In our initial test we looked at the same blocks of text using an iPad against my current e-Reader, the SONY PRS-700, which is a 8-grey scale Vizplex screen of the previous generation. My living room only had natural lighting coming in from the sides of our bay window. This is iBooks shown at approximately 50 percent brightness level. I found that anywhere between 20 and 50 percent was about as high as you want to go in daytime ambient natural light. While not evident in this picture, the Vizplex screen is very easy to read in ambient natural light indoors.
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