Stupid iPhone photography app
A lot of iPhone apps of questionable merit are targeted towards photographers. The most stupid I've seen so far is a supposed white balance tool called iGrayCards. Here's a quote from the description of the app:
“Simply by including the running App in the frame to be photographed, it can be referenced in most modern image processing software to set the White Balance point for the whole image.”
Whoever created this app is absolutely clueless about how a white balance cards (e.g. WhiBal and similar tools) used by photographers works.
The whole idea with a white balance card is that the camera is used to record the colour temperature of the light hitting the scene (e.g. sun, open shade, incandescent, flash, whatever). The card is simply a spectrally neutral surface that reflects the incoming light without adding any tint of its own.
If you take a picture of your iPhone running this app, you only record the colour temperature of your iPhone's back-lit LCD. The screen of your iPhone set to “18 % gray” will of course yield same colour temperature at all times, and not be able to tell you whether scene is lit by incandescent lights or by the sun.