How does one access optical sizes in LibreOffice?

Question

I am a big fan of LibreOffice, because it is both free and powerful – powerful enough to give you complete access to all OpenType features. I am not sure whether optical sizes is something that is actually part of the OpenType specs, but I do know that good fonts come with at least two, usually preferably three optical sizes. The font of choice for me is EB Garamond.

Here is the problem: Anyone writing an historical or classical text, will want footnotes; these are usually set in a smaller font size (usually 10 points versus 12 points body text). However, I today realised that the font I am using is using the same optical font size for both 10-point and 12-point sized text, vz.:

Figure 1: Comparison of font shapes for EB Garamond for seven different point sizes. Image created by typing the sample letters in LibreOffice, then applying the different zoom levels to see the letters at the same on-screen size.

As the image demonstrates, the optical font size is exactly the same, irregardless of point size. I should mention that the reason I am expecting different optical sizes, is because the first iteration of the font (which only got developed to v. 0.16), included EB Garamond 12 and EB Garamond 08. The current iteration of the font is, as far as I know, a continuation of the work done by Georg Duffner. I would expect it to include at least two optical font sizes. I do not have any software with which to inspect fonts, and so my only method is to make visual comparisons as above.

How can I access the different optical sizes of a font via its OpenType features? Given that LibreOffice simply uses the CSS tags to access them, this would apply both to web design and word processing. It could of course be that the current version of the font doesn’t include multiple optical sizes, but that is beyond my means to investigate. The font should choose the correct optical size for any given point size.

Note: I would suggest the new tag optical-size, but I do not have enough reputation to do so.

Relevant: TTF and other “modern” font systems, and font size differences

Answer 1

The font family you've got doesn't include optical sizes: Pardo's family which added bold weights only uses the 12pt optical size.

EB Garamond 08 is a totally separate set of fonts, which only exist in Duffner's original version. You can download them here. The files to install are otf files EBGaramond08-Regular, EBGaramond08-Italic and EBGaramondSC08-Regular for small caps if you want. There are no bold styles for the 8 point optical size.

Some variable fonts have an optical size axis, but I'm not sure if there are any major apps which automatically select the right optical size. In any case it's not relevant here as EB Garamond isn't a variable font family.

EB Garamond is a great family; seeing it in 2014 (gosh, seven years ago!) really got me to realize how timeless Garamond's work is, and how well serif fonts can fit into the future of typography on the web! However, the more I used it I started to see the limitations (lack of weights and display optical sizes) and things that may be historically right but may seem weird to modern readers (quite tight spacing between characters in particular). These aren't dealbreakers but if you want a whole-package digital Garamond I do recommend checking out Adobe's Garamond Premier Pro at $299. No, it's not free, but considering the number of styles that's quite low by modern font family standards, and it really does give you everything. The Display Light optical size in particular is to die for, it's based closely on Garamond's largest "gros-canon" font and looks stunning.

If you want a free family with optical sizes, best to check out Adobe's Source Serif by Frank Grießhammer or Newsreader from Production Type/Google Fonts, although neither is very like Garamond, both are more rugged and higher x-height.