When adding a flavor of color theatrical gel what is the best practice when being cautious of white balance?
Ex.
Say I'm using an odd HMI lamp as the key and it's reading 5400K via a sekonic c-500 meter.
The desired White Balance is... lets say 3200. My pCam app says the the mired shift is 127.
I toss a Rosco 3401 Sun 85 gel or perhaps a 3/4 CTO gel to get me mostly there (either gel is rated at 131 mired)
Great... but now the art director/dp/client/boss says they want the light to be green...?
Do I then add a green filter on top of that... ...or do a magic trick w/ thinking of green as being somewhere around 4500K and use just one gel to accomplish the shift from 5400K. Using just one gel I imagine should reduce light loss. So once again back at the pCam app and it says the mired shift from 5400 to 4500K is 37... ...so am I right in thinking i should just throw on a 1/4 CTO? If so, how do I control the density of the green - add/sub green gels?
What about if they say they want the color to be purple, red or even yellow?
If there is a common consensus in terms of methodology, please let me know. I'd prefer not re-invent the wheel or get dumb looks from crew. It's very possible this may have already been explained to me in a lecture, but my taxed brain was overloaded.
I am by no means a pro (I'm a part-time film student working a full time day job).
Thank you for taking the time to read all of this.
I recently made a scene remake from Blade Runner using the school's only HMI light graciously received as a donation from DTC w/ mixed tungsten lamps and got a bit of a headache trying wrap my brains around gels for both correction and color: http://vimeo.com/nextbooth/blade
Awesome info, thank you Stuart! What is the common practice for measuring the Green/Magenta axis and knowing the amount of CC gel to use? In terms of color tools I have a Sekonic C-500 color meter, pCam iphone app and the SMPTE one shot color chart. I'm trying to nail down controlling color on the fly as much as possible during principal photography.