If you want to view the color spectrum of a light source in your studio, there’s actually a super cheap and easy way to do so: an ordinary CD or DVD can do the trick. Simply allow the light to reflect from the surface of the disc into your eye — it acts as a diffraction grating, allowing you to see the different color bands in the light.
Here’s an 8-minute video in which Matthias Wandel demonstrates the technique using different lights in his woodworking shop:
Using this trick, you can see how different types of lights emit wavelengths differently. Here’s a still frame from a comparison Wandel does between a CFL bulb (left) next to an LED bulb (right):
As you can see, the CFL emits very specific wavelengths of light, whereas the LED bulb is very smooth in comparison. While these lights may look similar to the naked eye, the spectrum differences can make a difference in photos. For example, objects will look completely different in black and white photos depending on which kind of light you use (Wandel demonstrates this in the video above).
If you have a CD lying around, try using it to examine the quality of the lights you’re using for your shoots.
Thanks for sending in the tip, Julian!
Image credits: Header CD photo by Luis Fernández García, and video and still frame by Matthias Wandel