CRI vs TLCI vs TM-30 vs SSI Explained with the Sekonic C-800

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The Sekonic C-800 is able to measure CRI, TLCI, TLMF, TM-30 and SSI. All these indexes have been designed to give you confidence in the color rendering of the lights that you are using. This video will discuss what each of these indexes mean, and how you can use the C-800 to evaluate and measure them.

Reference Links:

Tech3355 document released by the EBU
https://tech.ebu.ch/docs/tech/tech3355.pdf

Protocol Fall 2015 TM30 - By Mike Wood
https://www.mikewoodconsulting.com/articles/Protocol%20Fall%202013%20-%20TLCI.pdf

Understanding & Applying ™-30-15 - By Michael Royer & Kenin Houser
https://www.energy.gov/sites/prod/files/2015/09/f26/tm30-intro-webinar_9-15-15.pdf

More About SSI
https://www.oscars.org/sites/oscars/files/ssi_overview_2019-03-04.pdf
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The Sekonic C-800 is able to measure CRI, TLCI, TLMF, TM-30 and SSI. All these indexes have been designed to give you confidence in the color rendering of the lights that you are using. This video will discuss what each of these indexes mean, and how you can use the C-800 to evaluate and measure them.
We will help you choose which one of these indexes, or a combination of indexes that you may want to provide increased confidence in the lighting you use for your next production, and how to evaluate the information the C-800 gives you.
Before getting into these indexes there are a few things we would like you to understand.
First, we want you to understand the observer. The observer is what each of these indexes uses in order to measure the quality of their score. For example CRI and TM-30 will use human vision as the observer. TLCI will use a 3 chip broadcast camera as the observer, and SSI removes the bias of the observer all together.
Second, we want to explain what problem each of these indexes was designed to solve for… and how you can interpret its information to help out with your next production. CRI, Color Rendering Index, is based upon the evaluation of 15 colors, using the human eye as the observer.
The first 8 colors are what the Ra or CRI score is based on, and R9 through 15 are additional colors that allow you to further evaluate the quality of a light source.
You may hear of CRI extended, which is a score given based upon the evaluation of all 15 colors, but it is not the standard that lighting manufacturers are using when scoring their lights.
CRI was designed to score a light based upon how the human eye would be able to accurately perceive colors under ideal daylight conditions.
It allows us to examine how light sources that attempt to reconstitute daylight such as Mercury Vapor, Fluorescent, Incandescent and LED will perform. But originally it was designed to judge fluorescent lamps.
OK, so how can you use the C-800 CRI readout to evaluate the lights you intend to use.
Please note that this next section is bias toward what a filmmaker may look for when evaluating a light.
CRI is measured from 0-100. A Ra value between 85 - 95 is seen as good, and above 95 as exceptional. For image makers this doesn't mean a light is going to be good or bad. It simply a score based upon 8 very muted colors. In today's manufacturing process of LED’s, a lighting manufacturer can tweak “game” their lights to score high, but it may still not give you skin tones similar to standard tungsten or standard daylight.
Most gaffers and DP’s that trust CRI look at R9 Strong Red, R13 Light Yellowish Pink, and R15 Asian Skin Tone, to see how well a light is going to render skin. If a light has a high CRI (Ra) value and R9, R13 and R15 values above 85 most predict that it will give you pleasing skin tones. If R10 yellow, R11 green, R12 blue and R14 Moderate Olive Green (leaf) score high as well. You most likely have a light that won’t suffer from severe color rendering problems.

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