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  1. #11
    JBrunner's Avatar
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    Quote Originally Posted by Matthew Rolfe View Post
    Thanks for your replies.

    ...So reducing the power input by using an extension cord will in turn reduce the Kelvin output?
    Yes, in the case of a bulb that uses a filament. The addition of distance and connections has the effect of lowering the voltage to the filament. It burns less bright and at a lower color temp. Most studios I work in are supposed burn 3200K, but meter in at about a real world temp of 28-2900K because of the voltage drop (caused by resistance) associated with the cables and connectors. Since the drop is more or less uniform, we tend to ignore it.

    The standard Hollywood gels for color correction are CTB (towards blue) and CTO (towards orange). They come in grades 1/8, 1/4, 1/2, and "Full" from both Lee and Rosco. Full CTB will correct 3200 to about 5500 (with a 70% or so loss of transmission) or vice versa for full CTO (with a 20% or so loss of transmission). The blue filters tend to suffer from fading (because they absorb a lot of energy) unless of the highest quality (like from Lee or Rosco).

    CTB and CTO stand for "color temperature blue" and "color temperature orange" respectively.
    Last edited by JBrunner; 03-03-2010 at 12:04 PM. Click to view previous post history.

  2. #12

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    Thanks for the help. I have a couple of 3400k bulbs that are 500 watt so I will use a filter to bring them nearer to 5000k, like you suggest. With two bulbs at 500 watt each I can afford to lose some light transmission.

    Thanks both of you for clearing up some confusion.

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