IQ of 7d w 15-85mm Vs 6d w 24-105mm?

Started Mar 8, 2013 | Questions thread
Mako2011 MOD
Forum ProPosts: 14,973
A little confused
In reply to qianp2k, Mar 12, 2013

qianp2k wrote:

technic wrote:

usedtobedontrustme wrote:

Here is some conjecture on my part. I would think that an a asp-c camera with an asp-c lens gets more magnification from the lens and imprecisions in the less would be more conspicuous under the scrutiny of the magnification. However, I'm confesson that I never took a lesson.

Yes, an APS-C lens needs to be more precise for the same IQ. But reality is that it is often easier to make small lenses to better perfection, for a reasonable price. Look at the tiny lenses from e.g. some Panasonic/Leica lenses on the Panny TZ, they often have very high optical quality. But it is impossible to say such a thing in general, because there are lots of factors involved (e.g. homogeneity of the glass and surface finish, precision of the internal lens threads and mounts, etc.). Most of that is related to the lens design / the type of lens.

Actually it's more challenge to design native lenses for smaller sensors.

It seems you got a tiny bit confused or simply mixed up the two sizes. Understandable.

EF-S and DX lenses are designed for the smaller image circle of the small sensor.  The sensor is 22.2mm x 14.8mm (just one example), which has a diagonal distance of 26.7mm. This is why if you put an EF-S lens on a full frame camera you get a circular sharp image with a dark outer area.

Designing a lens for a larger image circle is harder. It typically uses more lens elements and more expensive ones because of the need for more aspheric or special glasses to keep the image sharp and evenly lit over the larger image circle. This makes the lens larger, heavier and more expensive. Basically it comes down to this, creating a lens for the smaller sensor is easier and cheaper than it is for the big sensor at the same level of lens performance. This is also the case with lenses for medium and large format cameras.

Smaller is cheaper for good reason

Hope that helps clear it up. Good luck

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My opinions are my own and not those of DPR or its administration. They carry no 'special' value (except to me and Lacie of course)

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