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  1. #21

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    A better safelight filter test

    LED's are wonderful safelights. Simply exposing the paper to the LED radiation for a period of time is not a sufficient test. If you want to be sure the safelight isn't going to degrade your prints you need to conduct a test with paper that you have pre-exposed. By pre-exposing the paper the safelight exposure is on the lower portion of straight-line portion of the D LogE curve ( i.e. Zone III) . In practice fogging increases in these densities BEFORE it increases the true D min.


    Thius is described in:

    http://www.kodak.com/global/en/consu...Safelite.shtml



    Bob Shanebrook
    makingKODAKfilm.com

  2. #22

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    Correct. A proper safelight test is important.

  3. #23
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    Well here's what I can tell you. The red led bulbs from superbrightleds have no fogging issues with any paper I use (ilford, emaks, adox, foma, slavich). If they do I haven't noticed it.
    Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.

    http://www.flickr.com/kediwah

  4. #24
    E76
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    In addition to fog you might always want to check and make sure you don't have any changes in gradation if you're using VC paper. As I recently learned an unsafe safelight will change the grade before it causes any visible fog!

  5. #25

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    Quote Originally Posted by Rafal Lukawiecki View Post
    .......I will try a different make, lower wattage red LED bulb, with and without a standard red safelight filter, some time this month.
    I read somewhere, and I'm sorry I don't remember where, that the wavelength spread of a "monochrome" LED is narrower at lower currents. I'm not able to test it. I have resorted to very red LEDs which I can use at quite a high level without fogging or other effects. I have made several safelights that were not very safe (less extreme red, and also orange).

    I have made a hand-held light with amber LEDs which I use for brief amounts of time when I want better judgement of density, such as preliminary test strips.

  6. #26
    Roger Cole's Avatar
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    For a darkroom 'flashlight" for finding things and such I use my adjustable brightness red LED flashlight I bought and use for astronomy. It does great double duty in the black and white darkroom, and they're cheap:

    http://www.telescope.com/Orion-RedBe...ght/p/5755.uts

    You can get cheaper ones but they generally don't have adjustable brightness and the bright is pretty darned bright. This one goes down to "dim enough" for astronomy at a dark site, which is dimmer than you need in the darkroom. I could read a book easily on the bright setting once eyes are dark adapted (assuming black print on white - red messes heavily with color vision.)
    Last edited by Roger Cole; 07-09-2012 at 12:06 AM. Click to view previous post history.

  7. #27
    Michel Hardy-Vallée's Avatar
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    Amber and RA4

    I just pulled an all-nighter printing RA4 (took months of preparation just to make sure every material was on hand!), and I took the opportunity to test my SuperBrightLED Amber light as a colour safelight.

    The bad news is: it fogs paper. The good news is: just a bit. The light happens to be around the vicinity of the spectral sensitivity hole, so all it gave was a light cyan cast. The way I used the light was to put it in an adjacent locker, leave the door ajar, and work with the indirect light. It seems it was already too much, but not by terribly much.

    I suppose with the weakest LED available, one could put together a safelight that could be useful for quick checks, such as finding your way from the enlarger to the developing tray.

    Still, a safelight is not terribly useful for RA4, since you can pretty much turn on the light once the paper is in the stop or the bleach-fix bath if you process in trays; if you process in tubes, then you don't need a safelight, unless you're really clumsy at assembling the tube.
    Using film since before it was hip.


    "One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution" — Sir John Frederick William Herschel, "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. p. 11

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