MobileRead Forums - View Single Post - are PDFs smaller in size than EPUBs in general?

Quoth · 11-18-2022, 09:14 AM

What Turtle writes ^^^^^

Something is wrong with the epub. Perhaps it has Asian fonts or fonts with Asian glyphs not subsetted.

Or maybe the cover & subcover are huge and got resized in the conversion.

Simplified
1) An epub is a zip file with an index file, a file that's a list of files used, 1 or more HTML files, optional CSS files, optional font files, optional image files. You can rename it to .zip and extract to see the sizes. Or use the Calibre Editor. Regular epub has no concept of pages. The app or device's renderer creates pages on the fly a little like setting a paper size and print preview in a Web Browser. No built in headers or footers. Each HTML file is purely sequential and a control file has the order for the display of the files.

2) A PDF is a kind of envelope. It can have pages and layers. Content can be any mix of raster images, vector images, Postscript, text, fonts. Content isn't sequential but has information on which page and layer. Pages have a physical size. Layers can have transparency. A particular resource might not be displayed sequentially but the items (even down to a single letter) can have placement instructions.

So if all else is equal (and it almost never is), there is little difference between a PDF with text content rather than image based pages and an epub.

Some of my files for one book

odt for docx & epub 2.1 M (fonts not embedded). Primary version. Only this is edited for content.
docx for epub 2.1 M (fonts not embedded)
epub 3.4M (has embedded fonts)
mobi 3.0 M
azw3 4.2 M (has embedded fonts)
jpeg cover 0.9 M (the upload cover for ebook publishing is huge, 7.5 M and for paperback wrap cover is 16M, source is 26 M).
odt for export as PDF 4.1 M (fonts not embedded). Only format or styles are edited.
pdf for paperback is 7.3 M (no cover, includes fonts).

So not much difference. There are 10 images in epub (some are small like QR code & logo). About 160,450 words.
The odt for PDF export has headers, footers and is about 590 pages excluding front matter & contents (about 10 pages).

If you have a 20 M epub and 2 M byte PDF, then one or other is broken.

Also what is the PDF for? An epub is superior for all screens (or mobi for Kindle before 3.4 otherwise azw3 for Kindle). Use Lithium (or Pocketbook if text to speech needed) on Android, some equivalent on iOS (not Apple app "Books"), or some other Android app for Android 3 or 4!

The only use for a PDF version of an ebook is paper printing or paper publishing. Or maybe for a reMarkable or Sony Digital Paper as those are PDF only eink tablets for annotating PDFs with scribbles.

11-18-2022, 09:14 AM	#3
Quoth Still reading Posts: 14,352 Karma: 105899727 Join Date: Jun 2017 Location: Ireland Device: All 4 Kinds: epub eink, Kindle, android eink, NxtPaper	What Turtle writes ^^^^^ Something is wrong with the epub. Perhaps it has Asian fonts or fonts with Asian glyphs not subsetted. Or maybe the cover & subcover are huge and got resized in the conversion. Simplified 1) An epub is a zip file with an index file, a file that's a list of files used, 1 or more HTML files, optional CSS files, optional font files, optional image files. You can rename it to .zip and extract to see the sizes. Or use the Calibre Editor. Regular epub has no concept of pages. The app or device's renderer creates pages on the fly a little like setting a paper size and print preview in a Web Browser. No built in headers or footers. Each HTML file is purely sequential and a control file has the order for the display of the files. 2) A PDF is a kind of envelope. It can have pages and layers. Content can be any mix of raster images, vector images, Postscript, text, fonts. Content isn't sequential but has information on which page and layer. Pages have a physical size. Layers can have transparency. A particular resource might not be displayed sequentially but the items (even down to a single letter) can have placement instructions. So if all else is equal (and it almost never is), there is little difference between a PDF with text content rather than image based pages and an epub. Some of my files for one book odt for docx & epub 2.1 M (fonts not embedded). Primary version. Only this is edited for content. docx for epub 2.1 M (fonts not embedded) epub 3.4M (has embedded fonts) mobi 3.0 M azw3 4.2 M (has embedded fonts) jpeg cover 0.9 M (the upload cover for ebook publishing is huge, 7.5 M and for paperback wrap cover is 16M, source is 26 M). odt for export as PDF 4.1 M (fonts not embedded). Only format or styles are edited. pdf for paperback is 7.3 M (no cover, includes fonts). So not much difference. There are 10 images in epub (some are small like QR code & logo). About 160,450 words. The odt for PDF export has headers, footers and is about 590 pages excluding front matter & contents (about 10 pages). If you have a 20 M epub and 2 M byte PDF, then one or other is broken. Also what is the PDF for? An epub is superior for all screens (or mobi for Kindle before 3.4 otherwise azw3 for Kindle). Use Lithium (or Pocketbook if text to speech needed) on Android, some equivalent on iOS (not Apple app "Books"), or some other Android app for Android 3 or 4! The only use for a PDF version of an ebook is paper printing or paper publishing. Or maybe for a reMarkable or Sony Digital Paper as those are PDF only eink tablets for annotating PDFs with scribbles.