Calculation of the visual acuity limit for the closest distance to sit to your television. Using the defaults, if you plug in the diagonal size of your TV, the value will be (in inches) the closest you can sit to your 1080p television showing 1080p content and not see individual pixels. Equation taken from http://en.wikipedia.org/wiki/Optimum_HD…

gistfile1.py

import math

arcminute = math.tan(math.pi/10800)  # tan(1/60) in radians.

def visual_acuity_seating_distance(diagonal_in_inches, *, native_horizontal_resolution=1920, native_vertical_resolution=1080,
                                    content_vertical_resolution=1080):
    """Calculate the closest you should sit to your television, in inches."""
    return (diagonal_in_inches /
            (math.sqrt((native_horizontal_resolution/native_vertical_resolution)**2 + 1) * content_vertical_resolution * arcminute))
           
def recommended_distances(diagonal_in_inches):
    """"Calculate viewing distance based on some common ratios/viewing angles: 20, 30, and 40 degrees respectively."""
    return diagonal_in_inches * 2.5, diagonal_in_inches * 1.6, diagonal_in_inches * 1.2