Is there a mathematical way to figure out frame fill?

I'm curious to know whether there is a mathematical way to predetermine/approxima​te the increase or decrease a subject will fill the frame at X distance when using different focal lengths.

In an attempt to get some numbers to work with, using my old 28-70 that has a distance scale, I took 3 quick snaps of my daughter, and positioned her head in the vf to be about the same size (forehead at upper AFP, chin at lower AFP), at 28mm, 35mm, and 70mm. The distances were approximately 2.5'@28mm, 3.25'@35mm, and 5'@70mm. I think it may be related to AOV, as (I think) by making her size similar in each shot, I essentially gave each FL the same AOV from her forehead to her chin. Is that right?

This is one of those 'no real need to know' type of things, but I think it can be useful to know the math side of it. Or maybe I just have to much time on my hands.....

I just google.... not expert at all

http://en.wikipedia.or​g …_camera.27s_fie​ld_of_view

Ok, that gives me a start.

On APS-C, 29mm lens sees 29 degrees AOV vertically, and at subject distance of 2.9m (100*FL), he frame sees FOV of 1.49m x 22.3m (100*frame dimension)

Convenient, but unfortunately this convenient memory aid has no direct equivalent in other format sizes.

Field of View calculators with readout in AOV or feet/meters per given distance:
http://www.tawbaware.c​om/maxlyons/calc.htm

tzalman wrote in post #14984614
Field of View calculators with readout in AOV or feet/meters per given distance:
http://www.tawbaware.c​om/maxlyons/calc.htm

Great link! Thanks!