Need your help: screenshots from your e-reader

[willus]

Originally Posted by JSWolf

Here are the two screenshots from my Kobo Aura H2O.

Thank you. 1080 x 1386. So indeed, you have little wasted space. Do you know why there is a small black strip at the top of the screen shots? Is that something which can be customized? Can the footers on Kobos be adjusted to whatever size one desires and/or do you have to "hack" them to do so?

[JSWolf]

Originally Posted by willus

Thank you. 1080 x 1386. So indeed, you have little wasted space. Do you know why there is a small black strip at the top of the screen shots? Is that something which can be customized? Can the footers on Kobos be adjusted to whatever size one desires and/or do you have to "hack" them to do so?

It just comes out as black in the screenshot. It's just a small amount of space at the top that's not used. ON the screen, it's just blank with a normal background.

I'll have to ask about it and see if it can be changed.

I've noticed something about the screenshots. The screenshots from the Kobo Readers have more accurate coloring then the Kindles.

[willus]

Originally Posted by JSWolf

I've noticed something about the screenshots. The screenshots from the Kobo Readers have more accurate coloring then the Kindles.

I hadn't intended this as a test of the grayscale conversion algorithm in the devices, but it certainly is interesting. The checkerboard pattern I put in the PDF is full (100%), either red, green, or blue. The Kobos convert the red, green, and blue to 52%, 86%, and 26% of full white, respectively. The Kindle 2 converts to 50%, 33%, and 17%, respectively, and the PW2/Voyage convert to 9%, 35%, and 12%, respectively. Interestingly, none of these match the commonly used grayscale conversion ITU-R BT.709 or BT.601, which are 21%,72%,7% and 30%,59%,11%, respectively, but the Kobos are definitely closest, proportionally, which explains why they look more natural. It is particularly strange to me that all of the Kindles weight the RGB components significantly differently than the ITU-R weightings (K2 has red weighted the highest, and PW2/Voyage have blue weighted more heavily than red). That seems clearly flawed, and would be trivial to correct. How odd.

[KaiReader]

are you only interested in dedicated e-readers? I have a couple of Samsung tablets if you're after those also

[DaleDe]

Originally Posted by willus

I hadn't intended this as a test of the grayscale conversion algorithm in the devices, but it certainly is interesting. The checkerboard pattern I put in the PDF is full (100%), either red, green, or blue. The Kobos convert the red, green, and blue to 52%, 86%, and 26% of full white, respectively. The Kindle 2 converts to 50%, 33%, and 17%, respectively, and the PW2/Voyage convert to 9%, 35%, and 12%, respectively. Interestingly, none of these match the commonly used grayscale conversion ITU-R BT.709 or BT.601, which are 21%,72%,7% and 30%,59%,11%, respectively, but the Kobos are definitely closest, proportionally, which explains why they look more natural. It is particularly strange to me that all of the Kindles weight the RGB components significantly differently than the ITU-R weightings (K2 has red weighted the highest, and PW2/Voyage have blue weighted more heavily than red). That seems clearly flawed, and would be trivial to correct. How odd.

Fascinating information. I will add it to our wiki. Thanks.

[Hampshire Nanny]

These are the screenshots from my K3.


By the way, after attaching my K3 to my PC (Windows 7 Pro) and copying the PDF file to the documents folder on the Kindle, I ejected the Kindle, then unplugged it from the computer. Next, I went to the home screen and waited for it to update with the new PDF file listed. Then I selected it to open. Instead of opening, the Kindle rebooted itself. After the reboot, it took about 4 minutes to list all 380 books on the home page. At which point I selected the PDF file and it opened.

Does anyone know why the first attempt at opening the file might have resulted in a reboot?

Wrong thread -- I've requested that a mod move it. Thanks to the mod for moving this to the right thread.

[willus]

Originally Posted by KaiReader

are you only interested in dedicated e-readers? I have a couple of Samsung tablets if you're after those also

Yeah, I'm mostly interested in e-ink readers. It's not as important to know the precise resolution of tablets which can do rapid pinch-and-zoom.

[willus]

Still hoping for a complete set of Kindle Voyage screen shots.

[j.p.s]

Originally Posted by willus

Still hoping for a complete set of Kindle Voyage screen shots.

I don't know why I have such a hard time making screenshots with the voyage, but I was finally able to capture the first page, attached here.

