After several years of using FCP5, 6, and 7, I've started creating all my new projects in FCPX. In earlier releases, I created my titles, lower 3rds, and credit rolls in Boris Title3D and Title Crawl, in which I specified the font sizes in points. Since Boris generators aren't provided with FCPX I am reconstructing all of my text clips in the new release.
In the FCPX Title generators, the "Size" value doesn't seem to be in points...at least the number is quite a bit higher in FCPX than in FCP7 for letters that appear to be about the same height in the Viewer window. For example, one of my titles uses the Copperplate font. In FCP7, the size was 42 pts, while in FCPX it's 114 pts. Another line in that same title uses Arial. In FCP7, 28 pts; in FCPX, 70 pts.
What units of measurement does FCPX use for text size, and how can I relate that to the point size that I used in FCP7?
Point size for a text used in a title depends on the size of Motion Template used to make the title.
This means if the title was created at 1920 by 1080 and used in a 1080p timeline, the type size should be correct: 1080pt type is approximately the height of the screen (depending on typeface design). If that same template is used on a 720p or 480p timeline, the whole template is scaled down to match the timelines, so text set to 1080pt in the template will match the height of the screen.
This applies if a Title was created at 720p. If it is used in a 1080p or 4K timeline, 720pt will still type will fill the screen (there's no text quality degradation when scaling up).
Most Title motion templates are created at 1080p, so when used in lower resolution timelines, type sizes will seem smaller than in Final Cut Pro 7 and earlier.
In practice, Final Cut Pro 7 type is too large in 1080p timelines - the effective resolution isn't 1 point per pixel.
For example, for an upper case A to fill the screen in 7, the size of Gill Sans type must be set to 525 points. In Final Cut Pro X titles created at 1080p in 1080p timelines, the size must be set to 1572.
So when working in 1080p, you must triple the sizes you're used to when moving from 7 to X.