A7r 24-70 vs Nex-7 16-70 vs EM1 12-40

Started Mar 2, 2014 | Discussions thread
OP LTZ470 Forum Pro • Posts: 11,926
Re: A7r 24-70 vs Nex-7 16-70 vs EM1 12-40

Camley wrote:


You raise an interesting point. With regard to the advantage of larger diameter rear element lens, the only info I could find was that the further the rear element has to be from the focal plane, the larger its required diameter. I presume this is for a specific image size.

So an a7 lens that is designed to be as compact as possible, will have a fairly short distance from the rear element to the film plane and will therefore have a smaller rear element than say an equivalent DSLR lenses which must clear the swinging mirror.

If this is correct, equivalent Leica rangefinder lenses should also have fairly small rear elements.

Of course there is nothing, except size, to stop Zeiss designing lenses with greater distance from the rear plane if this would make for an easier lens design. Perhaps the stunning Zeiss FE 55 f/1.8 increases the rear element to focal plane distance to achieve its stellar optical performance.

As a final comment, comparing images from three cameras with different manufacturers, sensor size, sensor MP, lenses and different in-camera processing is a "dogs breakfast". There are too many variables which have to be normalized somehow before you can say which is best.

Thanks for the comments...packing up the 24-70 to send it back to Sony...

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