Conversion Lossy or Lossless?
 

Being fairly new to the ebook world, please forgive me if this question is elementary. When you do a conversion of an ebook from one format to another, is there anything lost in respect to formatting? For example if I took a mobi file and converted it to epub and then converted that epub back to mobi, would the final file be exactly the same as the original or would it have lost something in the transition? I use this as an example but would assume the result would be the same pdf/epub/pdf or mobi/pdf/epub/mobi.

That really depends on the formats involved. Many ebook formats are basically some subset of (X)HTML in some sort of wrapper. However, the various subsets are not all the same, for example, ePub supports formatting that MOBI doesn't support. So it really depends what your source and destination formats are, but generally, I'd assume that formatting will get lost. That said, Calibre tries hard to preserve what formatting there is.

Also note that the examples given included pdf as an intermediate format. Converting anything from pdf is often extremley lossy.

Adding to the 'losses' list :p
The reader software can just plain ignore valid formatting instructions.
ADE is great at this.
:bulb2: Just browse Calibre and the various reader brand sections on MR and you will see the questions (and, sometimes, work-around)

in my (limited) experience, it is best to treat epub as your master format.

it has more features than mobi & because it is open source it is easy to manipulate & hopefully future proof.

so I aim to get everything looking good in epub, then I convert to other formats as needed using default conversion settings -

(Sorry for posting in the wrong forum)

Thanks to everyone that replied. Bit by bit I'm slowly learning about this technology.

It depends on the formats and the program used for conversion. Also, some formats have more features/options than others--if you convert epub to mobi, you'll lose whatever line spacing, fonts, and css features that were in the epub; converting back won't restore them because mobi doesn't have those options.

Converting through PDF is always a bad idea. PDF is a page-based format, and some PDF creation programs strip out formatting; their goal is to make a printable page, and the metadata that notes "paragraph" separate from "line placed this far down on the page" is missing. Converting from PDF can wind up with a return at the end of every line, depending on how the PDF was made.

If you have a file you want to be able to convert to multiple ebook formats, starting with a well-made HTML file is probably best. Converting around between ebook types, if there's anything more complex than bold, italics and chapter breaks, is likely to lose formatting info.

Some ebook formats don't even hold that much info; PalmDOC .pbd is basically plain text; if you convert to it, converting back out won't have the original formatting.