here is repost of my reply in the Kindle thread https://www.mobileread.com/forums/sho...26#post1776926
Interesting article, I don't have the K3 but since they also mentioned Nook STR(which I still have atm), I assume the K3 & Nook have the same screen.
I did some brief test just now by loading a pure black & pure white(blank) page on to each reader, then used my X-Rite i1 spectrophotometer to measure each of its black & white color data, I don't find the black "a little darker" on the Nook STR, in fact, the K4's black is darker.
Below are the comparison image I've created using photoshop based on the L*a*b reading of the spectrophotometer, then converted to sRGB color space:
If it says anything, as you can see(if your monitor can differentiate the differences) that the black on the Kindle NT is actually darker. And the contrast on the K4 between the darkest and whitest is actually slightly greater than the Nook STR is capable off( 48.8 vs 46.8 for Delta E CIE2000 & 52.5 vs 49.7 for Luminosity).
The Delta E CIE2000 for the pure black between the two devices is 1.6.
The Delta E CIE2000 for the pure white(blank) between the two devices is 1.0.
To put the above differences in context for people who're not familiar with those readings, the smallest difference human eyes can detect is 1.0.
So with all other variables included such as manufacture unit to unit tolerance, instrument & display supply variance, the screen between the two are pretty much the same in terms of hardware black & white display capability.
p.s. With no disrespect to Tom's hardware, where there're full of experts smarter than me, IMHO using a microscope to take a picture of the screen is not the most accurate way to evaluate the shadow/light differences, a spectrophotometer is much more reliable.