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  1. #51

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    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
    Last edited by AFlood; 01-11-2010 at 07:10 AM. Click to view previous post history.

  2. #52
    keithwms's Avatar
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    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....
    "Only dead fish follow the stream"

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  3. #53
    RalphLambrecht's Avatar
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    I feel flattered. Nobody has ever dedicated a song to me before.

    I'll frame this!

    Thanks you, so much.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  4. #54
    keithwms's Avatar
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    Put it in your book, I won't charge much commission
    "Only dead fish follow the stream"

    [APUG Portfolio] [APUG Blog] [Website]

  5. #55

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    Quote Originally Posted by keithwms View Post
    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.

  6. #56
    keithwms's Avatar
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    Quote Originally Posted by iman View Post
    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.
    "Only dead fish follow the stream"

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  7. #57
    RalphLambrecht's Avatar
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    Quote Originally Posted by iman View Post
    ...

    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!

    Quote Originally Posted by iman View Post
    ...

    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.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  8. #58
    RalphLambrecht's Avatar
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    Quote Originally Posted by keithwms View Post
    Put it in your book, I won't charge much commission
    Only if you deliver the sound track!
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  9. #59
    keithwms's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    Only if you deliver the sound track!
    Maybe Cheryl will collaborate....

    http://www.apug.org/forums/forum47/6...your-week.html
    "Only dead fish follow the stream"

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  10. #60
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    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.
    Last edited by JBrunner; 01-11-2010 at 12:07 PM. Click to view previous post history.



 

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