Ideal image size?

doubleshuffle · 07-05-2015, 06:07 AM

What do you consider a perfect size for images in an e-book?

In the project I'm working on right now, I have very good scans in high resolution (about 1700 x 2600 px for a whole page illustration). Obviously, those images must be scaled down, but how far?

My Aura HD has a 1080 x 1440 px screen, and I think the H2O and the new 6-inch hi-res screens are very similar. So is this the image size I should go for, or would you recommend a smaller size to keep the file size down?

Has anyone ever thought of publishing different versions, low-res e-ink, hi-res e-ink, tablet?

rubeus · 07-05-2015, 06:44 AM

If these images are displayed on a single page just let them in their original size and let the reader scale them down by wripping them into svg.

Jellby · 07-05-2015, 08:17 AM

There's no need to scale them down. There's only a trade-off between quality (in present or future readers) and filesize. Whatever might be "ideal" now may be poor in a couple of years, and the "minimum acceptable" depends of the nature of the image (for example, if it's a map, it must be readable).

That said, I suggest 900×1200 should be good enough and large enough for most images, and not too heavy for e-ink readers. Even if your source scan has higher resolution, it might benefit from downscaling to remove paper texture or offset patterns, but if it's already "perfect", you can leave it like that.

Turtle91 · 07-05-2015, 09:11 AM

Ditto

Maps that blur out when I'm zooming in are really annoying - so definitely make them large enough. And a 700Mb cover that is 400x600 is probably a little overboard and can be scaled down. I typically look for around 200 Mb or less for a 1600px tall image in 24bit color.

doubleshuffle · 07-05-2015, 01:08 PM

Thanks for the input.

Of course there is no absolute need to scale down the images, but I was thinking that it won't make much sense to have larger files than current readers can display.

No maps in this project, but I've also come across maps that made no sense due to unreadability, so with those I would always tend to err on the side of higher-than-necessary resolution.

I think I agree with 900x1200 or perhaps a little larger; I'll see what the final file size will be. Of course I do all the cleaning up before downscaling and will keep the hi-res files, so it will be easy to come up with an improved version when the current resolution becomes inadequate in a few years.

07-05-2015, 06:07 AM	#1
doubleshuffle Unicycle Daredevil Posts: 13,944 Karma: 185432100 Join Date: Jan 2011 Location: Planet of the Pudding Brains Device: Aura HD (R.I.P. After six years the USB socket died.) tolino shine 3	Ideal image size? What do you consider a perfect size for images in an e-book? In the project I'm working on right now, I have very good scans in high resolution (about 1700 x 2600 px for a whole page illustration). Obviously, those images must be scaled down, but how far? My Aura HD has a 1080 x 1440 px screen, and I think the H2O and the new 6-inch hi-res screens are very similar. So is this the image size I should go for, or would you recommend a smaller size to keep the file size down? Has anyone ever thought of publishing different versions, low-res e-ink, hi-res e-ink, tablet?

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07-05-2015, 06:44 AM	#2
rubeus Banned Posts: 272 Karma: 1224588 Join Date: Sep 2014 Device: Sony PRS 650	If these images are displayed on a single page just let them in their original size and let the reader scale them down by wripping them into svg.

07-05-2015, 08:17 AM	#3
Jellby frumious Bandersnatch Posts: 7,548 Karma: 19500001 Join Date: Jan 2008 Location: Spaniard in Sweden Device: Cybook Orizon, Kobo Aura	There's no need to scale them down. There's only a trade-off between quality (in present or future readers) and filesize. Whatever might be "ideal" now may be poor in a couple of years, and the "minimum acceptable" depends of the nature of the image (for example, if it's a map, it must be readable). That said, I suggest 900×1200 should be good enough and large enough for most images, and not too heavy for e-ink readers. Even if your source scan has higher resolution, it might benefit from downscaling to remove paper texture or offset patterns, but if it's already "perfect", you can leave it like that.

07-05-2015, 09:11 AM	#4
Turtle91 A Hairy Wizard Posts: 3,347 Karma: 20171571 Join Date: Dec 2012 Location: Charleston, SC today Device: iPhone 15/11/X/6/iPad 1,2,Air & Air Pro/Surface Pro/Kindle PW & Fire	Ditto Maps that blur out when I'm zooming in are really annoying - so definitely make them large enough. And a 700Mb cover that is 400x600 is probably a little overboard and can be scaled down. I typically look for around 200 Mb or less for a 1600px tall image in 24bit color.

07-05-2015, 01:08 PM	#5
doubleshuffle Unicycle Daredevil Posts: 13,944 Karma: 185432100 Join Date: Jan 2011 Location: Planet of the Pudding Brains Device: Aura HD (R.I.P. After six years the USB socket died.) tolino shine 3	Thanks for the input. Of course there is no absolute need to scale down the images, but I was thinking that it won't make much sense to have larger files than current readers can display. No maps in this project, but I've also come across maps that made no sense due to unreadability, so with those I would always tend to err on the side of higher-than-necessary resolution. I think I agree with 900x1200 or perhaps a little larger; I'll see what the final file size will be. Of course I do all the cleaning up before downscaling and will keep the hi-res files, so it will be easy to come up with an improved version when the current resolution becomes inadequate in a few years.

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