Thought I'd make a summary based on findings in this long thread and some simple calculations for beginners like me. Hope this helps understanding how the FONT_RAMP values correlate to what the kindles show on display as measurable height in mm (approximately, differs a bit depending on the font - I'm using Bookerly on 300dpi PW3)
##### Default values are: #################
7.13 7.81 8.49 9.17 10.53 12.56 16.98 29.2
This translates to
height in px:
19.2; 21.1; 23; 24.7; 28.6; 33.9; 45.8; 78.9
How?
FONT_RAMP value * 2.7 = height in px
How many px per mm are shown on 300dpi PW3/Voyage:
300/25,4 = 11,81px/mm
Height in px / 11,81 = height in mm
Example:
29.2*2,7=78.9
78.9/11.81=6.68mm
##### Some working sets from other users: ########
11.30 11.72 12.14 12.56 12.98 13.40 13.82 14.24
9.33 10.00 10.67 11.33 12.00 12.67 13.33 14.00
12.30 12.72 14.14 14.56 15.98 16.40 17.82 18.24
###### My testing and sets: ##################
7.13 7.81 8.49 9.17 10.53 12.56 16.98 18.24
// Default, but biggest setting (value 8) reduced
// Steps between 4-5 and 5-6 too much; value 1 too small
7.81 8.49 9.17 10.53 12.00 12.56 15.98 18.24
// eliminated value 1 and tweaked the upper middle field
What I'm happy with for now:
7.81 8.49 9.17 10.00 11.33 12.00 14.56 17.82
// further tweaking from middle upwards to smoothen steps
Also interesting read plus cheat sheet to steal more working values from:
https://www.mobileread.com/forums/showpost.php?p=3089345&postcount=42
Thanks to
odamizu, who also explained a bit there how these values are calculated in order to actually work.
More detail about how the kindle values are calculated explained by tono1020:
https://www.mobileread.com/forums/sho...5&postcount=54
// it's a good read for the non-metrics especially. For my testing I found my way easier to handle, though less accurate than tono1020's.