comprehensive: lagom.nl...
    Adjust the display until all of the segments in the following strip are distinct
    and their intensity is uniformly differentiated. 
    
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | a | b | c | d | e | f | 
Use this link to: evaluate gamma...
    The following links (full-bleed, solid-colour pages) are useful to determine uniformity, dead pixels, &c.
    For best results, use full-screen mode.
    
black : k | white : w | grey : e | red : r | green : g | blue : b | cyan : c | magenta : m | yellow : y
You can use access keys to select the colour pages (e.g. k for black); h returns here.
The following gradients are useful to determine linearity. They should appear smooth, without banding.
 
        full (0–100%) · dark (0–50%) · mid (25–75%) · bright (50–100%)
 
        r (0–100%) · g (0–100%) · b (0–100%) · rgb (0–100%)
 
        
        gb (cyan) · rb (magenta) · rg (yellow) · rgb (black)
        (This is the inverse of the rgbw gradient above.)