helimat wrote:
I have a hot take on that one too..... In the calculations they never seem to factor in focal length, but would the aperture being further from the film plane/sensor not make the angle of the light less oblique?
There is a note on that at the very bottom of the page:
"Technical Note: Independence of Focal Length Since the physical size of an aperture is larger for telephoto lenses (f/4 has a 50 mm diameter at 200 mm, but only a 25 mm diameter at 100 mm), why doesn't the airy disk become smaller? This is because longer focal lengths also cause light to travel farther before hitting the camera sensor -- thus increasing the distance over which the airy disk can continue to diverge. The competing effects of larger aperture and longer focal length therefore cancel, leaving only the f-number as being important (which describes focal length relative to aperture size)."