Visually measuring CRI

[Garth Herrick]

Hey Holly,

Thanks for the tip! I ordered my diffusion grid sheets from EdmundOptics.com a couple of days ago and bingo, they had already arrived yesterday! A lot of packaging for a little sheet. The cost was $19.27 with shipping.

Anyway, I have had some interesting revelations as to the shortcomings of my studio lighting. I can't believe how fluorescent lights are composed of just a few simple steps on the spectrum scale. It is no wonder that so many colors can look so dead. The so-called full-spectrum incandescent bulbs seem to completely lack the production of anything in the yellow range (as do the fluorecents). My 500 watt photographic halogen lamp has a full spectrum 100 CRI, but it is 3200 K, rather than daylight. I wonder how the so-called 98 CRI full spectrum fluorescent tubes look?

Looking at a television or computer monitor, it is obvious there are only three phosphers, i.e.: RGB.

Thanks again, whenever I look at new lighting, I take one of these sheets along for a quick analysis.

Garth

[Holly Snyder]

Garth,

Thanks for posting your results with the diffraction grating sheets, they're interesting. I'm hoping to purchase the Lumichrome 5000K, 96 CRI fluorescents pretty soon, I'm curious to see their spectrum too.

You can also take two pieces of cardboard, hole punch one, then tape them together (with the hole now in the center). No light should get through the tape joint (black duct tape works great), and preferably the cardboard would be black on one side. Hold this between your light source and the grating, with the black side facing you. On the grating you'll see a smaller, but easier to look at spectrum, with a nice black background to set it off. You'll probably have to move the grating up and down and front and back, until you find where the spectrum image appears.

I'm glad this was useful to you.

Cheers,

Holly