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  1. #11
    Willie Jan's Avatar
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    I bought a led strip and put it on the ceiling (4 meter high) bouncing back.

    I preflashed the paper for getting a 18% gray. After that put it at the place where the develop tray is positioned. put some coins on the paper and leave it for 10 minutes.
    after that develop normally.

    I see that the paper is fogged. The place where the coins where are more white than the rest. This means the red strip is not darkroom save!

    Now I wonder how you guys tested it?
    Did you also preflash the paper? I would check this the next time you are in the darkroom!!!!!

  2. #12
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    My first red LEDs were 620nm and they were not safe. I use deep red LEDs (~660nm) and don't have anymore problem now.

  3. #13
    Willie Jan's Avatar
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    do you have some specs for these deep red lights?

    At ebay they all come from china and mention Yes back....

  4. #14

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    I preflashed the paper, but did the test with it on the enlarger easel. The distance is about the same as my developer area though.

    I bought the LED strip at a home center, no longer have the box it came in, but I'll look at the strip and see if there is a manufacturer name or some other indication of the LED source.

  5. #15
    stormpetrel's Avatar
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    You will find all the information here.

    http://www.apug.org/forums/groups/sm...room-lamp.html

    By the way, the first LEDs I used were centered on 620nm. The spectrum of LED is not a single wavelength like lasers have but a bell shape curve. The 620nm LED emitted enough energy under 600nm which fogged the paper. 600nm is the safe limit recommended by paper manufacturers in their datasheet.

    Then I went with high power 700nm LEDs which were the first high power deep red LEDs available on the market. They were very safe indeed but I could hardly see anything in the darkroom (only 20% of the light was visible)!
    One year after, high power 660nm LEDs were available and those are perfect for darkroom usage.

    I have opted for a design you could adjust the intensity which is a very nice feature when you work long hours in the darkroom.

  6. #16

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    Quote Originally Posted by stormpetrel View Post
    ......By the way, the first LEDs I used were centered on 620nm. The spectrum of LED is not a single wavelength like lasers have but a bell shape curve. The 620nm LED emitted enough energy under 600nm which fogged the paper. 600nm is the safe limit recommended by paper manufacturers in their datasheet.

    Then I went with high power 700nm LEDs which were the first high power deep red LEDs available on the market. They were very safe indeed but I could hardly see anything in the darkroom (only 20% of the light was visible)!
    One year after, high power 660nm LEDs were available and those are perfect for darkroom usage.

    I have opted for a design you could adjust the intensity which is a very nice feature when you work long hours in the darkroom.
    I've had a similar experience. Note that the published spectrum graphs of LEDs have the vertical axis in arithmetic units, not exposure units that we are used to. This means that the spread is worse than it looks in the graph.

    I also have variable intensity, very useful. Also, I have read (don't remember where) that the spectral spread of LEDs is smaller when they are working at lower currents.

    Also, I made a hand held light with 4 yellow-orange LEDs that I use to check paper near the end of development. Those LEDs are not safe enough for normal darkroom illumination, but quite safe for a short look. It's a relief to see the image in yellow-orange light after being accustomed to 660nm red!

  7. #17
    stormpetrel's Avatar
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    Yes indeed. The photons emitted on each end of the LED emission spectrum become negligible so it is like narrowing the spectrum of the LED.

  8. #18

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    I've never read one of these LED red safelight threads that inspired confidence.

  9. #19

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    Click image for larger version. 

Name:	LED4D_AllLED_Spectra.jpg 
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    Since B&W paper is blind to anything over 550nM, lots of color choices available. I like the "Thomas" yellow color but using one in my darkroom with a low ceiling does'nt work. Amber/yellow Christmas LED string works for me. To test, I placed a paper and coins on the counter and left it there, untouched for 30 minutes. Developed in Ethol LPD for 3 minutes, stop, fixed and washed. No visable evidence of fog. I don't know about the "flash" method of testing if that would have an effect or not.
    Gun Control is like: Reducing drunk driving by making it harder for SOBER people to buy cars.

  10. #20
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    Believe it or not, Walmart sells bulbs called "party bulbs" which come in red, green, yellow etc. The red ones work spectacularly well. I have mine in 6" aluminum reflectors with spring clamps and plig them right into my timers..about a $10 or so imvestment.

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