You can't tell from the diagrams. They are very simplified, do not show precise curvature, do not show the type of glasses used, do not show exact spacing...
They might fine tune them differently, but when the diagrams look identical, I'd say they are copying each other. Besides, the CAPA 2003 lens catalog have fine printed diagrams.
Tessar from one company looks the same as Tessar from another company (yet their performance might differ greatly). Your typical 6/7 1.4/50mm lens has about the same diagram as another 6/7 gr/el 1.4/50mm lens. But in fact, that's just because they evolved from the same design, and are today the peak of that design. Modern lenses like Leitz's turned off from Gaussian design, just because it was "depleted" of novel design ideas.
I looked at all the 50mm diagrams, they look different. Sorry.
Your typical 2.8/14mm lens is very probably the same design as well, you just can't make such ultrawide in many different ways. You just tweak it here and there.
Sigma & Canon look very different. Have you actually checked their diagrams?
Rumors like that surface time to time, and mostly, are meaningless. Not that 3rd party lens makers can't make excellent lenses, they can - given enough money, though.
Give me a break. Have you actually checked their diagrams, again?
Alan Chan http://www.pbase.com/wlachan
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