PRS-650 Why does the refresh rate change?

[blu-]

When I change pages, sometimes it's fast and sometimes it's slow. When it's slow, it looks like the page is refreshing rapidly a few times before it changes. When it's fast it just looks seamless.

When I turn on the device it changes slowly. Then after a dozen or several dozen pages it turns faster.

[delphin]

e-ink displays are actually a kind of nano-technology where microscopic e-ink pigment particles get yanked around in a semi-fluid medium.

So e-ink displays are dealing with physical movements on a microscopic level, not just moving electrons around at nearly the speed of light.

The response of the e-ink pigments is effected by temperature, so the electronic driver circuits have to compensate by slowing down the screen changes when it's cooler, in order to allow the pigment capsules time to fully respond.

As you hold the reader in your hand, it warms up and the response time improves.

Sometimes when the temperature changes quickly, it can't adjust quickly enough, and the pigments do NOT have time to respond fully during a screen change, then you get 'ghosting'.

So slight changes in update speed, and occasional slight ghosting, are normal, and not something that you should be overly concerned about unless you compare your reader side by side with someone else's and find that yours is noticeably worse.

[amujee]

That was a very easy-to-understand explanation of e-ink technology. Thank you delphin.

[Penforhire]

I've noticed page turn variations that, I believe, are unrelated to temperature. It doesn't bother me but it may be a function of the e-book file structure and how it buffers or queues up for screen display.

[ardeegee]

Originally Posted by blu-

When it's slow, it looks like the page is refreshing rapidly a few times before it changes.

With this, you are probably seeing the difference between 2 "color" mode pages (plain text) and 16 "color" mode pages (illustrations, photos, etc.) which refresh in more than one step in quick succession.

[delphin]

Originally Posted by ardeegee

With this, you are probably seeing the difference between 2 "color" mode pages (plain text) and 16 "color" mode pages (illustrations, photos, etc.) which refresh in more than one step in quick succession.

This is an excellent point. I think the reader is always in at least 4 color mode, so that it can anti-alias the fonts, but 16 level gray scale photographs and illustrations do require special handling.

Again, due to the micro-mechanical details of e-ink, to get the fine gradation of 16 shades, while avoiding ghosting, they use a more complex page refresh sequence.

The reader is smart enough to sense whether the next up-coming page is simple 2 color text only black and white or whether it has something like an illustration or photograph, and picks the refresh sequence that it needs automatically.