Article on color temp meters and filters

Discussion in 'Exposure Discussion' started by bobfowler, Dec 28, 2004.

  1. bobfowler

    bobfowler Subscriber

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    I posted a link in the articles forum to an article I posted on my website about selecting and using color temperature meters and decamired filters. I'd appreciate any feedback and or suggestions.

    Thanks,
     
  2. Helen B

    Helen B Member

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    Bob,

    Some very minor comments on an interesting article:

    How about mentioning the Minolta Colormeter II? There are plenty of them available second-hand for around $200 and they are OK for continuous light.

    You might mention that 3400 K lamps are also known by as P1 and 3200 K as P2. By the way, kelvin is written without a capital K (in accordance with SI convention for the names of units), and the abbreviation is 'K', not '°K'. The SI name for mired is 'reciprocal megakelvin', if it matters.

    One convention that I'm aware of refers to CT and CC filters. CT being the ones for adjusting colour temperature and CC for colour compensation. CC filters are in RGB and CMY only: typical Wratten-style designations are CC20M and CC025R for example. Wratten 80 and 85 series are called 'conversion' filters and the 81 and 82 series are called 'balancing' filters by Kodak.

    With still film I use my colour meter for fluorescent lights more than for incandescent sources - which can often be guessed at quite well. I carry CC10M and CC20M filters - my preference is almost always to under-correct so that the character of the lighting is maintained.

    Your examples of colour temperature of sources doesn't cover practical indoor sources (ie general service lamps). Maybe it would be worth adding approximate values:

    200 W GS lamp: 3000 K
    100 W GS lamp: 2900 K
    60 to 75 W GS lamp: 2800 K
    30 to 40 W GS lamp: 2600 K
    candle: 1400 K

    Passing thought: is it worth mentioning that non-incandescent sources can have a correlated colour temperature?


    Just out of interest, does anyone make Type A tungsten film for still cameras nowadays? As well as mentioning Type F, you may also wish to mention Type G Ektachrome - which was balanced for about 4200 K as I recall, and which is probably still being used because it isn't so long since it was discontinued.

    Best,
    Helen
    PS I'd take issue with you about digital cameras not needing CT or CC filters at all - but that's not for this forum.
     
  3. bobfowler

    bobfowler Subscriber

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    Helen,

    Thanks for taking the time to read, and for your comments. You raise some very good points, and I'll address those in some additional editing!

    My specific mention of CC units was in relation to the Color-Pro 3F, it's one of the 3 ways that meter displays filter values. It does bring up the point though that I should at least draw attention to the other filters besides the decamired series.

    In the next revision, I'll add some more examples and include a few GS lamps.

    Thanks again!
     
  4. Puma

    Puma Member

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    What KR and KB filters do I really need?

    I want to start shooting Velvia 50 RVP (5500) and I want to know what color correction filters I really need to buy? Later I want to learn to use Portra 800 and would prefer to color correct at the time of exposure, what filters do I really need for that?

    Note that I plan to shoot daylight film indoors and outdoors.

    Thank you,

    Puma
     
  5. Greg Davis

    Greg Davis Member

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    An 80A filter will be good for standard tungsten light bulbs. An 80D will be good for most fluorescent bulbs, but it won't correct for the green color, so add CC10M and CC20M filters to your kit. You won't need both CC filters at the same time for most fluorescent bulbs, but some may need it. Take test shots under the conditions you experience most and see what works best for you. There are other filters you can use that fill in the gaps between the light blue (82 filter) and dark blue (80A filter), so you can make small adjustments if needed, but the two I mentioned earlier will get you started.