[DomesticExtremis]

Originally Posted by willus

I hadn't intended this as a test of the grayscale conversion algorithm in the devices, but it certainly is interesting. The checkerboard pattern I put in the PDF is full (100%), either red, green, or blue. The Kobos convert the red, green, and blue to 52%, 86%, and 26% of full white, respectively. The Kindle 2 converts to 50%, 33%, and 17%, respectively, and the PW2/Voyage convert to 9%, 35%, and 12%, respectively. Interestingly, none of these match the commonly used grayscale conversion ITU-R BT.709 or BT.601, which are 21%,72%,7% and 30%,59%,11%, respectively, but the Kobos are definitely closest, proportionally, which explains why they look more natural. It is particularly strange to me that all of the Kindles weight the RGB components significantly differently than the ITU-R weightings (K2 has red weighted the highest, and PW2/Voyage have blue weighted more heavily than red). That seems clearly flawed, and would be trivial to correct. How odd.

Well I've been grappling with something similar and stumbled across this thread.
After doing a lot of reading, I think the problem might be one of different gamma being applied to sRGB output compared with that used by eInk displays.
From WCAG2.0, and it's calculation of relative luminance, the sRGB values are linearized using an (effective) gamma of 2.2 which is the theoretical value for the sRGB colour space.
It seems that eInk is much more like ink on paper - I could not yet find any data for the gamma of an eInk screen, but most printers use a gamma of 1.8 .
I wonder then if instead of trying to find a set of coefficients to use for the weighted average step, it makes more sense to use a lower gamma to linearise the sRGB values in the first place.
If this doesn't make any sense, don't worry - I only barely understand it myself

[kman_!]

Hey, willus! I don't know if you still want screenshots but I have posted mine below just in case. I'm using a PocketBook Basic 2 (600x800, 166dpi. Full specifications: http://www.pocketbook-int.com/us/pro...specifications).

The first 2 screenshots are with the default settings, the last 2 have the information bar hidden by holding the center button on the device.

[SkyBoy]

Hi Willus, many thanks for your efforts.
Attached the Kindle Paperwhite 2015's screenshots for your reference. Thanks.

[willus]

Originally Posted by SkyBoy

Hi Willus, many thanks for your efforts.
Attached the Kindle Paperwhite 2015's screenshots for your reference. Thanks.

Thanks. For your purposes, you can select the Kindle Voyage (-dev kv). It has exactly the same screen shot resolution as the new paperwhite.

[bookp]

I need some help in finding the perfect resolution values for the Sony PRS-T3.
This device, as far as I know, doesn't support screenshots.

I created grid pictures, converted them into PDF, and tested them until I found the resolution with which the grid was displayed perfectly.
It's 738x964 and can be seen in the screenshots and PDF attachment.

As you can see, small black bars show up at the far left and right side of the display. It might be a bug of Sony's software. They appear when the vertical resolution hits 964.

PDFs created by k2pdfopt.exe with 738x964 now look way way better than for example with 768x1024. However, in contrast to the perfect grid, I still see some misalignment every now and then.

On a PC there is no such trouble.

What might be the cause?

[willus]

Originally Posted by bookp

I need some help in finding the perfect resolution values for the Sony PRS-T3.
This device, as far as I know, doesn't support screenshots.

I created grid pictures, converted them into PDF, and tested them until I found the resolution with which the grid was displayed perfectly.
It's 738x964 and can be seen in the screenshots and PDF attachment.

As you can see, small black bars show up at the far left and right side of the display. It might be a bug of Sony's software. They appear when the vertical resolution hits 964.

PDFs created by k2pdfopt.exe with 738x964 now look way way better than for example with 768x1024. However, in contrast to the perfect grid, I still see some misalignment every now and then.

On a PC there is no such trouble.

What might be the cause?

I had issues with my kindle2 trying to stretch/scale the PDF bitmap if it had extra white space, thus destroying the 1-to-1 pixel mapping from the PDF bitmap to the e-reader display. That is why there are -pad (-p) and -mc options. -mc will mark the corners of the page with a single dark pixel to prevent auto-scaling on the e-reader, and -pad will add some extra padding around the page, which I also needed to preserve the 1-to-1 mapping on my kindle. You might experiment with these on your PRS-T3.

The black bars you are seeing almost look like a display imperfection/anomaly. E.g.. the one on the top clearly looks like it is only visible on the far right and then gradually disappears into the edge of the display.