TM-30 is an IES method for evaluating the colour rendition of a light source. It uses 99 colour evaluation samples and reports several results, including the fidelity index Rf, gamut index Rg and graphics showing shifts across hue groups.
Rf and Rg
Rf describes average similarity to a reference, on a scale reaching 100. Rg describes average change in chroma: 100 corresponds to the reference gamut area, values above 100 indicate an average increase, and values below 100 an average decrease. A high Rg is not a higher fidelity score.
Read beyond the two numbers
Averages can hide differences between colour regions. The colour-vector graphic and hue-specific results help show whether a light changes reds differently from blues or greens. Record the TM-30 version and the fixture’s CCT and operating mode when comparing reports.
Practical example
For a product shoot, two fixtures with similar Rf can still render a saturated package differently. Use the report to identify areas worth testing, then shoot the actual product with the chosen camera and grade. TM-30 describes human-vision colour rendition; it does not model a particular camera sensor.
Equipment examples
The Aputure LS 600x Pro entry includes the manufacturer’s TM-30 figures alongside its other colour-rendering specifications.
Related terms
CRI (Colour Rendering Index) · TLCI (Television Lighting Consistency Index) · SSI (Spectral Similarity Index) · CCT (Correlated Colour Temperature)
References
IES: colour fidelity and TM-30 · IES: gamut index Rg · US Department of Energy: understanding TM-30