Update: As of Backlight 3.2 you can now change the fonts size in the page template. Look in your page template under Content > Main Copy. You’ll see Font-size and Line-height options that will let you increase or decrease the value for each setting. There is also a Custom option that will allow you to enter a value in pixels.
But if you’re still on an earlier version, read on….
In Backlight, the standard body font size is 16px. That’s baked in and there is no control to change it. Everything else is based from that using em or rem. Except specific areas where we have control over font size.
It looks like the .the__copy selector controls the main copy areas (1em) and .widget controls the pallets (0.875em)
(note that there are two underscores in .the__copy)
So you can use those selectors in your custom css to adjust the size. If you wanted 18px fonts for the main copy, you can do either this:
.the__copy {
font-size: 18px;
}
Or
.the__copy {
Font-size: 1.125em;
}
I think that .the__copy should be specific enough. If you only want to make the change to specific sections of a page, you can write the copy in html and add the styling inline:
</pre>
<p style="font-size: 1.25em;">Your text....</p>
You can also target specific pages or page or album or album set templates by using classes found in the body tag.