Can anyone tell me why e-ink displays need to 'flash' between pages?

It's as though it has to clear the screen then redraw it in front of you.

Occasionally in videos on YouTube I see what can only be described as a double update (ie a definite page change then a redraw of the same page).

It's as though the frame buffer for the screen is the screen itself rather than another area of memory.

Students learn that flickering in computer animation occurs because you momentarily see a blank screen before the next frame is redrawn. A technique known as double buffering alleviates this by doing the clearing and redrawing 'off screen' then block transferring the new frame in a single pass

Is there something inherent in the design which prevents this for e-ink?

Is there some way to do a 'delta' update of the screen? i.e. Most of the page in an e-book will remain white between pages. Surely it would be more battery friendly (I understand that, like CMOS, e-ink only draws power during a change) and easier on the eye to only change the pixels which differ between the pages......

I've seen basic animation performed on an e-ink screen showing that some kind of delta updating mechanism should be possible: http://www.youtube.com/watch?v=3n2xxqMQyfY

or even the October 2008 Issue of Esquire magazine which contained an e-ink section on the front cover has a non flickering (actually more of a fading effect) animation
http://www.youtube.com/watch?v=9EWb1zHIx38

The impression I get (again from YouTube) is that the Edge page change is slightly quicker than say a Kindle DX (is this true?) but I'm sure there must be a way to prevent the annoying black page screen update when changing pages.

BTW I managed to win a White Entourage Edge on Ebay ! So I'm looking forward to perhaps having secured one of the quickest delivered and cheapest Edges in the UK ! I'm am so lloking forward to getting it especially with the recent software update that everyone is raving about !

In short I love the camaraderie which shines throughout this forum, which will make the Edge the success it deserves to be.


P.S. You can be as technical as you like in the replies - I have a science based Ph.D. so no need to be gentle with me