RustyBug
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 p.118 #1 · which lens has the most 3D POP? | |
Jonas B wrote:
Hi,
I interpret this to mean that you believe the mid-zone dip in Leica lenses is a characteristic that was intentionally designed. That sounds pretty strange to me. Do you have any sources that can confirm, for example, that the mid-zone dip in the Summilux-M 35/1.4 ASPH is intentional?
I have the same question regarding Zeiss (which lenses are you referring to?) which, if I understand you correctly, intentionally designed their lenses to “bake in” transitional rates of change variance for a “typical” landscape scenario. Is that really the case? What does a typical landscape image look like (one that’s well-suited for a Zeiss lens)?
I don’t think I’ve ever considered the characteristics you just described in certain lenses to be desirable. But I’m pretty straightforward: I like it when it’s sharp in the center and from edge to edge; if the quality degrades (and it does), I’d prefer it to do so linearly from the center out toward the corners....Show more →
Hey Jonas.
Unfortunately, I came to this pseudo-perspective more than a decade ago. The unfortunate part is that when I was studying this for my personal understanding, I did not save all the documentation that I found for such things.
For instance, there was a "great shootout" for (28mm or 24mm) that pitted a large fielding of lenses. In the course of the shootout (not mine) there was significant discussion about how to value the transitions through Zones A/B/C ... and credence given to the evenness across the frame for doing so.
Meanwhile, there were articles regarding Leica ethos for specifically designing transition zones for the purpose of "layering" the scene.
Sadly, despite having looked numerous time to find theses sources again, I have not been able to re-locate them. This story repeats itself in a variety of aspects, where I onboarded the information, but didn't retain the source info for posterity.
My studies of the matter were ongoing with my art school work. Had I known there would "be a test" decades later, I might have kept better files. Should I happen to find them ... I'll certainly share with our fellow members.
Although ... I have shared certain aspects of this with direct links to Leica / Karbe / etc. ... and some folks persist to totally dismiss the legitimacy of that source information, so it can be questionable whether or not people actually are trying to understand ... or, are they just desiring to dismiss my position. But, I'll still share because even though there are absolutely ardent folks who take up their position in vocal opposition to mine ... there remain fellow members who "lurk" ... and if my offerings aid them, then I'm good with that, too. 
Again, sorry I don't have that source info ... wish I did.
As to intentional design choices ... Mandler vs. Karbe. 
For optical designers, it's always by intent (even where quid pro quo reigns).
The question is what the intent is ... generic, well corrected, as even across the zones as possible. Or, harness the differences.
As I mentioned before about my 28's (of yore in the EF mount adapted lens heyday), my Oly was most even across the zones A/B/C, my Nikon AIS was most Zone A centric, and my C/Y was somewhere between both of them. Depending on what I was shooting for, I'd grab a different lens, per its zone transitions.
As a brain tickler ... when / why would a lens designer choose to have forward field curvature vs. rearward curvature vs. flat?
How would those choices influence or differentiate (or not) depth perception. How would that be if the subject was bright and the BG dark, with forward curvature vs. rearward curvature. What if the subject / BG tonal values are reversed ... would forward or rearward curvature amplify or offset depth or projection perceptions? What influence would vignetting have? What influence would reduction in contrast / detail have in a given zone?
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