Billboard Myths

wiltw said:

The lens only delivers so much resolution...assuming a spectacular lens of 120 line-pairs per millimeter, if you blow that up 40x, that leaves only 3 line-pairs per millimeter on print. It takes 5 line-pairs per millimeter on print for the eye and brain to perceived the image as 'sharp'. If you back up to 40X your usual viewing distance, your eye and brain will once again be fooled into perceiving the image as sharp.

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blockend said:

Correct. Cropping is a last resort. In film days Pros would often crop their 6 x 6 finder to A4 format for publication (15% reduction), now people expect to point any lens at a distant bird, plane, whatever, and fill the frame (400% reduction). It's no substitute for a longer lens.

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