What's the big deal with Color Temp?

Note: Color temp figures and conversions were culled from several sources, including  Rosco International

http://www.rosco.com/  

First, Color temp is a bigger deal with film than video, because the film emulsion must match the color temp of the light (indoor/Tungsten 3200k, or  average Outdoor 5,600k*). If it does not then filters have to be added to the camera or the lights to create the matchVideo does not suffer the color temp emulsion problem but does need to be shot under a single color temp for good color. This is achieved by”

All light sources have the same color temp

Manually white balancing your camera to that source

 

In video if we do not or cannot use the same sources (color temp) then we have to color correct some to match others by using filters on those lights

CTB- correct 3200k to 5,600**

CTO- corrects 6500k to 3200**

CTG – corrects some (greenish) fluorescents to 3,200

 

Color Temp/WB Tip:

If you HAVE to shoot in mixed color temps, then make sure the subject’s face is in the highest temp and WB to that area- the rest will just look warmer and not be as distracting as the reverse.

 

WB Tip:

Always manually WB with the iris set to proper exposure and with the white object in the correct light not shadow.

 

Warming TIP:

Because the white balancing process establishes “white” (using a white card or object in front of the lens to set the balance) under the current light for the camera, we can fool the camera into warming up the picture by using a warm card or Light blue card instead of something white.  These gives us the same results as if we did a normal white balance and then added an 812 or warming filter to the lens of the camera. (Skin tones appear richer) Other colors produce other effects (most not great looking but fun to experiment with) I have found that rather than pay $35. for the card that a piece of foundation sealer foam (comes in a role from the Home Depot) for $3.00 does the job.

 

Bulb Tip:

In the past you needed to Gel correct Tungsten or Florescent lights to Outdoor temp (5,600k) or use an HMI light. Gelling is cumbersome to say the least and often not fully accurate unless using Temp meter and having the correct combination of CT gells. HMIs are very expensive. Today if you can use diffused light that does not need a long throw then looking into the new Compact Spiral Florescent bulbs rated at 5,500k could well be worth your effort. These bulbs come in 3,200 and other temps as well. They are great for softbox or other applications where the light is close to the talent as they do not produce a lot of heat. Check out   www.topbulbs.com

 

*Sunlight alone, Color temp covers a wide range

 Sunrise or sunset 2,000k

One hour after sunrise 3,500k

Early morning/late afternoon 4,300k

Average Noon 5,400k

Mid summer 5,800k

Daylight mix

Over cast 6,000k

Average summer day 6,500k

Light summer shade 7,100k

Average summer shade 8,000k

Partly cloudy 8,000k-10, 000k

Summer/winter skylight 9,500k- 30,000k

 

** Color Temperature Blue (CTB) correction gels are calibrated to raise color temperature to 5500 Kelvin (Daylight).
· They are available in several strengths and are primarily used to correct Tungsten (3200 Kelvin)to Daylight.

 CTB (Full Blue) raises 3200 Kelvin to 5500 Kelvin.
3/4 CTB (Three-Quarter Blue) raises 4700K to 5500K.
1/2 CTB (Half Blue) raises 4100K to 5500K.
1/3 CTB (Third Blue) raises 3800K to 5500K.
1/4 CTB (Quarter Blue) raises 3500K to 5500K.
1/8 CTB (Eighth Blue) raises 3300K to 5500K.

** Color Temperature Orange (CTO) corrects from 6500k

 CTO Full converts Daylight 6500k to Tungsten 3200k

 ¾ CTO converts Daylight 6500k to Tungsten 3600k

 ½ CTO  converts Daylight 6500k to Tungsten 3800k

 ¼ CTO converts Daylight 6500k to Tungsten 4600k

 1/8 CTO Converts Daylight 6500 to Tungsten 5500k

If you have a question or  tip to share, contact Roger at rschut8293@aol.com (and memo it, insights and tips)