Luxi For All
Luxi For All is a small attachment for iPhone, iPad, and iPod Touch which works with a FREE app to turn your device into an incident light & color meter (color metering requires a third-party app). When paired with the FREE Luxi™ app, Luxi For All will help you determine the best settings for your DSLR or other camera, so you can take perfectly exposed and color-balanced photos and videos.
"Over the past 50 years, I have been a professional photographer and then a professional videographer. All I can say is the Luxi fulfills my needs. It is worth every penny, and I thank you." - Richard W.