How do i figure out which amount of CTB/CTO gels i need for correction?

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N3D

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Im currently in the pre production of shooting a horror webseries.


I want to hire 3 dedos. And also use practical indoor lights/lamps.


I also have two cheap soft boxes and a cheap Chinese lantern (china ball)


If i white balance to the indoor lights to trick the camera into making it look white. Im guessing the dedos will become too blue? How do i figure out which amount of CTO i need? Quarter, half or full? Or does it not make a difference.


E.g using a FULL CTO will always give me a FULL CTO light even if i dim the dedos?


Also a quick question, i always get harsh shadows from dedos. How do i get rid of or balance them out? Would a soft china ball light do the trick by acting out as a fill/ ambient light? I wouldn't want to soften the dedo i like the hard light effect.


Thanks for your help.


Ned.
 
What are you using for indoor lights that you think the Dedos will be blue in comparison to? At their peak they're around 3200K, which is really quite orange, and the more you dim them, the redder they get.
 
Very few people actually bother correcting a light back to 3200k after dimming them in my experience. If maintaining the color temperature is important, use ND gel or scrims.
 
David Jimerson said:
What are you using for indoor lights that you think the Dedos will be blue in comparison to?

(And the more you dim them, the redder they get.)
Click to expand...
I'll be using incandescent bulbs on lamps for practical ambient/background lighting. Which i will white balance (i don't want a warm look).

I'm worried the Dedo's wont match especially when dimmed. I want them to match the practical lights.

Also there is a chance i will use soft boxes (fluorescent energy saving daylight bulbs), i also will need them to match.

Here is a rough light plan. It might help. rough light plan.jpg

Thank you guys, once again.

Ned.
 

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The Dedos most likely won't mismatch significantly from the normal indoor incandescent lighting, and they certainly won't look blue. There won't be a need for CTO.

If you have daylight-balanced fluos in the mix, then you probably will need CTOs for those.
 
Generally you are asking how much filtration is needed to bring one light source to the same color temperature as a second source. There is a mired shift calculation you can perform to determine that, or use the handy Lee Filter calculator.There should be a wikipedia article on mired as well if you're interested.
 
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Dedos are not really up to the task of what you are doing here. (lighting plan).

What are they rated 100, 150 watts? (Mine are 150)

Usual method of determining CT is by measuring light with a CT Meter and making the calculation for the relevant CTO GEL to be used.

A broad brush stroke approach of 1/4, 1/2 and full correction is usually enough to get away with. (eye-ometer)

BTW - dont be afraid of mixing color temps ("fruit salad") if it suits the "story/scene"
 
Shooter said:
Dedos are not really up to the task of what you are doing here. (lighting plan).

What are they rated 100, 150 watts? (Mine are 150)

Usual method of determining CT is by measuring light with a CT Meter and making the calculation for the relevant CTO GEL to be used.

A broad brush stroke approach of 1/4, 1/2 and full correction is usually enough to get away with. (eye-ometer)

BTW - dont be afraid of mixing color temps ("fruit salad") if it suits the "story/scene"
Click to expand...
So which lights do you think will work better? Keep in mind thats it is a very small apartment and it will be crowded (cast and crew)

Does that mean i have to buy a load of 1/4, 1/2 and full gels and work it out by eye on the location durin shoot? Or do i just buy several fulls?

Thanks again, you guys are pretty awesome!
 
What they are saying, is that if you go with your plan and use pracicals and Dedos, you wont need any gels to correct the lights. All these lamps are approximately the same colour temperature.
 
if all your pracs are incandescent they will match the dedos (100w or 150w)
the softbox with daylight flos will have to be convertrd to 3200 with cto

if the dedos go too orange when dimmed you can put some 1/8 ctb on them but i shouldnt think
this will be necessary.

full cto converts 5600 to 3200k
half cto 5600 to 3800k
1/4 cto 5600 to 4600k
also available in 1/8

full ctb converts 3200 to 5700k
3/4 ctb 3200 to 5000k
1/2 ctb 3200 to 4300k
also available in 1/4 and 1/8

cheers
 
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