Double CTB vs Full CTB

iamlance

iamlance

Well-known member
After doing the lighting for a small shoot today, I went home and noticed that what I thought was full ctb was in reality double ctb. I looked up the differences and saw full ctb was for conversion to 5700k photographic daylight and double cto was for conversion to 26000k daylight. We were balancing open-faced tungsten lights with daylight streaming from 10 windows. It looked fine on set and in the camera. The light was not directly shining in the windows and it was in the early afternoon.

As I don't have a color temperature meter, how can I tell when to use one or the other? Is it just guess work, or is there some relation to time of day, overcast/direct sunlight, etc.?
 
I already saw the lee link, which doesn't answer my question. I have the lee filters. I hadn't seen the rosco link, however. It gives a different color temperature conversion (10000k) and says it is just to oversaturate a scene.

So is it to oversaturate a scene (as the rosco link says), or to balance to a higher daylight (as the lee link says)? Or does that overlap? Again, does time of day determine usage?
 
To be honest, it's all subjective.

I usually start with 1/2 CTB when matching daylight coming in through a window depending on the look I'm after.
 
I think you're over thinking this. Certainly it's good to know these technical ins and outs but if it looks fine and everyone is happy with what they see, just roll with it. Double CTB can serve both purposes you mentioned, and time of day / weather does have an effect on when it can be used. If it's cloudy outside or the sun is down and all you're getting is skylight, it's going to be much more blue than when sunlight is in the mix.

That said, even full CTB on a tungsten light in a day interior is extremely rare these days.
 
Yeah, when I was looking this up before posting here, I saw that sometimes people use 1/2 or 3/4 ctb to get a little more light while still keeping it noticeably daylight colored.

I do overthink things sometimes, but once I understand the concept, that goes away. I overthink it because of a lack of understanding.

But thanks for the comments. I'll put them to good use.
 
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