Using red led strips in the darkroom

Discussion in 'Darkroom Equipment' started by Willie Jan, Feb 22, 2014.

  1. Willie Jan

    Willie Jan Member

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    Is someone using led strips in the darkroom?

    I saw somewhere that they were using a led strip, but wondered if this is possible without fogging paper.
    The red leds offered at ebay should be between 600-720 nanometer.
     
  2. David Brown

    David Brown Subscriber

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  3. bdial

    bdial Subscriber

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    I bought a 3 color LED light strip to try out and experiment with. I don't care for the character of the "white" light it provides, but using it with just the red LEDs for safe lighting is working out very well. (I was hoping for lighting that could be white and safe in one).

    I tested it up to 15 minutes with no fogging, it's very bright, and the remote allows you to dim it in any color.

    The product I bought is this one, or similar to it;
    http://www.homedepot.com/p/Commerci...ote-DC5237WH-A/204087512?N=5yc1vZc7phZ1z115g2
     
  4. konakoa

    konakoa Member

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    I'm using a long strip of red LEDs in mine. They point up and bounce off the ceiling for soft, even illumination. I added a LED dimmer so I could adjust the brightness as well. These red LEDs tested safe out to twenty minutes (I went out to thirty minutes) using the Kodak safelight testing methodology.
     

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  5. grahamp

    grahamp Subscriber

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    I tie my safelights into the enlarger timer, so I would always worry that a mixed colour strip would not come back on as red :cool:
     
  6. Willie Jan

    Willie Jan Member

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    Thanks guys.
     
  7. jumanji

    jumanji Member

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    I cut a 20cm strip and make a crefully test it with some piece of papers, distance from 3m to 30cm, in 45 minutes. After develop and fix, they're still white, so it's absolutely safe! Not only cheap, easy to find, but also much brighter than traditional safelight.
     
  8. Cruzingoose

    Cruzingoose Member

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    Why suffer with red when you can use amber and yellow. I use one string of each streched out the length of the darkroom. Easier to see and no paper fogging at all. Tested for 10 minutes with no fog. It makes it easy when I'm cutting roll paper down to 8x10 sheets.
     
  9. David Brown

    David Brown Subscriber

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    Well, "any" color will work if it tests "safe".


    For some. Some prefer red. YMMV

    I used to have red lights that were not safe in the darkroom for when I needed more light, but didn't want to use the white lights, so that I could retain my "night vision". I learned this from the astronomy folks. (Now with much brighter safelights, I don't do this anymore.)
     
    Last edited by a moderator: Feb 24, 2014
  10. Cruzingoose

    Cruzingoose Member

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    LED Lites

    Any color won't work. Blue and green will most definately expose your paper. Yellow LEDs work better than Low pressure SOX lamp used in the the famous Thomas safe light, known for incredible brightness due to the narrow bandwidth of sodium. But it still required a filter to remove the neon and mercury lines. The LED has a much narrower bandwidth and needs no such filter as its light is very pure. Yellow is also less irratating to the eye as your eye is most sensitive to green. Red is at the end of the range of human vision and thus requires much higher illumination levels to appear the same brightness as yellow. Amber has been the safelight standard for many years and LEDs produce this color very well. It is the second color LEDs were available in the early days. The first was Infrared, then red, amber, yellow, yellow green, then pure green in the mid 90s, followed by blue. There are two violet LEDs out now. One is a blue LED using a red phosphor and a native violet and recently true UV LEDs. White LEDs don't count as they are all blue LEDs with a drop of yellow and/or white phosphor over the die.

    The problem with LEDs, or rather the marketing (profits), is the LED can last forever. Because they are extreemely overdriven they are marketed as having a 20,000 to 50,000 hour life. Heat and overcurrent can destroy and severly shorten the LED lifespan significantly.
     
  11. Willie Jan

    Willie Jan Member

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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!!!!!
     
  12. stormpetrel

    stormpetrel Member

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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.
     
  13. Willie Jan

    Willie Jan Member

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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....
     
  14. bdial

    bdial Subscriber

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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.
     
  15. stormpetrel

    stormpetrel Member

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    You will find all the information here.

    http://www.apug.org/forums/groups/s...41-low-cost-adjustable-red-darkroom-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.
     
  16. john_s

    john_s Subscriber

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    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!
     
  17. stormpetrel

    stormpetrel Member

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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.
     
  18. Tom1956

    Tom1956 Inactive

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

    Cruzingoose Member

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    LED4D_AllLED_Spectra.jpg

    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.
     
  20. eclarke

    eclarke Member

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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.
     
  21. David Brown

    David Brown Subscriber

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    http://www.kodak.com/global/en/consumer/products/techInfo/k4/k4TestSafelite.shtml

    Yes, this involves "flashing" the paper to achieve the very first level of exposure to the white light, so that any additional exposure from the "safe" lights will show up.