There is no magical size/weight advantage

Started Mar 5, 2014 | Discussions thread
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Re: There is no magical size/weight advantage
In reply to Paul Pasco, Mar 6, 2014

Paul Pasco wrote:

olyflyer wrote:

Paul Pasco wrote:

Physics is physics but a smaller image circle can make a significant difference in the overall design and size of a lens, particularly on the wide end of the spectrum. Compare these two for example: Samyang 10/2.8 APS-C: 86mm diameter, 77mm long and 580 g. Nikon 10/2.8 CX: 55.5mm diameter, 22mm long and 77g. Of course these have totally different equivalentfocal lengths but their actual focal lengths are the same. So I guess in this case at least there is a huge size and weight advantage, if not a magical one.

Yes Paul, but when you enter special area then physics actually change. A fish eye lens can not be compared with a normal lens, just like a macro can not be compared with a non-macro.

Never the less, you are right that there are significant differences up to normal or short macro, but longer the focal length the less the difference is. Remember that most of the differences are in the flange back distance (no need for the FT-1) and the smaller rear elements. The difference for the front element is zero, the total tube diameter can be a bit less for an N1 lens due to a bit smaller parts after the front elements.

The Samyang lens in question is rectilinear not fisheye, in case you aren't aware.

OK, I admit, mistakenly I thought it was a fisheye (I had a Samyang fisheye once for my DX), but never the less, it is so wide that it demands special lenses at the front, so the normal rule for measuring the size of front element is no longer valid. Also, the N1 10/2.8 has only 6 elements while the Samyang has 14, probably for obvious reasons, to be able to make it wide enough. There are other lenses as well, for example the 24-120/4, which also has huge front elements, twice the "necessary" diameter in theory, but even here I guess it is because of the wide angle, and in fact, even if you look at the N1 lenses, the size of front element increases as the angle of view increases, for instance the 6.7-13 seems to have a far too large front element also considering the focal length / aperture ratio.

I think that these discussions can only be held in a general level if the extremes and special lenses are excluded. I have said many times that the small sensor, mirror less systems have size advantages if one ignores part of the equivalence (AOV or DOF) but the size advantage is of course more obvious at shorter focal length, since by omitting the FT1 you gain in many cases a huge size reduction, especially if you ignore the equivalence in all direction, both AOV and DOF.

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