const COC_TOLERANCE_PIXELS: 1.5
How large a blur circle still reads as a point, in display pixels.
The 1/1500-of-the-diagonal rule every depth-of-field table is built on is a
claim about a 10×8 print viewed at 25 cm. This image is looked at through
whatever drawing buffer the browser has, so the circle of confusion is a
property of the display: gauge · tolerance / height. On a 24 mm gauge over
1520 px that is 23.7 µm, which lands close enough to the 29 µm full-frame
convention to be a sanity check rather than a coincidence — and it moves with
the display the way the blur it predicts actually does.