[Calvertp]

[quote name='wim' timestamp='1285023022' post='3019']

Actually, what you describe is the optical vignetting I was referring to, and I do expect a single filter or the absence of a filter not to have any effect on this either, as a lens normally is designed to take at least 1 filter of a standard size and thickness, without causing mechanical vignetting. You can read a little on optical vignetting here:

[url="http://www.opticallimits.com/lens-terminology"]http://www.photozone...ens-terminology[/url]

Spherical aberration is something completely different; you can read more about it here:

[url="http://toothwalker.org/optics/spherical.html"]http://toothwalker.o.../spherical.html[/url]



Kind regards, Wim

[/quote]



Thanks very much for the interesting links as well as the very instructive discourse. Yes I see that this is still an issue of vignetting. I suppose that the lens would have to be significantly larger (in diameter) to minimize the effect at short focal length and low f number? Yet it is already a behemoth!



All the best.

[wim]

[quote name='Birefringent' timestamp='1285037832' post='3024']

Thanks very much for the interesting links as well as the very instructive discourse. Yes I see that this is still an issue of vignetting. I suppose that the lens would have to be significantly larger (in diameter) to minimize the effect at short focal length and low f number? Yet it is already a behemoth!



All the best.

[/quote]

Actually, it would need to be constructed as a lens with a much wider AoV and much larger image circle, of which only part is used (an example is the TS-E 17 in unshifted and untilted mode), and which possibly will be quite a bit bigger too, yes.



There actually is a direct link between AoV and aperture when it comes to optical vignetting. The wider the lens and the larger the aperture, the more optical vignetting there will be. The main part of the mathematical function for this is a cosine power 4 function, so the amount of vignetting rises rather rapidly towards the corners of the image with an increase of AoV.



Kind regards, Wim