Modern photographic objectives are made of multiple lenses with constant refractive index in each. The result is that thickness of an objective is comparable to (and sometimes even larger than) its diameter.

Suppose we can make an arbitrary object with any distribution of refractive index we want (up to discreteness of molecular structure). Let's also limit ourselves to shapes where maximal thickness of the resulting lens would be, say, 100 times smaller than its diameter.

If we were to create such a lens, would there be any physical reasons to be unable to minimize all the aberrations that modern objectives minimize, to the same level of quality? Maybe some conservation laws that would require larger thickness, or something else...

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  • $\begingroup$ In the other extreme, a pinhole is an OK 'objective'. At some point you get into major mechanical issues (including build-in stresses), so one would have to consider a broader range of aberrations than normal. $\endgroup$ – Jon Custer Mar 17 at 16:13

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