Originally posted by Mistral75 Digital sensors need lenses of telecentric design, i.e.that ensure low, image-sided, raypath angles. Digital sensors do not 'like' sharp incidence angles of the rays at the edge of the image, which cause vignetting, blur (because of crosstalk) and colour shifts (usually magenta colour shift).
A retrofocus design is an example of quasi-telecentric design.
Thanks for the explanation, Mistral!
---------- Post added 08-08-14 at 12:05 PM ----------
Originally posted by ElJamoquio And a lot of the reason mirrorless lenses aren't really all-that-much smaller or lighter than DSLR lenses.
Well, the Fuji wide angles are smaller and lighter, EJ, it was pointed out in another thread, because of the short registration distance.
The teles are presumably harder to engineer.
---------- Post added 08-08-14 at 12:07 PM ----------
Originally posted by Pål Jensen Neither a 2.8 lens or a 2 lens is an 1.8 lens.
Aperture is not defined from DOF but from exposure. Ie the amount of light reaching the sensor/film.The aperture is proportional to the square root of the light admitted, and thus inversely proportional to the square root of required exposure time, such that an aperture of f/2 allows for exposure times one quarter that of f/4.
I think the actual definition is the ratio of focal length to aperture diameter, Pal, rather than DoF or exposure.