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Looking at the Soligor, makes me wonder if having such a complex array of elements on the Carl Zeiss one is even beneficial to the lens performance.
Is there really a reason for such a complicated design? This is a serious question, so if anyone can explain this to me, I'd be grateful.
[here's my two cents]
Lens design is very complex. I don't understand how to do it, but I do understand what it gives to me. The conflicting requirements to optimize for evenly distributed resolution, contrast, and illumination across the frame, as well as reducing geometric distortion, colour aberration (CA), and flare, for both near and far subjects introduces many challenges. In order to compensate for and to surpass at least some of those challenges, the design can get very complicated. Simple designs can provide great performance for one or two optical attributes, but inevitably have compromised performance in other areas.
Many 'classic' lenses with relatively simple designs have very desirable and unique characteristics, but if you want a telephoto with excellent IQ from centre to corner, with low CA, and low vignetting, you'll quickly find that all signs point to the expensive lenses with relatively complex designs. TANSTAAFL.
I'll bet you five cookies that the Zeiss is the best lens in that group, for all performance metrics, except maybe weight and cost. The Pentax is a special case. It's a true classic with legendary performance, and it's scarce. A used SMCP-A* 135/1.8 in [E] to [E+] condition will cost you about the same as a new Zeiss Sonnar 135/1.8. I expect the Zeiss has better IQ, but they're a dime a dozen. OTOH, the Pentax might have better bokeh, whatever that is. I'm confident that Alf will help us to figure this out.
Anyway, I've been using the Canon EF 135/2L for many years. It's widely regarded as one of the best 135mm lenses ever made. Its optical design is complex. I suspect that its excellent performance is because of, not in spite of, its complex design. I've included a copy of the EF 135/2L optical diagram below, from the Canon Camera Museum.
I've also included optical designs of the EF 200/1.8L and EF 70-200/2.8L IS II. Both are incredible lenses, and both have complex designs. I once saw my 200/1.8L in an airport scanner. It blew my mind. It looked just like the optical diagram, but 'full size', and much better colour! I asked if I could take a photo of the screen but I got no joy.
Canon EF 135/2L
Canon EF 200/1.8L
Canon EF 70-200/2.8L IS II