Not All Light Can Be White Balanced

Did you know that not all light can be white balanced?

Just because you can see light, doesn’t mean that it has all of the colors necessary to reflect all colors.

When you look at a rainbow, you see the full spectrum of light – Roy G. Biv, as my dad taught me – Red, Orange, Yellow, Green, Blue, Indigo and Violet.  That’s because the sun is full-spectrum light.

I remember as a kid of about 10 years old having a dark blue jacket.  My little brother had the same color jacket.  It was night, and he was standing under a parking lot light.  His jacket no longer looked navy blue.  It looked an ugly color of green.  I looked at mine too.  It too looked green.   I pointed this out to him, and we soon noticed that when car headlamps lit our jackets, they looked blue again.  This was the first time I experienced partial spectrum light.

Take a look at this graph…

http://micro.magnet.fsu.edu/primer/lightandcolor/images/lightsourcesfigure3.jpg

On the graph you’ll see the mercury vapor lamps peak in the green and yellow colors,and some in the violet.  This would explain the ugly coloration of my brother’s and my jackets. 

Now, let’s apply this to photography…

If you are using a light source that is deficient in a portion of the spectrum, no amount of white balancing can bring you around to a balanced color in your image.  The laws of physics are in play.  You cannot break a law of physics.

It’s like this… supposed you had a board that bounced back ping pong balls thrown at it.  You have red, blue and green ping pong balls (red, blue and green are the colors of the pixels in your digital image).  Now, if you threw all your red blue and green ping pong balls at the board, and they all bounced back, that would be analogous to full spectrum light hitting a white object.

Now, suppose you only through red ping pong balls at the board.  Would you get any green and blue back?

Of course not.  It would be impossible.  Thus it is with light.  What you thrown on your subject will greatly affect what you get reflecting off your subject.

When you purchase lights for indoor photography, keep this in mind.  Not all lightbulbs are created equal.   For example, here’s a graph that compares tungsten with fluorescent light…

http://micro.magnet.fsu.edu/optics/lightandcolor/images/lightsourcesfigure2.jpg

Many light manufacturers publish the spectrum for their lights.  You can contact them if you desire to find out the performance of their products.    That said, there is a reason makes of photographic lights use certain types of lights – color spectrum.  It is all about getting a full spectrum of light to throw at your subject.

One final note…

Experimentation always leads to innovation.  Don’t be afriad to experiment.  For example, take a red LED, light a scene with it, and then see what happens when you try to bring it into white balance.  Who knows what colors you might end up with as the computer tries to bring the red spectrum into compliance.

~ by beckwithmansion on October 6, 2009.