Wide-angle: the Achilles' heel of SLRs?

E. von Hoegh · Nov 19, 2012

David Lyga said:
Wiltw quote: "back when computers were not used for lens design"

My question: What was the year that things changed? Or please give a short continuum of years defining the (sudden or gradual?) 'improvement' in zooms due to computer determination of formula, as opposed to manual determination. My rudimentary guess is the 'late 70s'. - David Lyga

Dead Link Removed

Poisson Du Jour · Nov 19, 2012

Diapositivo said:
[...]
Distorted means deformed, wrong, weird, not-straight.

:confused:
You talkin' about me while I'm playin' with my glo-flies (instead of cameras)!?

Diapositivo · Nov 19, 2012

David Lyga said:
Wiltw quote: "back when computers were not used for lens design"

My question: What was the year that things changed? Or please give a short continuum of years defining the (sudden or gradual?) 'improvement' in zooms due to computer determination of formula, as opposed to manual determination. My rudimentary guess is the 'late 70s'. - David Lyga

Throughout the early Eighties old-school "hand-designed" lenses coexisted with computer-generated lenses. I think by 1985 most lenses were computer-designed. I remember a lens test showing a recent Nikon SE lens performing much better than the more expensive, heavier, old-design Nikkor. (OK it was heavier also because it was better realized mechanically). Must have been 1985 or so.

I think it was just at that time that Leitz made an agreement with Minolta for the realization of their first zooms (based on Minolta designs). Leitz being a small, quasi-artisanal firm did not have or could not afford a research centre able to deal with the new design tecniques, I imagine. Computer-aided design made zoom lenses possible for photographic purposes. Until then they were basically only seen in the motion picture industry or in small movie cameras. "Turrets" or "bifocals" were the alternatives.

Ed Bray · Nov 19, 2012

This image was taken on my Canham MQC 5x7 using a 72mm Super Angulon (circa approx 16mm as regards 35mm) with a yellow filter. No lens correction was carried out in PS.

Venford Dam 72mm SA XL yellow 5x7 1200 Wet by Ed Bray, on Flickr

wiltw · Nov 19, 2012

David Lyga said:
Wiltw quote: "back when computers were not used for lens design"

My question: What was the year that things changed? Or please give a short continuum of years defining the (sudden or gradual?) 'improvement' in zooms due to computer determination of formula, as opposed to manual determination. My rudimentary guess is the 'late 70s'. - David Lyga

The really powerful yet relatively affordable minicomputers, like the Digital Equipment Corp VAX computer, really came about in the mid 1970s. The much less affordable IBM 360 mainframe had been out about 10 years earlier, but not in broad use...I remember that in 1969 my bank (Wells Fargo) had to make phone calls from branch to branch 30 miles apart, simply to verify that I had enough money in my account to get a $20 cash withdrawal (back when $20 could buy 66 gallons of gas!).

Not being an optical designer, I would have to guess about when computers became much more prevalent among lens designing companies, and more ownable outside government and defense circles. It seems that short ratio (2:1)zoom lenses became much better about the mid 70's, so I speculate that was the result of more computerization becoming part of the design process, rather than slide rules!

georg16nik · Nov 19, 2012

Diapositivo said:
.....Computer-aided design made zoom lenses possible for photographic purposes. Until then they were basically only seen in the motion picture industry or in small movie cameras. "Turrets" or "bifocals" were the alternatives.

1959 - Voigtländer Zoomar 36-82/2.8 for Bessamatic, Exakta, Contax, Pentax, Kodak mounts.
Not computer aided, as far as I know.

Ian Grant · Nov 19, 2012

David Lyga said:
Wiltw quote: "back when computers were not used for lens design"

My question: What was the year that things changed? Or please give a short continuum of years defining the (sudden or gradual?) 'improvement' in zooms due to computer determination of formula, as opposed to manual determination. My rudimentary guess is the 'late 70s'. - David Lyga

It's ongoing but accelerates in the 90's and then speeds up in the past 10/12 years. These changes mean both types of wide angle lenses improve, the Cosina made WA's for range finder cameras are outstanding optically.

