Digital BW, The Print

I don't think this is off topic, I am certain someone somewhere has 
quantififed this. Any thoughts on what the ideal viewing height range 
is for framed mounted prints in a gallery setting?  Frames will be up 
to 30" x 20" or 750 x 500mm.  I'm thnking there is a sweet spot from 
45" to 80" or 1m10cm to 2m.

Thanks,

Chris