E-mount for Nikon MILC, good idea or not?

Started Sep 23, 2017 | Polls thread
snellius Contributing Member • Posts: 911
Re: E-mount for Nikon MILC, good idea or not?

bobn2 wrote:

That's simply wrong, which is what I've been telling you. Since the rear element is refractive, the light does not take a straight path though it. If the rear principle plane is far enough back, a small element can illuminate all parts of the sensor (albeit, at oblique angles in the corners). The diameter of the exit of the lens is in proportion to its distance from the focal plane. The exit lens for an f/1.0 lens needs to be 12mm if it's 12mm away from the focal plane, 18mm if it's 18mm away and 46.5 mm if it's 46.5 mm away, and so on, if the rear principle plane of the lens is at the exit lens. Place it further forward, and it gets bigger if vignetting in the corners is to be avoided (which is one reason that 'design for digital' lenses have tended to restrict maximum apertures). For the F-mount, which gives a minimum distance for the rear element of 38mm, and has a clear diameter (with a slim contact block) of 37.5 mm (not off Wikipedia, just measured for myself) that gives a minimum achievable f-number of 1.01, which one could call 1 between friends. In practice f/1.2 shouldn't be a problem with an E type lens and a more sensible contact block than Nikon's standard design. For the E mount, with the same diameter and a smaller register, it clearly isn't a problem, a Nikon f/1.2 on an adapter can do it, so build on the adapter and there you are.

And also a deterioration of the shape of the bokeh circle in the corners (even narrower cat eyes). Or even worse if the shape of the opening is not round, but also contains a lens contact unit, you may also see it in the bokeh circle.

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