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Thread: How to read "K" value of light???

  1. #1
    stradibarrius stradibarrius's Avatar
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    How to read "K" value of light???

    Would any of the common "light" meters be able to give the "K" value of the light in a given scene?
    I have just finished a remodel of my violin shop and the "T5" florescent bulbs give off a strange color cast. I have tried adjusting the WB values of my digital camera to see if I could at least get close.
    I was trying to come up with a way of measuring the temperature of the light.
    Generalizations are made because they are Generally true...

  2. #2

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    Re: How to read "K" value of light???

    Minolta used to make a color meter

    spectra and lunasix made one years ago..but they seemed almost impossible to use

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    Re: How to read "K" value of light???

    LuxMeter Pro on my iPhone reads it. Don't know ho precisely though with a discontinuous spectrum source like yours.

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    Peter De Smidt's Avatar
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    Re: How to read "K" value of light???

    These days florescent bulbs are all over the place. You can use something like a Whibal, if you're shooting raw, and white balance in post. Or you can use something like this: http://www.bhphotovideo.com/c/produc...ance_Lens.html , and do a custom white balance in camera. I do the latter when I have to video judo tournaments with my dslr.
    "Why can't we all just get along?" President Dale, Mars Attacks

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    I live in Connecticut now.
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    Re: How to read "K" value of light???

    They do make an "FL" filter, specifically for Florescent lighting, in most cases that should do it, unless you are trying to balance that with tungsten bulbs on the wall or sunlight coming through an uncoated window.

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    Peter De Smidt's Avatar
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    Re: How to read "K" value of light???

    The "FL" filter isn't very effective anymore, due to the bewildering array of different fluorescent lights. With some commercial interiors I shoot, the color values of the light fixtures will vary all over the place, as the maintenance people apparently buy whatever is cheapest, or whatever they just happen to grab that day.
    "Why can't we all just get along?" President Dale, Mars Attacks

  7. #7

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    Re: How to read "K" value of light???

    Quote Originally Posted by StoneNYC View Post
    They do make an "FL" filter, specifically for Florescent lighting, in most cases that should do it, unless you are trying to balance that with tungsten bulbs on the wall or sunlight coming through an uncoated window.
    That will work for some daylight fluorescents but not with all. Each filter manufacturer that makes or made FL filters made them to correct what they felt was the "average" FL correction. But if you have different FL tubes then they made the filter for or if you have a mix of different daylight tubes then the filter may not help you at all. But another manufactures FL OR F Day might be better. BTW FL is a Tiffen trademark and when we were the B+W distributor Tiffen sent us a cease and desist letter and we had to have our designation changed to F Day. Also with Heliopan's version. Ran into the same problem with Heliopan's High Transmission polarizer reps. Turned out the High Transmission is a Trademark of Tiffen's also. So we had to have the factory change to HT on the filters.

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    I live in Connecticut now.
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    Re: How to read "K" value of light???

    Quote Originally Posted by Bob Salomon View Post
    That will work for some daylight fluorescents but not with all. Each filter manufacturer that makes or made FL filters made them to correct what they felt was the "average" FL correction. But if you have different FL tubes then they made the filter for or if you have a mix of different daylight tubes then the filter may not help you at all. But another manufactures FL OR F Day might be better. BTW FL is a Tiffen trademark and when we were the B+W distributor Tiffen sent us a cease and desist letter and we had to have our designation changed to F Day. Also with Heliopan's version. Ran into the same problem with Heliopan's High Transmission polarizer reps. Turned out the High Transmission is a Trademark of Tiffen's also. So we had to have the factory change to HT on the filters.
    I suppose that makes sense, and using the color meter to read the scene obviously would be best, I know that in the movie industry they just bring their own bulbs and if they ever shoot in at normal location that has fluorescent lighting, they will swap out every single bulb in the entire room with their special bulbs that are the right color tone, and then when they're done for the day they will remove those and replace them with the bulbs that existed before hand, but I figured for all intents and purposes the FL (or F-Day) filter was better than nothing, and a lot cheaper than getting tons of color accurate bulbs or buying an expensive color meter and tons of various temperature filters, the OP doesn't sound like they are looking to go crazy here, but I could be wrong.

  9. #9
    Drew Wiley
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    Re: How to read "K" value of light???

    Even the best color temp meters only work so-so with fluorescent lamps because these have a discontinuous spectrum. High CRI bulbs are less obnoxious than the usual el cheapo commercial varieties. Meters just read peak sensitivities corresponding to the specific three in the film itself. You can make advance film and printing tests, but don't expect good results. Those silly various purple-amber fluorescent filters do work OK for old-school cool white bulbs, just OK. Any quality
    shot requires you either bringing in your own lighting or resorting to black and white film.

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    Re: How to read "K" value of light???

    Quote Originally Posted by DrTang View Post
    Minolta used to make a color meter
    +1 and they work very well even after all these years. L

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