Are lenses for smaller sensors inherently cheaper to make at the same quality?
Asked 8/26/2014
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In theory, should a lens designed for a smaller sensor be cheaper than an equivalent-quality lens for a larger sensor? My intuition is that using only the smaller central part of the image circle should make aberrations such as vignetting, distortion, coma, and chromatic aberration easier to control. In other words, cropping the center of a full-frame image usually removes the worst edge defects, so does a smaller sensor relax the optical design enough to reduce cost or complexity?
Assume comparable sensor technology and pixel pitch, so the smaller-sensor lens is not being asked to compensate for a worse sensor. Is the answer different in practice once factors like aperture, field of view, and manufacturing scale are considered?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
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It's only the image circle that changes, really. Everything else either remains the same or becomes a bigger problem (for instance, the need for even wider apertures for the same depth of field at the same angle of view and subject distance means that greater degrees of correction will be required for things like coma, spherical and chromatic aberration). (A 40mm f/0.85 lens for Micro Four Thirds -- which exists, and costs $2000 -- is the functional equivalent of a $500 85mm f/1.8 on 35mm "full frame", or almost, since it's a little slower.) The largest elements of the lens have to remain the same, and you don't gain a whole lot of cost savings reducing the image circle -- it's not zero savings; it's just not as much as you might think, especially when the difference between sensor sizes isn't huge. And that savings will be applied to the dubious "feature" of putting back the vignetting you lost not using a lens with a larger image circle.
On the other hand, lenses of lesser quality might not display quite so many problems on a smaller sensor, so in that sense lenses for smaller sensors can be cheaper. (Imagine what the barrel distortion of an APS-C 18-to-whatever lens would look like on a full frame sensor.)
Originally by user28116. Source · Licensed CC BY-SA 4.0
user28116
11y ago
0
Generated from our catalog & community — verify before relying on it.
Generally, yes in theory—but not by as much as people expect, and not always in practice.
A smaller sensor needs a smaller image circle, so the lens only has to maintain good performance over a smaller image height. Since many aberrations grow with field height, this can make edge correction easier. If you scale a design down while keeping the same angle of view, optical performance can improve and the lens can use less glass.
But equivalent lenses are not simply “the same lens with the edges chopped off.” To match the same angle of view and depth of field on a smaller format, you often need a shorter focal length and sometimes a wider aperture, which can make aberration correction harder again. Also, the largest elements may not shrink as much as expected, and a finished lens includes motors, mechanics, and housing that do not scale down proportionally.
So: smaller-format lenses can often be lighter, smaller, and somewhat cheaper, because the image circle is smaller and glass volume can drop a lot. However, the savings may be modest once equivalent aperture/performance requirements and non-optical manufacturing costs are included.
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