Hello all, longtime optical designer here.

[koraks]

I understand. But sometimes, there are other protective measures in place (not necessarily planned) that stand in the way of reverse engineering. There can for instance be specific assets (tangible or intangible) involved in relation to the complexity of the device or solution that make it difficult or even impossible to replicate the solution. But we digress.

 

[jonesmi]

We will,most likely , have thousands of questions for a guy with your experience. Here is my first: the Nikon 105mm f/2.5 comes as a Sonnar and as a Gauss version. Is there any objective reason why one would be better than the other?

Not having the actual designs in hand, all I can say with credibility is that a change to a cheaper glass, or one that hadn't been discontinued, may be the driver. Changing from a costly fluorocrown to a newer one, or a discontinued abnormal crown glass (KzFSN2, for example), are possibilities. Weight reduction, shift in center of gravity, or simply a better design are possible reasons. Sorry to be less informative than we both want me to be.

 

[Jarno]

Regarding Ralphs question, and without being an optical designer (but a mechanical engineer), how do you define "better"?
Engineering is about tradeoffs, like indeed weight reduction, material choices, sharpness, corrections, maximum aperture, cost, what is important to you might be irrelevant for another user.

 

[jonesmi]

It turned out that anyone with enough money can purchase your device and reverse engineer it. of course with a patent paper in hand, that gets even easier, or the patent paper raised the awareness in the first place. Patents can be counterproductive.

I have 15 different patents. I have been infringed on two of them, but since I patented my creations as an employee and the employer paid for the claims and filing, it was their property. That also meant that I would not see rewards from any patents, just a paycheck. They chose to not fight the infringements. So as someone here said, I simply showed industry how to do something and steal it.

 

[4season]

Hi Mike,

Like others here, it'd be fun to hear opinions of lenses you consider amazingly good, but not just costly and exotic ones, but also (if you know of any) cheap and common ones which made you shake your head in disbelief at how the designer achieved so much with so little.

 

[Jarno]

I have 15 different patents. I have been infringed on two of them, but since I patented my creations as an employee and the employer paid for the claims and filing, it was their property. That also meant that I would not see rewards from any patents, just a paycheck. They chose to not fight the infringements. So as someone here said, I simply showed industry how to do something and steal it.

Not even a financial incentive? Sheesh, I think I got something like 1500 euros for my two patents as the company I worked for had a programme to reward registration of IP.

 

[Individual One]

It turned out that anyone with enough money can purchase your device and reverse engineer it. of course with a patent paper in hand, that gets even easier, or the patent paper raised the awareness in the first place. Patents can be counterproductive.

In the situation that I was referring to, the details in the patent application were so complete and accurate that it seemed to some of us very likely that the (gigantic and well funded) customer had suborned an employee/employees with detailed knowledge of our product to assist in their efforts, apart from having the resources to purchase a device to examine.

 

[RalphLambrecht]

Not even a financial incentive? Sheesh, I think I got something like 1500 euros for my two patents as the company I worked for had a programme to reward registration of IP.

It's not uncomon. the general justification is: you are employed and paid to have good ideas and whatever you dream up on company time is automatically company property. After all the company pays for all patent fees and upkeep. Incentives are a generous option but not a must.

 

[Eishwaneeren]

Interesting. FWIW, I've been using such lenses for decades and still don't know how to recognize aberrations in my photographs.

That sounds amazing in a concerning sense.

 

[Eishwaneeren]

Put stars in the center, sides and all four corners of the field. This will directly show you your point spread functions (PSFs) across the FOV, and even show focal plane tilt on large format cameras. I can post up some representative PSFs of astigmatism, coma, lateral color and so forth so you can compare them to what you image.

Have you ever treated that as a standardised test? Also, which hill station should I go to for that?

There's something about pictures that have defects, unfocused areas, and other antique parameters that make them aesthetically attractive, yet technically they're awful

Are they technically awful when they invoke the imagination of what can be corrected?

 

[Dan Fromm]

That sounds amazing in a concerning sense.

Excuse me. Which aberrations should I be able to see in my photographs and under what conditions?

I can see distortion in photos of USAF 1951 charts, not in photographs of real world subjects. This with one fast double Gauss type and with one heliar type. I can't see coma, spherical aberration, etc. in either. I can see lower resolution far off-axis, but not its causes. I have seen astigmatism in shots of grids with an horrible mirror lens but with no other lens.

All this with anastigmats -- tessar types, dialytes, heliar type process lenses, double Gauss, sonnar types, dagor type [f/6.8, f/7.7, f/14), ... -- shot reasonably stopped down. I don't shoot wide open.

What do you do to make aberrations visible? Lens types, shooting apertures, subjects, please.

