Quote:
Originally Posted by EternalCyclist
shows a pattern with 16 levels of grey.
After overwriting the framebuffer with a value 255 for the first 100 lines I have the impression that the bar is brighter than the brightes square drawn by eips.
To overwrite the first, e.g. brightes square, with this ultra-white (255), one first has to overwrite it with a different value. Otherwise it won't update.
Crosschecking:
Filling the screen with bars of value alternating from 240 and 255 shows difference shades. (I assumed, that the upper 4 bit determine the grey level).
So, I have actually 17 levels of grey and I have to set background to 255 to get maximum contrast?
The background the home screen is actually as bright as the 255-bar.
Strange: Filling the screen with 0x10 and 0x00 bars, shows no difference. So using 0x10 to 0xf0 plus 0xff gives me again only 16 levels. But I see 17 different levels when overwriting the eips pattern. |
That is just a visual artifact of two properties of the screen:
*) The e-ink particles are much smaller than the resolution. I.E: There are many particles per pixel.
*) The e-ink particles are not independent. They interact with each other (within the area of a single pixel).
Switch the group of particles within a single pixel from one maximum value to the other maximum value, and. . .
The ones that are already at the target value do not have to move,
The ones that are not at the target value have to move,
Since they interact, not all of those move the same amount.
But if you repeat the max-to-max switch often enough, you can get nearly all of them into the same position.
Giving an overall appearance of a denser color (white or black).
If an analogy is clearer, think of materials behavior to being magnetized.
The first stroke of the magnetic field over the material only aligns a some of the magnetic domains of the material.
Repeated stroking of the magnetic field aligns a larger percentage of the magnetic domains with each stroke.
If you could see the effect of the magnetic domain alignment, you would see the same "ghosting" effect that the e-ink particles have in their electrical field alignment.
Translation:
It is not a 17th gray scale level, it is a better approximation of the 16th gray scale level.