Originally Posted by davidfor
You could set a fixed font size in the ePub. Is that what you are doing for the Sony? I don't see a "small" option anywhere in the conversion options. Or is this a Sony driver option?
I think the reference to "small" is the Sony device font-size setting (small, med, large on a PRS505).
As far as I can tell, the difference between Sony and Kobo re: font-size is that the Kobo changes font-size by replacing whatever is in your css body style with one of its 24 font sizes, which look as if they are set in absolute points (or pixels???) which are non-scaleable. I believe the Sony's settings use a scaling factor to change sizes. As you probably know, Calibre always creates css body font-size in em units (base font-size 12pt equates to 1em, 15pt to 1.25em etc). Because em units are scaleable, with some experimentation, you can set the Calibre base font size such that it looks "perfect" for you when viewed at Sony size "small" (or "medium" or "large").
Or to get the ultimate font-size control on an older Sony, you can install PRSPlus which will let you create your own on-device css files with whatever font family/size/line-height/margins you want and which can (usually) be made to override whatever is in the epub's own css file. The PRST1 has a similar but different hack to achieve the same thing.
BTW I spent a long unproductive evening trying to manually set my epubs' css body font-size to get finer size control on the Kobo Glo. It didn't work so I've settled on using an SQL trigger kludge to be able to set 'unavailable' font-sizes from the Kobo.