New answers tagged optics
12
The fundamental driver of cost in a lens is not the correction of aberrations, although the correction of aberrations does add to the cost of a lens, and may be a more significant factor in wider angle lenses. Generally speaking, the primary cost of a lens is the "glass". I put glass in quotes, because sometimes it is other materials, such as Fluorite or a ...
4
You've probably heard people describe some lenses as "unusably soft wide open, but passable at f/2.8 and excellent from f/4", or similar. That's because, basically, these lenses are already designed in the way you suggest, although additionally constrained by size, weight, complexity, cost, and other design factors. And they also let you use the lens at ...
2
The extra glass in a fast lens is not just there to correct aberrations. The full aperture must be visible across the whole field of view meaning for moderate or wide lenses, you can't just make the aperture larger you'd have to make all elements in front of the aperture much larger as well.
But your idea is sort of in effect with large format lenses. Many ...
2
There's one teensy-weensy little flaw in the plan: the aberrations (particularly, but not solely, spherical aberration) are the main culprit for the phenomenon of focus shift. Essentially, that would mean that your "focusing lens" won't have exactly the same focal length as your "taking lens", so images focused perfecctly at the larger aperture will be out ...
2
Actually, in-body apertures have existed on interchangeable-lens cameras, and in a way that allows lenses of different focal lengths to have common maximum apertures. Perhaps the best-known camera to do this was the Pentax Auto 110, a 110-format film SLR. Pentax went that route with the Auto 110 because it would be sturdier and less complex than trying to ...
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