Making a superzoom for a compact is easy, but for a DSLR, it's hard?

Started Oct 7, 2013 | Discussions thread
OP Leandros S Senior Member • Posts: 1,970
Re: the easy explanation

OpticsEngineer wrote:

"Optical designers could give you a more complex answer, but the simplest way to visualize it is that a lens is a curved surface. The bigger the lens, the more the surface has to curve."

That pretty much is it. And rays out on those more curved areas suffer a lot more spherical aberration. So then you have to use additional elements or aspherical elements to correct that.

Transverse spherical aberration increases as a cubic power with lens diameter. Which means lens designs just fall apart when you increase the diameter. It often comes up with question like, "Your 20 mm diameter design is really good, can we increase that to 30 mm, that isn't a big change is it?" But usually it is a huge change.

Thanks for answering the original question. I didn't realise that there was a power law behind it all. If I had set this up as a question, I would now mark yours as the answer. Cheers!

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