Scrivener's .mobi files bloated?

I’ve been exporting a Scrivener book to a .mobi format using the compile function. In general it’s working perfectly, but I did notice one thing that’s odd.

When I export the book using Scrivener to .mobi the finished .mobi file is around 9mb.

When I take that same .mobi file, open it in Calibre and ‘convert’ to .mobi (something that I have to do to remove the PDOC tag so that the book appears properly on the new Kindle fire: details here if you really want them … indle-fire) then the file is all of a sudden just 3mb - a third of the size!

When I load the smaller .mobi file onto my Kindle, it appears identical to the Scrivener file. So why is the Scrivener file 9mb and the Calibre version 3mb?

Anyone know?

Incidentally, if I use Scrivener to export to .ePub and then use Calibre to do the .ePub -> .mobi conversion, both the .ePub and .mobi files are about 6mb.

Again, I don’t see any difference between the 3 file sizes… but there’s obviously something!

9mb, even 3mb is huge for an e-book. It’s got to be some kind of media that is causing these differences, as that would be a truly massive chunk of useless data if it were a text problem. Do you have a lot of figures in this e-book, is the cover image very high res? I’m wondering if Scrivener, using QuickTime for its media handling, is letting some huge files pass through that a program like Calibre is automatically compressing or deducing the DPI of to optimise for what e-books need? QuickTime doesn’t really know anything about good usage on an e-reader, and is in fact more optimised for professional graphics and media work, and so wouldn’t think anything of a 6mb cover graphic.

Scrivener doesn’t use QuickTime for image handling - that’s only used for video and audio handling and hasn’t got anything to do with images in Scriv. But Scrivener does indeed know nothing of the images themselves or of their compression - if you import a JPG or PNG image and use that in the e-book - whether for the cover or images inside the book itself - Scrivener will do nothing to compress them, as it makes no assumptions - or rather, it assumes that if you have imported a JPG or PNG image for inclusion in your book, then you want it included as-is. It may be that Calibre is compressing or reducing the images of these image files. So you may just need to reduce the quality of these files before importing them if you want to reduce file size - definitely take a look at how large your imported images are (in file size), anyway, as that is the most likely explanation.

All the best,

Oops, sorry for the mislead, I’m not sure what I was thinking about with QuickTime, but as Keith points out the gestalt is the same. It will do what you tell it to do. A good rule of thumb for e-book images are a maximum pixel dimension of 800 tall by 600 wide, at 72 DPI, using RGB, and for best results, profiled to sRGB. That would be for an image that fills the entire average e-reader screen, like a cover image or a full page diagram.

Stop laughing and you wouldn’t do things like this.

Inside joke folks. Sorry.

It could be the images. There are a few of them in the book (it’s an instructional guide, not a novel, so has more pictures to illustrate concepts). I’ve already downsized all the images to a mere 500px wide but maybe they are 300 dpi? I’ll check…

Incidentally, the latest Kindle recommendations are for images that are:

-300 dpi (to future proof content - already I’ve seen rumours of an iPad with a 300 dpi screen)
-at least 600 x 800

I think I know what it might be: in Calibre you can choose a ‘profile’ to export to such as for iPad or for Kindle. I think Calibre resizes the files, depending on that profile. When I resize for iPad, I get a bigger file than if I export for Kindle.