Down the font rabbit hole I go

[Colonel Cathcart]

Up until recently I use(d?) to read with the publisher default font. I did side-load some fonts, a few Hebrew fonts but also a few other that were recommended repeatedly on the forum like Boookerly and Literata Book.
The other day I decided to force using one of them and after a bit of switching back and forth decided on Bookerly, and boy-oh-boy the reading experience is more joyous than ever.
There is, however a little problem I'm experiencing. Well, maybe two. I read kepubs, and Bookerly-Italics just renders very much like Bookerly-BoldItalics. So as a first step I updated the font to the latest version, 1.201 from a kindle firmware. That did do anything. I got Extremis, Domestic: EPUB Feature Peeker and loaded two versions of it to my device, an epub and a kepub. You can see how it renders yourselves in the screenshots attached.
Funny enough, searching for Bookerly in this font modding thread people are mostly complaining that the font is too light. It appears I need to change the weight but by how much? Is it possible to create a test kepub with different weights to test them out side by side?

btw, I also noticed the difference in ligatures (or lack there of) between the two screenshots (very clever choice of word, office, well done!) and since turned on optimizelegibility in the Kobo config file. Now I'd also like to turn on Kerning, if possible, for kepubs.

So to sum up my questions:
1. Can anyone recommend by how much I should change the font weight and how? I understand that Font Forge increases the font size so I'd better use font tools? is that correct?
2. Is it possible to create a font weight kepub/epub test document to try different weights side by side?
3. Can I turn on Kerning in general or for a certain font for kepub?

[Sirtel]

Kobo has weight adjustment built in, why not use that?

[Colonel Cathcart]

Originally Posted by Sirtel

Kobo has weight adjustment built in, why not use that?

Because it adjusts the weight of the entire font family. When they're present in the text, side by side, regular next to italics, it'll still look wrong. regular Bookerly looks fine as it is, I don't want to change it's weight, just Bookerly-Italics.

[jackie_w]

@Colonel Cathcart,

The Bookerly bold/italic issue is a known problem when using Bookerly on a Kobo. It is fixable if you want to take the time and trouble. The solution is documented in the Kobo Wiki. The example used there is Amazon Ember but the technique can be used on any font which displays the same symptoms.

btw, I also noticed the difference in ligatures (or lack there of) between the two screenshots (very clever choice of word, office, well done!) and since turned on optimizelegibility in the Kobo config file. Now I'd also like to turn on Kerning, if possible, for kepubs.

The optimizelegibility setting should enable both ligatures and kerning in kepubs. This does, of course, assume that the font you're using contains both those features.

[Colonel Cathcart]

Thank you, jackie_w, just the info I needed. It looks fine now. Also, learned a thing or two while doing it, which is always a plus.