Scriming lights

[Noel Evans]

Other things can also effect your light output such as bulb age for example. Best way to be sure that light A is putting out equivalent to light B in any given situation is by light meter I realise thats not helpful as you said without calculating on a light meter.

Another way would be to point your cam at a white wall with the light head and use a waveform to read the ire. And then swap lights and do the reading on the second unit / make changes until they match ire level.

[DDirector]

Full/Double scrim = 1 stop
Half/Single scrim - 1/2 stop

Full/Double scrim (1-stop) [Half the light]
1,000w = 500w

Half/Single scrim (1/2-stop) [Quarter of the light]
1000w = 750wSo, if Im adding a gel to it;
1000w + Full CTB (1-stop) = 500w
1000w + 1/4 CTB (1/4-stop) = 750w

Everything right?

[Bern Caughey]

In practice Full CTB reduces the intensity closer to 1.7 stops of light. Often 2.

[Moseph]

1/4 CTB cuts the light by a little over half a stop too. Quarter, half, and full don't correspond to the F stop reduction, it's solely the color temperature change.

[DDirector]

Oh. Good you pointed that out. thanks
I know it wasnt related to f-stops, but I thought that it might have been roughly the same.

[DDirector]

So, CTB is roughly 2x the amount stated:

1/4 CTB = approx 1/2-stop
1/2 CTB = approx 1-stop
1 CTB = approx 2-stops

what about CTO gel?
how much light loose would it be? if its possible to calculate.

1/4CTO =
1/2 CTO =
3/4 CTO =
1 CTO =

[David G. Smith]

From "Motion Picture and Video Lighting" By Blain Brown.

Conversion factor and light loss.jpg

[DDirector]

Awesome!