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That only shows differences in white balance and tone. It can't give you any information about the CRI since you only have 3 channels of colour sensors in your
by janekm 7y ago
That only shows differences in white balance and tone. It can't give you any information about the CRI since you only have 3 channels of colour sensors in your camera.
If you use a colour swatch palette that would be different.
- _ph_ 7y agoYes, of course. It doesn't give you a "spectrum" at all. Only a very rough guesstimate on how the colors are balanced. But good enough to see, whether there is a large blue peak (blue line much stronger than red and green) or not. Just using your camera and a rgb histogram. But using a color palette is a great idea. With some calibration work, this could give a rough spectral curve with a single picture. I need to investigate this :). One would require to get a palette, where the colors are generated not by rgb pigment mixing but by absorbing/reflecting distinct wavelengths. Of course, the MacBeth color targets would fufil that condition, now how to get a wavelength calibration from this? Have to read up on things...
- janekm 7y agoAnother option would be to use colour correction gels like from Rosco. They publish transmission curves for their gels: https://emea.rosco.com/en/products/filters/r3220-double-blue-ctb https://emea.rosco.com/en/products/filters/r3220-double-blue... (click on the little i). You could take pictures of the light source through a set of different gels and reverse to an approximation of the spectrum of the light source. Interestingly they are also now offering gels to correct the colour casts of LED lighting: https://emea.rosco.com/en/product/opti-flecs https://emea.rosco.com/en/product/opti-flecs There are samples swatches of their gels, which can be had by either asking a theatrical lighting supply company or on eBay.