I realize that something I posted to pixls.us works as a kind of Summary of Findings. So I thought it might be interesting to share it here.
In addition to the many good comments, I’ll throw in my $0.02 worth. Keeping mind anything I say is worth the price you paid for it (ie: $0).
From looking at lenses for going on four decades to find a certain “magic”, here’s what I’ve learned.
Until surprisingly recently, lens designers I’ve talked with felt that correcting for 7th order effects, while “do-able”, was a little over the top. People told me it was “unnecessary.” Modern optics can be corrected for 11th or, gasp, 13th order effects. There are a few interesting reasons to do this now.
In general, vintage lenses typically were designed for either resolution or contrast. Modern optics can be found that strike an interesting balance between resolution and contrast (see previous paragraph). Which leads me to think the computing required to design lenses for 11th order effects was rather too great for rooms filled with human calculators (see Nikon’s 1000 and 1 Night series).
In the vast majority of imaging systems I’ve looked at, resolution limitations are found in light sensitive materials (ie: film or digital sensor) and not in the lenses themselves when operating at their optimum aperture. OK. That’s a strong caveat, but someone sent me years ago a 75mm f/8 wide angle lens that covers at least 4x5 inches that is diffraction limited from wide open. So “softness” at wide apertures for some vintage optics is there because they’ve been designed this way.
This is why I feel many vintage lens manufacturers designed their optics to a customer base (sort of). I’m thinking of old Nikon optics where they were designed for under-corrected spherical aberration behind the point of focus as well as providing a veiling spherical aberration wide open. This was, I’m convinced, deliberate to satisfy the Japanese market which valued a “delicacy” of rendition. Canon OTOH went the over way because of their customer base and over-corrected for spherical aberration behind the point of focus. Old Canon lenses can appear sharp wide open, but deliver nasty soap-bubble-ish background rendition as a result. Pentax, again in broad, designed their lenses to be more neutral.
Modern Voighlander Heliar lenses bear little to zero rendition resemblance to lenses made for large format film in the early to mid 20th century. Which is to say, be careful of thinking naming conventions will render a scene similarly across the ages. Another example of what i mean is anything labeled “Sonnar.” How well a lens is corrected is more a function of careful design. Don’t believe me? Compare early Zeiss, mid-century Soviet, and the (justifiably) highly regarded 10.5cm/105mm Nikkor-P “Sonnar” designs. Out of focus rendition, chromatic aberration, flare, and astigmatism are treated widely differently depending on who designed the lens and is not something inherent in the basic optical layout. The Kingslake comments previously noted elsewhere in this thread about the Tessar formula being another excellent example. I’ve not encountered such a consistently horrid lens (and I’ve owned far too many of them) as the Zeiss 50mm f/3.5 or f/2.8 Tessar coming from the former Eastern Bloc. They blew it. It never gets “sharp”, really. f/8 seems the best it can do for an acceptable image.
Modern optics can suffer from a surprising level of field distortion (barrel or pincushion). It appears to me that lens designers sometimes rely rather strongly on software to correct this kind of distortion since it makes it easier/cheaper to correct for chromatic aberration, astigmatism, and flare. In general, vintage lenses can be surprisingly “rectilinear” and I’ve not found it necessary to lean heavily on distortion corrections.
Many vintage and most modern optics appear to offer pretty good field flatness. Zoom lenses can be another matter, particularly those designed for SLR and early DSLR. No, not all suffer from this, but I can pretty much find a weak spot in just about any zoom. There’s nearly always a “hole” somewhere in the zoom range, or so it seems.
Even knowing all these things, trying to see an advantage of one thing over another can be difficult. I would enjoy buying a beer for the person who could sit down next to me and tell me which image was made with which lens. It’s impossible, of course. But because we’re on the “inside” and it matters to us, we often place a LOT of emphasis on the lenses we choose. I can’t tell the difference between images made with a new Sigma 24mm f/3.5 DG DN and an early '80’s Nikon Nikkor 24mm f/2.8 Ai. I could say similar things about just any of the lenses I own, vintage or modern.
So after all these years and all this thrashing and whinging and wrangling where did I find the “magic” I was looking for? I found it in careful image processing. This means tightly controlled color management, color grading, sharpness and local contrast controls, etc, etc, etc. This means being clear with myself on what I seek in and how to express a subject/scene in the final result.
OK. Enough of that. There’s much more I could say, but why? I’ve already said too much.
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