I use a 17mm Tamron SP (my second) although I'd buy a 21mm Leitz lens for my M3 if I needed a lens like this for commercial use (with film). I much prefer the 21mm Leitz lenses but would buy a Cosina eqivalent if the budget was too tight however I can't justift it these days as I rarely use 35mm.

Ian

AgX · Nov 19, 2012

David, in Germany the first computers to calculate lens designs were applied in the late 50's.

However these first applications were rather calculations than designing. As the early computers were more related to what we now call calculators than those selfsustained computers aiding in lens design today.

Poisson Du Jour · Nov 19, 2012

Olympus introduced its own optical computational metrics by proprietary computer in mid-1973 and began the task of creating the retro-focus inverted 6E/5G optic of the XA, released in July of 1975. The design of that camera was evidently unorthodox, and the compromises that had to be made to fit a very sharp lens into a small space were formidable for that time (the question asked is, who else did the same thing, eliminating just about all of the sever forms of distortion and aberration, AND which wasn't a fold-out design?), though commonplace today (and often better) in many RFs.

Diapositivo · Nov 19, 2012

I think at the time the designers designed a zoom lens based on intuitions and knowledge/witchcraft, then had to make calculations to verify/understand lens behaviour. With zoom lenses (zoom proper, lenses that perform at all focal lenghts) these calculations take a huge amount of time, considering the great number of lenses and the very great number of "positions" (zoom, focus, aperture), and computer helped make this calculation allowing the designers to figure out much faster at which focal length a problem might have appeared, modifying the design, calculating again etc. This "trial and error" procedure was certainly much faster with computers.

Bill Burk · Nov 19, 2012

I used to think of the Pentax Super Takumar 35mm f/2.0 (with 67mm filter ring) as a rectilinear wide angle lens. Was I mistaken? Or is this really an attribute of that lens?

After it was stolen, I "replaced" it with the Olympus Zuiko 35mm f/2.0 lens. I wasn't thrilled that I was introduced to barrel distortion. So I never really took a liking to that lens, and I kept thinking I should get the shift lens... not at all for the shift feature... but because I had the impression it was bound to be rectilinear.

lxdude · Nov 19, 2012

AgX said:
However these first applications were rather calculations than designing. As the early computers were more related to what we now call calculators than those selfsustained computers aiding in lens design today.

A very important distinction. The early computers replaced mathematicians who did calculations manually; they did them much faster and less expensively. This led to more complex designs being attempted, because the calculating power was there to facilitate them; before then they were impractical or unprofitable.

Later computing power improved to the point that they could support the programming necessary to become design tools.
Large cost reduction has also come from a reduced need for prototypes.

David Lyga · Nov 20, 2012

Very understandable about the advancement of zoom optics and what I really thought: that this computerization of design was largely gradual, emanating (seminally) from 'helping' to calculate and verify the manual efforts, then gradually segueing into actually BEING the 'person' who formulates the data.

Might I ask another question: I heard long ago (two decades) that varifocal lenses were actually sharper than zooms because they had to be refocused with each change in focal length. Has the quality of today's zooms negated that 'advantage'? - David Lyga

Diapositivo · Nov 20, 2012

As a side notation, the best lenses as far as correction of distortion and of field curvature are usually lenses for "reproduction stand" normally to be found in 50mm and 100mm, often called "bellows" lenses because they don't have a focusing helicoid and must be used in conjunction with a bellows (they would normally focus at infinite, with their bellows).

AgX · Nov 20, 2012

In case is true that Parfocal lenses have less abberations, the ability with Varfocal lenses to focus with a long FL and to zoom then back to a short FL, and by this gaining higher focussing acuracy, might compensate in some cases for any better lab-performance of Parfocal lenses.

E. von Hoegh · Nov 20, 2012

Bill Burk said:
I used to think of the Pentax Super Takumar 35mm f/2.0 (with 67mm filter ring) as a rectilinear wide angle lens. Was I mistaken? Or is this really an attribute of that lens?

