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  1. #21
    Photo Engineer's Avatar
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    Kodak Endura paper was designed with sensitivity to match the output from a tungsten light with a WR 13 over it. The peak and dip were complimentary. This does not apply to Fuji papers AFAIK.

    The WR 13 can be used continuously with an indirect illumination using a 15 watt bulb. I use 2 in my darkroom pointed away from my work area and they are quite bright after just a short time.

    I have never, in over 30 years, fogged a sheet of color paper by that means.

    PE

  2. #22

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    Quote Originally Posted by Photo Engineer View Post
    This does not apply to Fuji papers AFAIK.
    I've never had any problems using a #13 safe light with Fuji color paper.

    Quote Originally Posted by Fotohuis View Post
    A sodium lightsource (590nm) has a bandwith of about 6nm, a mercury lightsource 254nm often used in the spectroscopy also such a small bandwith.
    Exactly what type of sodium lamp are you referring to? Are you sure you're not talking about nominal output rather than actual/total output? If the output bandwidth of a sodium lamp was that narrow, you wouldn't be able to distinguish colors at all in a room lit with a sodium lamp. I assume you're talking about high pressure sodium, but even with low pressure sodium, you can distinguish colors. The same with mercury vapor lighting. I don't know of any unfiltered light source except for a laser that would produce a spectrum bandwidth as narrow as 6nm.

  3. #23
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    Regarding Fuji papers, I did not mean to imply that it would not work at all, but rather that the Kodak papers were specifically designed with that safelight in mind, and vice versa. The Fuji papers may not have exactly that same dye for sensitization.

    PE

  4. #24

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    Quote Originally Posted by max_ebb View Post
    I've never had any problems using a #13 safe light with Fuji color paper.

    Exactly what type of sodium lamp are you referring to? Are you sure you're not talking about nominal output rather than actual/total output? If the output bandwidth of a sodium lamp was that narrow, you wouldn't be able to distinguish colors at all in a room lit with a sodium lamp. I assume you're talking about high pressure sodium, but even with low pressure sodium, you can distinguish colors. The same with mercury vapor lighting. I don't know of any unfiltered light source except for a laser that would produce a spectrum bandwidth as narrow as 6nm.

    Low pressure sodium vapor lamps use the sodium doublet transitions at 589.0 & 589.59 nM, and are extremely monochromatic. Only when impurities are added -- Doping -- will you see other electron transitions. :o

    If you go to San Diego, you'll see that all of the street lights are low pressure sodium vapor, installed at the behest of the Mount Palomar Observatory: The "city lights" essentially ruined the southern view of their telescopes; but when the LPS bulbs & fixtures were used, they could easily filter out the monochromatic light contamination.

    High pressure sodium vapor lights also use other electron transitions from the intentional doping; and some even use the very efficient 389 nM near-UV mercury transition, which excites phosphors in the tube much like a conventional fluorescent tube.

    -------

    In any case, although the sodium doublet transition as leveraged in a low pressure sodium vapor lamp is highly efficient, yielding (IIRC) ~140 lumens per watt, it is not favored by illumination engineers because of the very monochromicity which makes it desireable for an RA-4 safelight.

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