So I am starting this thread to share an effect I came across on a film I shot recently. We were doing a campfire scene, and as we got more and more into the closeups, I started to light with actual fire more and more.
The obvious bit I found-lighting with fire can be a hell of a lot of fun! Either having someone squeeze lighter fluid on the fire, or placing a coke can with the top cut off, half full of fluid really gives you the feeling of fire. Of course-it is fire.
However there was one thing I could have probably remembered from science class, I didn't discover until the grade: most of fires heat is given off in the form of IR radiation. This causes the reds to saturate, and shift the overall hue of the light.
In wides, I was lighting with 6- 212 & 211's aranged behind the fire, in a triangle made of 20" C-arms. In closeups (especially with our bespecaled charecter) we started going more and more to fire. In the color grade, that led to a VERY saturated red taking over skin tones. I corrected that with a 3deg hue shift, which to me made sense. Afterall, the extra IR would be shifting the hue outside of the visible range into the red, so a hue shift would bring it back. I tried doing it on the wheels, but the hue shift felt better to me.
I thought I would pass along that discovery in the hopes that it someday helps someone out. Obviously if you are doing a shot with propane gas and concrete logs, it won't be as big of an issue, since it seems most of the heat of a fire (and thus IR) comes from the coals. But if you are doing a real wood fire, maybe consider adding a hot mirror to the camera package. I would have never thought to include that in the package, but I think from now on, if I see fire as a major light source, I will be using a hot mirror.
I can't post pictures until the film comes out, unfortunately, but maybe once it does I can share some before and after grabs.