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LENSES: Facts and Fallacies - Part VI
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PostPosted: Mon Apr 14, 2014 3:26 pm    Post subject: LENSES: Facts and Fallacies - Part VI Reply with quote
Light fall- off (vignetting ) is a phenomenon that affects all lenses, but to a greater degree, the fast and wide angle lenses. The designer of a fast lens purposely reduces the diameter of the front and rear elements to prevent the horrific aberration that would appear if the very inclined light rays were not eliminated. The result is the so-called optical vignetting (see wikipedia for more details).

Today, vignetting can be eliminated or at least reduced by post-processing. Many cameras already do this automatically for specific lenses. Therefore, vignetting is no longer as big a problem as it was at the time of the film. However, digital technology has introduced a type of vignetting that did not exist before: pixel vignetting. This type of vignetting appears, for example, when someone tries to use extreme wide angle lenses for rangefinder cameras on full-frame cameras. In that kind of lens, the light rays leave the lens in an excessively inclined direction, incompatible with digital sensors. The result is a tremendous vignetting , accompanied by blurring , color fringes and color changes at the image edges






to be continued...

Last edited by Gerald on Sun Mar 05, 2017 5:37 pm; edited 1 time in total


PostPosted: Sun Apr 20, 2014 9:04 pm    Post subject: Re: LENSES: Facts and Fallacies - Part VI Reply with quote
Gerald wrote:
Light fall- off (vignetting ) is a phenomenon that affects all lenses, but to a greater degree, the fast and wide angle lenses. The designer of a fast lens purposely reduces the diameter of the front and rear elements to prevent the horrific aberration that would appear if the very inclined light rays were not eliminated. details)...


Vignetting is one way to reduce image problems on the edges/borders.
But furthermore cosine fourth vignetting is natural cause of vigmetting for wideangle lenses - normally the iris opening looks like a smaller oval form from the side. With help from the Slyusarev effect in lens design this can be eliminated

Gerald wrote:
...
pixel vignetting. This type of vignetting appears, for example, when someone tries to use extreme wide angle lenses for rangefinder cameras on full-frame cameras. In that kind of lens, the light rays leave the lens in an excessively inclined direction, incompatible with digital sensors. The result is a tremendous vignetting , accompanied by blurring , color fringes and color changes at the image edges
..


Microlens Vignetting and crosstalk between pixel are a big problem -see all those who like to use rangefinder wideangle lenses - even on the Crop NEX cameras.


PostPosted: Sun Apr 20, 2014 11:43 pm    Post subject: Reply with quote
Gerald didn't write what he posted, he pasted what he posted. The author is Lester Lefkowitz.

You should blame Gerald for ideas you don't agree with.
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