, if the light is not bouncing off of anything bright, how can such light affect film on a table some feet above and to the side of the bottom of the door? I agree that total darkness is to be preferred, but nevertheless, it appears that since light does travel in a straight line that the risk of fogging film above the light leak should be rather minimal, or zero. I also agree that tests might be done to be certain. Not debating that Ralph's method of sealing light leaks can relatively easily be accomplished....however, some here have pointed out that minimal light leaks have NOT affected their work, such work having been carried out in the same darkroom for many years. Those individuals find no compelling reason to change the design of their work space-and one would, it seems, have to accept their opinions. Obviously no absolute right and wrong with reference to the discussion at hand....if it "ain't broke, why fix it"?

Again a hypothetical. Too many variables. Even if I was present in the room I couldn't really tell you. Testing is the key. Working in a leaky darkroom and thinking that the leaks have no effect is much different than testing and knowing. Many a print lacks some of the subtle brilliance it could have, particularly in the very highest values, because of that kind of assumption (the assumption that there is no effect), and the photographer doesn't know the difference (perhaps for even for years) because he/she doesn't know the difference, but it can be the difference between a "10" and a print that goes to "11". I can't think of a single reason not to check, except for a lazy contempt for ones own work or sheer hard-headedness.

jp498 · Jan 11, 2010

Mahler_one said:
Another question Jason...the point regarding light in the darkroom also involves where the light is coming from. IF the light is coming in from the bottom of the door, and is rather faint....since light travels in a straight line, if the light is not bouncing off of anything bright, how can such light affect film on a table some feet above and to the side of the bottom of the door? I agree that total darkness is to be preferred, but nevertheless, it appears that since light does travel in a straight line that the risk of fogging film above the light leak should be rather minimal, or zero.

Different Jason.. If you look down, and see light on your floor surface or on your shoes, from the leak at the bottom of the door, then light IS INDEED bouncing up to your eyes, which is further away than the film. Anything you see as illuminated is sending light in your direction.

If you are loading a 35mm roll onto a reel at waist level, the film could be twice as close to the floor as your eye, and gets 4x as much light as your eye, due to the inverse square rule.

Now, I know I can load a roll of iso400 onto a reel and put it in the tank very quickly and won't have any fogging even if light is leaking in. I'm sure I've loaded at least a thousand rolls over two decades. However, I still like it to be really dark. What if I knocked off the table the top of my tank? I could spend several minutes feeling around in the dark for it, and I don't want my film to suffer in the process.

JBrunner · Jan 11, 2010

jp498 said:
...Now, I know I can load a roll of iso400 onto a reel and put it in the tank very quickly and won't have any fogging even if light is leaking in...

Seriously, how do you know? Have you checked? Or is it just something you are printing through without knowing it is there? Film is less critical about overall fog because you can print through it, having a base+fog level to begin with even under perfect circumstance, so my real point is directed towards printing, but this "snip" I have inflicted on Jason's post (apologies) illustrates my point quite well.

Nice to see another Jason!

Sirius Glass · Jan 11, 2010

RalphLambrecht said:
I researched numerous papers and books on this subject and never found a totally consistent answer, but most agree on the following:

The luminance range of the human eye is a combination of capabilities:

1. iris 16:1 or 4 stops
2. retina (static) 60:1 or 6 stops
3. retina (dynamic) 1,000,000:1 or 20 stops

This totals roughly 1,000,000,000:1 or 30 stops. Not 10 billion but 1 billion!

You don't have to believe it, you can calculate it. If you can see an x-candela star from millions of light years away, from how far away can you see one candela? Now reduce this distance for atmospheric disturbances and... I'm too lazy to do it tonight.

More more for the list.

If the number of rods and cones were increased in our eyes, we would not see any better because the evolution of the resolution of the eye stopped when the evolution got to the diffraction limit of the eye.

Steve

RalphLambrecht · Jan 12, 2010

Sirius Glass said:
More more for the list.

If the number of rods and cones were increased in our eyes, we would not see any better because the evolution of the resolution of the eye stopped when the evolution got to the diffraction limit of the eye.

Steve

Not sure about that.

More cones might help. I don't think my eyes are diffraction limited at f/2.

Not that I'm complaining or arguing with my maker, but...

keithwms · Jan 12, 2010

I don't see what diffraction limit has to do with light sensitivity nor the number of receptors. the receptors aren't close-packed in a Bayer grid or something, they have an unusual distribution (hence blind spots). What we see and how sensitively we see it depends very much on the angle at which we look. E.g. optimal scotopic sensitivity is not head-on, this is well known to observational astronomers.

Now, there is a correlation between the diffraction limit and the size of the photoreceptors in the eye: different animals have different sized receptors. But the spectral sensitivity of the individual receptors... the quantum efficiency, if you will.... is a different topic.

fotch · Jan 12, 2010

If Black is perfect, why accept less?

I can understand that some situations are near impossible to solve however, in that case, a person has to accept the fact that it may or may not be a problem is some or all cases.

But, if its something a person and control, why not see the light and block it out? To me, this is part of the fun of making ones darkroom, a challenge to my ability.

WolfTales · Jan 12, 2010

It should be just as dark as the deleted post has been deleted.

Ian Grant · Jan 12, 2010

Don't waste too much time the OP decided APUG's answer's weren't good enough and is now looking elsewhere

Ian

How dark should a darkroom be?

AFlood

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iman

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