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Thread: The perfect white balance - feedback requested

  1. #21
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    I'm not sure that you can compare the luminance of an LCD screen to a laser beam in air... You'd need to know exactly how much light was entering the pupil, which is a function of laser power, fog density, etc... That would be one tough calculation! My guess is that the eye receives more light from the LCD panel than it does from a beam in the air. (Provided the beam doesn't actually enter the eye of course!)

    I do believe, however, that you can maintain at least partial mesopic vision in a dark room even with an LCD monitor on in front of you. So certainly in the case of a laser show in a dark room, the color perception is going to shift towards blue. How much is the $64,000 question...

    I completely agree that this complicates things tremendously. Perhaps we need to collect some empirical data on color balance under various lighting conditions.?.

    Adam

  2. #22
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    We can look at background luminance instead. My book (the science of color) states that "With reduction in retinal illuminance, color matches continue to hold as low as 1 td". Assuming a pupil size of 7mm (seems to be a popular assumption here), that means 1 td (troland) corresponds to a luminance of 0.026 cd/mē. Compare that to moonlight having an ambient luminance level of 0.1 cd/mē. I'd say the luminance is always higher than this in a laser show, especially considering the (bright) laser light covers a large part of your field of vision.

  3. #23
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    Cool

    Wait... So you're saying that under moonlight-only lighting conditions, vision continues to be photopic? I don't believe that - based purely upon my own experience.

    Something is wrong here. Moonlight is dim enough that you're *clearly* into the mesopic vision range. In fact, it's pretty close to scotopic vision. (You can test this yourself.) There's got to be a zero or two missing somewhere!

    Adam

  4. #24
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    I just got home from Qlimax now and it was nice seeing Hugo playing with his pretty lasers. The setup, from what I gather, was 1x 15W Jenlas white, 2x white OPSL (5W?) and 18x 5W OPSL green! Watching those can even make grown men cry.

    Oh, and here's a reminder not to trust cameras the slightest when it comes to laser color representation. These two whites looked nearly identical to my eye. 15W RGB Jenlas in the middle and 5W YB OPSL to the left.

    And according to this camera the satellites have a white that nearly looks like argon: http://uk.youtube.com/watch?v=pr2h7-QUnCY


    Something I reacted on though was that the Jenlas white which is supposed to be so good didn't look all that white to me. They were missing some blue (and maybe green) to make it to a nice D50 or D65 white.

    Now, in the case of the OPSL lasers I can test it against my model. I can assume that they are 2W at 460nm and 3W at 577nm (since those are the only Taipans coherent make). The model predicts that this mixture will produce a slightly red white (x,y: 0.36, 0.33) using Judd-Vos, which is exactly what I thought when I saw them. It should be noted though, that using these OPSL lasers it is impossible to get white as the line between the individual colors does not pass through white in the CIE diagram.

    Quote Originally Posted by buffo
    Wait... So you're saying that under moonlight-only lighting conditions, vision continues to be photopic? I don't believe that - based purely upon my own experience.

    Something is wrong here. Moonlight is dim enough that you're *clearly* into the mesopic vision range. In fact, it's pretty close to scotopic vision. (You can test this yourself.) There's got to be a zero or two missing somewhere!
    I was not saying that vision is photopic under moonlight conditions, but rather that you can still use the color matching functions at such low light levels. That is at least how I interpreted the text. Moonlight is probably indeed in the mesopic range, but perhaps without much change to color perception. I don't find it completely unreasonable to think that big differences in color representation present themselves only at the lower end of mesopic vision.

    I still think that laser light under typical show conditions isomerize an overwhelmingly large portion of our rods quickly and given their slow regeneration compared to cones I believe that the color matches do hold to a sufficiently high degree. Of course there are deviations, but are they big enough? I suspect for example genetic variations play a larger role.

    One way to test it would be to deliberately exhaust your rods with a flash/strobe pulse in the middle of a show and see if you think the beams have different colors before and after the flash.

  5. #25
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    Quote Originally Posted by tocket View Post
    One way to test it would be to deliberately exhaust your rods with a flash/strobe pulse in the middle of a show and see if you think the beams have different colors before and after the flash.
    Or turn the room lights on and then back off...

    Sounds like a fairly easy experiment to perform. When my back is feeling better I'll have to hook up the projector and do some tests at night...

    But I have already experienced different white balance levels previously, simply by training the Pangolin color balance wizard in a brightly-lit room verses a dark one and saving it as a separate pallete. If you load the wrong pallete, the color shift in the white is immediately apparent.

    Adam

    PS: Awesome pic, BTW. Would have been great to see that show in person!

  6. #26
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    Quote Originally Posted by buffo View Post
    PS: Awesome pic, BTW. Would have been great to see that show in person!










    ( All pics: http://www.q-dance.nl/main.php?pid=6...7ef8b372f8f21e )

  7. #27
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    They could have killed people!!! (with joy)

    Wow.




    WOW!

    -Jonathan

  8. #28
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    Wow... just - WOW!

    Those pictures are insane. They should be filed under "lasergasm"! Truly awesome stuff.

    Adam

  9. #29
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    Default amazing

    was this a hugo show? he seems to do the best laser shows and has done q dance before. im guessing this was qlimax. i would love to go to a q-dance event as the lasers are always amazing.


    i think i just got a little over excited looking at those pictures and need to go change lol

    i love lasers when they behave

    ollie

  10. #30
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    Yep, it was Hugo behind the sticks at this Qlimax. It was interesting to see how he works. He is incredibly relaxed and even had time to untie the bikini string of some random hot chick sitting on the rail in the middle of the show.

    Since I managed to hurt my knee sometime around 4 am I spent the rest of the night just watching Hugo and his lasers. I gave him his own little round of applause at the end of the event and shook his hand.

    Here is Hugo's opinion regarding the safety of audience scanning btw (but let's not get into that discussion again).
    Attached Thumbnails Attached Thumbnails hugo.jpg  


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