10-13-2019, 09:29 PM | #1 |
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How many shades of grayscale does the Forma have?
How many shades of black/grayscale does the Forma have?
White = is one color Black = another color How many levels of gray are there in between completely black and completely white? I need this info to figure out, when I convert full-color comic books or images (for the purpose of saving space on my forma), what number to use in the blank for "maximum colors". Thanks! |
10-13-2019, 09:37 PM | #2 |
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Can't say for the Forma, but experiments I did a long time ago on a Kobo Mini indicated that 16 levels of grey could be displayed though not necessarily discerned by the eye.
There is a fairly narrow contrast range on e-Ink screens, though it will improve with a frontlight. |
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10-13-2019, 09:49 PM | #3 |
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DomesticExtremis, thanks for your quick reply.
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10-13-2019, 10:19 PM | #4 |
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16 shades of gray, with an even stride of 0x11 (i.e., 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF), like every B&W eInk screen since the Pearl days.
Last edited by NiLuJe; 10-13-2019 at 10:22 PM. |
10-14-2019, 11:38 AM | #5 |
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One thing I'll add, the Kobo Forma, (and indeed, every model of Kobo over the past 5 years, excluding the Aura One.) does a *really* good job of dithering with cbz files. I would not bother downscaling the colour at all, or at most, reduce to greyscale to reduce file size.
I exclude the Aura One because, for some reason, even though they all have the same firmware, I can clearly see the dithering pattern with the naked eye on that one. Not sure if I could get better results with by downscaling the colours myself, but it still looks great for most B&W Content. Last edited by rashkae; 10-14-2019 at 11:46 AM. |
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10-14-2019, 02:22 PM | #6 |
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@rashkae: That's because the Forma (and other Mk. 7 devices) support hardware dithering, and it's indeed pretty decent (still slightly more obvious than a good 8x8 matrix (or a good error diffusion algo), but, pretty decent, and essentially free, which pretty much trumps any other concerns given how serviceable it is). Nickel's own isn't half-bad, but is hobbled by various legacy reasons, a visible consequence of that being a more obvious pattern.
Last edited by NiLuJe; 10-14-2019 at 02:26 PM. |
10-14-2019, 03:08 PM | #7 | |
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Quote:
Last edited by rashkae; 10-14-2019 at 03:20 PM. |
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10-14-2019, 04:30 PM | #8 |
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@rashkae: I was going to say that one can play with the hardware dithering settings and/or input to make the pattern more obvious, and in particular thanks to how processing is highly vectorized, that can translate in visible, wide vertical stripes .
(You may be talking about much narrower vertical "stripy" patterns, though, and that would just be the pattern induced by the matrix). If you have a Mk. 7 on hand, you can switch between HW & SW dithering in KOReader. Except we're using the kickass matrix ported from ImageMagick, so it kinda rocks . ---- Also keep in mind that dithering patterns have an extremely adverse effect on eInk ghosting, in that they basically feed each-other in a loop, so you may want to take that into account when making comparisons (i.e., start from a flash to white). Last edited by NiLuJe; 10-14-2019 at 04:38 PM. |
10-14-2019, 04:32 PM | #9 |
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Kobo's software dithering is better then Amazon's.
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10-14-2019, 09:43 PM | #10 |
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Hilariously untrue (especially for your beloved epubs) but at least it doesn't look horrible anymore, and the large forma screen more than makes up for it
Last edited by rashkae; 10-14-2019 at 09:47 PM. |
10-14-2019, 09:45 PM | #11 | |
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The matrix is only visible to me, without artificial magnification, on the H20 2nd edition.. But I have to *really* try. Last edited by rashkae; 10-14-2019 at 10:00 PM. |
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10-15-2019, 12:31 AM | #12 |
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Yeah, for devices with no HW dithering, you can take a screenshot and look at it on an LCD screen, that'll preserve Nickel's funky pattern, and it'll likely be much more obvious there than on eInk.
(And by "screenshot", I mean ideally an fbgrab, because Nickel's screenshot feature used to do extra funky stuff on some devices. This *may* no longer be the case, though, because why would I bother with that clunky feature when I can play with fbgrab over CLI? ;p [meaning I haven't tried it in over two years]). But HW dithering doesn't affect the fb content, so, you'll only be able to eyeball it the old fashioned way . Last edited by NiLuJe; 10-15-2019 at 12:34 AM. |
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