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Old 06-08-2014, 05:29 PM   #1
eggheadbooks1
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For the longest time we've all had to keep our images in ePubs below the 300KB limit, with 260KB the norm to account for differences in the way ereaders read image size. I am told this was never a limitation of the ePub format itself but originated from the way Adobe programmed ADE, and older devices based on ADE (like Sony) would crash if images exceeded 300KB. But with the advance of high-resolution tablets, and high-resolution ePub devices such as Kobo's Aura, Ark, etc., why are we STILL restricted to this ridiculous 260KB image size?

I realize there are old devices still out there that will crash, but at some point we have to move on if we are to produce books for the newer higher-resolution devices. To not do so would be like not producing HD DVDs because some people can't watch them on their old TVs. Perhaps we may find ourselves having to produce two products, a smaller-image ePub for older devices and larger-image ones for newer devices, distributed under different ISBNs and even titles (like adding "HD" to the title).

Anyone heard anything about this on the wind?

Last edited by Jellby; 06-09-2014 at 03:21 AM.
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Old 06-08-2014, 06:22 PM   #2
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At what point do we deprecate the 300KB image limit?

You are not restricted, it is simply stupid to create an ebook that you intend to be read on all devices, if some of them will crash on it.

Do some people still have those devices? (yes) Do you want your books to be able to be read on them? (I don't know, do you?)

If the answer to both those questions is "yes" then don't create ebooks that will crash the target devices.
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Old 06-09-2014, 01:14 AM   #3
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It was never about the image size, but the size of the uncompressed XHTML size... Even current e-ink readers will become slower when the file becomes larger. As for most books a chapter will not hit that mark, it is usually not a very big issue.
Images can be larger.
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Old 06-09-2014, 01:33 AM   #4
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Quote:
Originally Posted by eggheadbooks1 View Post
For the longest time we've all had to keep our images in ePubs below the 300KB limit, with 260KB the norm to account for differences in the way ereaders read image size.
It's the individual XHTML files you need to keep within the limit. Image sizes can be larger than that.
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Old 06-09-2014, 03:16 AM   #5
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Quote:
Originally Posted by eggheadbooks1 View Post
For the longest time we've all had to keep our images in ePubs below the 300KB limit, with 260KB the norm to account for differences in the way ereaders read image size.
All? I've never done that. Since my devices didn't have this limitation, I simply ignored it. I tend keep my images under 1000 pixels, but I may change that when I get a higher resolution device.

I create ePubs. Those who have devices with additional restrictions can use e.g. calibre to make the conversion.
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Old 06-09-2014, 04:00 AM   #6
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Quote:
Originally Posted by Toxaris View Post
It was never about the image size, but the size of the uncompressed XHTML size... Even current e-ink readers will become slower when the file becomes larger. As for most books a chapter will not hit that mark, it is usually not a very big issue.
Images can be larger.
Quote:
It's the individual XHTML files you need to keep within the limit. Image sizes can be larger than that.
But is WAS about image size, too: every auto-convertor from Calibre to writer2ePub has compressed or downsized images to fit within the recommended 260KB limit when building an ePub. Writer2ePub would even warn users if their images were larger than 255KB (might still but I haven't tested it in 2 years). And when I first learned about this stuff from the developers, I was told the 300KB limit/260KB recommendation applied to images, not just to the individual XHTML file size. If either exceeded 300 KB then some ePub devices would crash or fail to load.

So back to the question: at what point can we, or must we, deprecate this?
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Old 06-09-2014, 08:29 AM   #7
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Quote:
Originally Posted by eggheadbooks1 View Post
But is WAS about image size, too: every auto-convertor from Calibre to writer2ePub has compressed or downsized images to fit within the recommended 260KB limit when building an ePub. Writer2ePub would even warn users if their images were larger than 255KB (might still but I haven't tested it in 2 years). And when I first learned about this stuff from the developers, I was told the 300KB limit/260KB recommendation applied to images, not just to the individual XHTML file size. If either exceeded 300 KB then some ePub devices would crash or fail to load.

So back to the question: at what point can we, or must we, deprecate this?
No, it was not about the image size. I don't care what the Writer2ePub is saying, it is not true. It is only the XHTML. Large images were not useful back then, but that is more about the dimensions than the size. Sure, large images would take longer to load, but not crash.
I have one of those older devices and I usually have images larger than 300kb, never a problem at all. XHTML, yes.

If you really want to have larger images than for example 1200 pixels (and that is no issue on the older devices) in lenght, you can always create a HD version.
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Old 06-09-2014, 11:44 AM   #8
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The only image limitation I have seen is at about 4MBytes for the image size. Some devices can't deal with a file bigger than this. Of course the 260K is about text not images and relates to the way a full chapter (file) is read into memory and then formatted for display.

Of course early MOBI formats had a much smaller limit for images.

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Old 06-09-2014, 12:04 PM   #9
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On my 650, I've been using as high as 1500 line cover images downloaded from Amazon. No issues at all with the cover displaying.
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Old 06-10-2014, 07:30 AM   #10
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I have the same Sony Reader as Toxaris. It is very convenient in size, so I don't want to replace it and will not do just to read someone's book. I'd find some other book than use one that required me to read it on a computer or tablet.

Epubs with over large files will show up on my PRS-300 as having one page and if you try to open them, I believe try cause a reset which can take 5 minutes to recover from.

These sorts of suggestions tend to come from people in the Apple ecosystem where they and everyone they know has ipads. The irony is, according to Hitch, that is NOT where the market for ebooks is, Apple users buying maybe 5% of all ebook purchases, if I remember correctly.
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Old 06-10-2014, 10:58 AM   #11
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My Astak PP (MRSDK based) chokes on a number of Apple mandated things that many older EPUB devices never imagined having to deal with.

<rant> EPUB3 is about Multi-media, not a traditional BOOK that has static images and text. Leave my books alone!
</rant>

I will use my EPUB 2 device as long as I can. It fits my hand with the BUTTON controls in the correct place for reading with 1 hand (the next page button on my K4NT is just a bit off.
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Old 06-10-2014, 12:33 PM   #12
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I have the same Sony Reader as Toxaris. It is very convenient in size, so I don't want to replace it and will not do just to read someone's book. I'd find some other book than use one that required me to read it on a computer or tablet.

Epubs with over large files will show up on my PRS-300 as having one page and if you try to open them, I believe try cause a reset which can take 5 minutes to recover from.

These sorts of suggestions tend to come from people in the Apple ecosystem where they and everyone they know has ipads. The irony is, according to Hitch, that is NOT where the market for ebooks is, Apple users buying maybe 5% of all ebook purchases, if I remember correctly.
Like I said, larger images are not a problem at all, it is about the XHTML. My T1 can open XHTML files larger, but it gets a lot, lot slower untill a page change can even take a whole minute or more. So even for newer devices it is not recommended to have large XHTML files.
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Old 06-10-2014, 05:47 PM   #13
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In most cases, there is no need for larger XML flows. Most books have chapters that are not outside the specification for mobile ADE.
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