After it was stolen, I "replaced" it with the Olympus Zuiko 35mm f/2.0 lens. I wasn't thrilled that I was introduced to barrel distortion. So I never really took a liking to that lens, and I kept thinking I should get the shift lens... not at all for the shift feature... but because I had the impression it was bound to be rectilinear.

I'm wondering about this, too. I inherited my father's OM equipment, among which is the OM 35mm shift lens (and a few other goodies).

My experience so far has been that the faster and/or wider the lens, the less likely it will be rectilinear. I have the 35/2 Nikkor-O, and it seems pretty good - but I don't use it for architecture.

RalphLambrecht · Nov 20, 2012

Ian Grant said:
ItA better example although MF not 35mm would be a comparison of the 38 mm Biogon on the Hassleblad SWC with the 40mm Distagon for the regular Hasselblads.

goodpoint!i have the latter, not the former. is there any significant difference?From someone who has bothkeeping in mind that the distagon is a fle design, it might actually be better, at least close up.

Poisson Du Jour · Nov 20, 2012

Michael R 1974 said:
It depends on how it was designed of course. One always hopes a shift lens is designed with architecture in mind, meaning it would be well corrected for distortion, but it depends on the lens. Take the Nikkor PC-E lenses for example. The 85mm and 45mm are virtually distortionless as expected (particularly in the 85mm focal length). The 24mm has visible barrel distortion near the edges. The Canon 24mm TSE-II on the other hand has virtually zero distortion.

True also for Canon's TS-E 24 f3.5L first geneation PC lens. These lenses are designed from scratch to be free of distortion; they have to be: why build a PC lens for architecture if it is going to have distortion as a visible fault?

Old-N-Feeble · Nov 20, 2012

A side jump, I know, but aren't virtually all modern wide-angle large format lenses retro-focus designs? Reduced angle at which the the lens must illuminate the corners is the obvious advantage and was already mentioned. I don't know if this outweighs any disadvantages to the design or if it's more about catering to buyers. My point is that there are no mirrors or other obstacles between the lens and film in view cameras so retro-focus designs must be pretty decent if current production wide-angle lenses are all of this design.

E. von Hoegh · Nov 21, 2012

Old-N-Feeble said:
A side jump, I know, but aren't virtually all modern wide-angle large format lenses retro-focus designs? Reduced angle at which the the lens must illuminate the corners is the obvious advantage and was already mentioned. I don't know if this outweighs any disadvantages to the design or if it's more about catering to buyers. My point is that there are no mirrors or other obstacles between the lens and film in view cameras so retro-focus designs must be pretty decent if current production wide-angle lenses are all of this design.

No.

Old-N-Feeble · Nov 21, 2012

E. von Hoegh said:
No.

Please try to be more succinct.

AgX · Nov 23, 2012

AgX said:
In case is true that Parfocal lenses have less abberations, the ability with Varfocal lenses to focus with a long FL and to zoom then back to a short FL, and by this gaining higher focussing acuracy, might compensate in some cases for any better lab-performance of Parfocal lenses.

I just relized that I mixed up the terms Parfocal and Varifocal in that posting!

The correct version:

In case is true that Varifocal lenses have less abberations, the ability with Parfocal lenses to focus with a long FL and to zoom then back to a short FL, and by this gaining higher focussing acuracy, might compensate in some cases for any better lab-performance of Varifocal lenses.

David Lyga · Nov 25, 2012

Thank you AgX for the change. It's true that there is an advantage to being able to focus 'at telephoto' and then zoom back to 'wide' but, to tell you the truth, sometimes I feel better re-focusing at that 'wide' length. Chalk it up to paranoia perhaps but I really wonder how accurate even Parfocals are with regard to 'holding that precise focus' at all focal lengths. I guess that is what it must really be on my part: paranoia.

Thank you for the clarification, AgX, and also to the others for the necessary addenda to my original question. There is so much to gain on this forum from many with different dimensions of knowledge out there. - David Lyga

Wide-angle: the Achilles' heel of SLRs?

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