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

Started Oct 7, 2013 | Discussions thread
tko Forum Pro • Posts: 12,328
the easy explanation

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.

Visualize half a sphere. Take a small cut of the front. It's almost flat. Take a wider, bigger cut. The curvature is more pronounced. Take a cut almost the diameter of the sphere. You have a very heavy, curved piece of glass.

Worse, that round surface doesn't focus very well. The wider the lens, the more exotic the correction needs to be. It's only nearly flat lenses that can get by with little correction.

A larger sensor needs a bigger lens (well, you could make a slow, small lens for one, but most people wouldn't buy it, because result in compact camera performance.) Those larger sensor lenses are essentially faster, with a bigger front diameter. More $$, more correction, more weight. Now imagine a zoom, with everything sliding and correcting. More compromises, compromises that are harder to achieve with highly curved lens elements.

It's harder to make an elephant do a back flip than a flea. Just a rule of physics. How many medium format zooms are there? In addition, SLR users tend to be a little more picky. Their reference standard is a good prime. Almost by definition, anything else is in second place.

In short, the SLR lens is typically bigger and faster with more highly curved surfaces that need additional correction.

Leandros S wrote:

People say that interchangeable superzoom ("travel") lenses can't manage good sharpness, yet superzoom compacts do just fine in terms of sharpness. Why is that?

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