Upload & Sell: Off
At long last, I own a color temperature meter. Something I always wanted.
I was taking some test readings of gels on my SB-24's when I noticed one was 300k warmer than the others. It was the only one with a diffusion cup on it, an ebay generic. Always assuming those are 100% neutral, my first thought was that this one flash had an aging bulb. I took the diffuser off anyway and the reading became the same as the other units. It was the diffuser that shifted the color by 300k.
Next, I tested my SB-600 with a Sto-Fen diffuser. The color shift with the diffuser was 550k! My SB-800 with the factory diffuser had the least amount of shift: 250k.
To complete the picture I should add that the SB-24 diffuser is one year old, the Sto-Fen is five years old and the SB-800 diffuser is three years old -- same as the flash.
I always knew modifiers like umbrellas and softboxes effected the color temperature, but never suspected these little hard plastic cups. With three brands tested, I think +300k is a good estimate, worse as they age.