First, there's the issue of the font size. The text on screen was displayed at 12 and 18 point, while the printed material was described as being articles printed from the NYTimes website or books, both of which are printed at about half (8 - 10 pt font size). Gee, I wonder if a larger font size could make the text easier to read?
And then there is the issue of the fonts used in the study. The book and NYTimes printout were likely printed in Times New Roman or some other serif fonts, while the Kindle and iPad likely displayed the text in a sans-serif font. As you can see from the image at right the 2 types of fonts don't look the same.
There has been an ongoing debate over whether one type of font was easier to read than the other (Wikipedia). I'm not going to get into the arguments now, but I would suggest that in this case the sans-serif font may have been easier for the test subjects with impaired vision to read because the characters are simpler and easier to recognize.
So all in all, I'm not sure how much this study is really worth.
I suppose it is rather funny for a blogger obsessed with digital reading to dispute the value of reading on a tablet, but then again I never needed convincing. I have always increased the font size to make reading easier, so the alternate explanation for the improvements shown in this study was fairly obvious to me.
via WebMD <- worth reading because they included technical details not found elsewhere
image by Iain Farrell