pb InkPad color 3 resolution

[ibat]

On the PB website they say in the specs of InkPad color 3:
DPI 300, 150 (color)

what does this mean?

* the InkPad color 3 has 300 DPI in black and white and 150 in color mode? How is that on pages that are partially in color?

* or does it mean the E-Ink Carta background is in 300 DPI has a 150 RGB raster in front resulting in 150 DPI whatever?

[dmalinovsky]

This is related to the way E-ink Kaleido 3 screen works: https://www.eink.com/brand/detail/Kaleido3

If the page is partially in color, any color content will be displayed in 150 PPI and B&W content in 300 PPI. If you have a colored background and B&W text on it, the text should be in 300 DPI as well, but I didn't have a chance to actually test it, so don't quote me on that.

[Quoth]

Originally Posted by dmalinovsky

This is related to the way E-ink Kaleido 3 screen works: https://www.eink.com/brand/detail/Kaleido3

If the page is partially in color, any color content will be displayed in 150 PPI and B&W content in 300 PPI. If you have a colored background and B&W text on it, the text should be in 300 DPI as well, but I didn't have a chance to actually test it, so don't quote me on that.

Physics. It uses a 300 dpi screen. The colour is 150 dpi at best. You can't ever have true B&W 300 dpi, that's gone because of the filter, which is passive. Mono will look better than 150 dpi and certain mono content will be closer to 300 dpi appearance.

Marketing hyperbole that would be quickly squashed if a TV or laptop maker tried claiming the native LCD panel resolution is the mono resolution.

[ibat]

Originally Posted by Quoth

Physics. It uses a 300 dpi screen. The colour is 150 dpi at best. You can't ever have true B&W 300 dpi, that's gone because of the filter, which is passive. Mono will look better than 150 dpi and certain mono content will be closer to 300 dpi appearance. ...

Or possibly even worse?

• If the back panel is only 300 DPI would that not imply that each color could maximally have 100 DPI? ( 100 x 3 =300) This would leave us no space for the grayscale.
• Or if we reserved 150 DPI for grayscale this would leave us only 50 DPI for each color pixel ( 150 + 3 x 50 =300).

Does this make sense?

[JSWolf]

The problem is that the color filter makes B&W much more dark.

[chrisridd]

As a slight aside, I recall that when broadcast TV went from mono to colour the extra colour signal was effectively at a lower resolution than the core grayscale signal.

Anyway, back to eink :-)

[Quoth]

Colour TV (and most digital video) is still less than mono resolution. For analogue about 1/4 horizontal and on some systems 1/2 vertical. VHS is about 1/6th to 1/8th horizontal colour resolution. The mono resolution was unaffected. With digital there is less data used for the colouring information than the monochrome image. See https://en.wikipedia.org/wiki/Chroma_subsampling#4:2:2

But colour LCD and colour eink work differently for lighting. The mono display panel (either LCD or eink) has a coloured filter, so the mono resolution is also lowered. An LCD or eink 1920 x 1080 coloured panel is using either 5760 x 1080 mono cells or 3840 x 2160 mono cells, depending on if it's stripes or a 2 x 2 pattern. There are other filters.
LCD is back lit so the light is attenuated once by the the filter, and the light is simply made brighter. The eink is front lit so the filter reduces the brightness of the daylight or the front light twice.

So colour eink is inherently darker and lower resolution than the equivalent mono panel with no filter. They changed from more saturated colours (Triton) to pastel shades (Kaleido) to brighten it a little, on the basis that there are so few grey levels (14 + black + white) that the colour is rubbish anyway compared to LCD, CRT, OLED or QLED (actually LCD with a blue backlight and only "quantum" dots for green and red, that change the blue instead of filter "white" light).

[Quoth]

Originally Posted by ibat

Or possibly even worse?

• If the back panel is only 300 DPI would that not imply that each color could maximally have 100 DPI? ( 100 x 3 =300) This would leave us no space for the grayscale.
• Or if we reserved 150 DPI for grayscale this would leave us only 50 DPI for each color pixel ( 150 + 3 x 50 =300).

Does this make sense?

Stripes would be 100 dpi x 300 dpi. Older Triton eink. Also Sony Trinitron CRT and common on LCD.
But the Kaleido eink (and newer LCDs) uses a 2 x 2 pattern, hence 150 x 150 dpi. Harder to make and align.