 

[loccdor]

It's not uncomon. the general justification is: you are employed and paid to have good ideas and whatever you dream up on company time is automatically company property. After all the company pays for all patent fees and upkeep. Incentives are a generous option but not a must.

The financial incentive is smart because it helps discourage someone from hiding their idea and claiming later that they didn't develop it while working at the company.

 

[Eishwaneeren]

Excuse me. Which aberrations should I be able to see in my photographs and under what conditions?

I hope that didn't touch a wrong nerve. Aberration is very common (and very bad) with budget/middle-tier budget vintage lenses on new bodies.

edit: afaik it sets off color accuracy to a horrible degree (I shot last year only on vintage lenses on my Fuji camera, leading to photos i didn't have any time to edit). It is caused due to what I believe is called chromatic-type aberration. Obviously you know better than me but you must have meant aberrations in ideal situations (same era of body & lens) — which is very difficult to spot without trained eyes. I apologise if you misunderstood me.

 

[Dan Fromm]

I hope that didn't touch a wrong nerve. Aberration is very common (and very bad) with budget/middle-tier budget vintage lenses on new bodies.

edit: afaik it sets off color accuracy to a horrible degree (I shot last year only on vintage lenses on my Fuji camera, leading to photos i didn't have any time to edit). It is caused due to what I believe is called chromatic-type aberration. Obviously you know better than me but you must have meant aberrations in ideal situations (same era of body & lens) — which is very difficult to spot without trained eyes. I apologise if you misunderstood me.

Thanks for the reply. I still don't understand what you're getting at.

So you'll know, I've seen chromatic aberration, negligible as in making it visible and obnoxious requires considerable magnification, with a 200/4 MicroNikkor AIS on my D810. This was never a problem with that lens when shooting KM or ISO 100 E6 films. Remember, the sensitive surface can make a difference but the box it lives in shouldn't.

I've also seen horrible color shift -- strong blue cast -- with a pre-WWI B&L f/6.3 Tessar on ISO 100 E6. A reshoot found none. Natural daylight in both shots, but in the first blue one the sun was behind a cloud and in the second it wasn't.

Roses are red,
Shadows are blue

Retest before concluding that the problem is the lens.

 

[Steve Goldstein]

A note on patents...

Patents are little more than bargaining chips for many large corporations. I used to work for a large electronics company that had thousands of patents including a handful of mine. Our main competitors had similarly large patent portfolios. Generally speaking, the patents protected the companies, but not in the way you might think.

With multiple corporations fiercely competing in a limited space it's almost impossible not to occasionally infringe without knowing it. We'd report infringements to the legal department and usually they'd appear to do nothing. Every so often one company would launch an infringement lawsuit against another over an allegedly-infringed patent they thought particularly valuable. At that point, the accused party would open their file drawer to pull out a stack of their own patents the accuser was infringing. After a suitable amount of legal harrumphing the companies would settle, cross-license the patents in question, and move on. Things almost never went to trial.

It can be different in small companies and in newer fields. When my employer was a baby company they acquired a collection of well-written broadly foundational patents that they used to block significant competition for many years. They also had closely held trade secrets (think Coca-Cola formula, but in electronics). Those patents are now expired and after a couple of decades others managed to duplicate the function (though not the specifics) of the secret sauce, but these complementary forms of IP allowed my employer to become and remain one of the 800-pound gorillas in its field.

By the way, we were reimbursed an amount when the application was filed and a larger amount if and when the patent issued. Not every great idea was filed, a committee decided which ones might be worth the non-trivial legal fees. It's just as well: doing a good patent application is a lot of work that must be done outside one's project schedule, and while the extra money was nice, somehow it never seemed enough for the amount of extra work it entailed.

Now, back to our discussion of the 105mm f/2.5 Sonnar-vs-not Nikkors. As a Nikon owner I'm also curious about this.

 

[warden]

A note on patents...

Patents are little more than bargaining chips for many large corporations. I used to work for a large electronics company that had thousands of patents including a handful of mine. Our main competitors had similarly large patent portfolios. Generally speaking, the patents protected the companies, but not in the way you might think.

With multiple corporations fiercely competing in a limited space it's almost impossible not to occasionally infringe without knowing it. We'd report infringements to the legal department and usually they'd appear to do nothing. Every so often one company would launch an infringement lawsuit against another over an allegedly-infringed patent they thought particularly valuable. At that point, the accused party would open their file drawer to pull out a stack of their own patents the accuser was infringing. After a suitable amount of legal harrumphing the companies would settle, cross-license the patents in question, and move on. Things almost never went to trial.

It can be different in small companies and in newer fields. When my employer was a baby company they acquired a collection of well-written broadly foundational patents that they used to block significant competition for many years. They also had closely held trade secrets (think Coca-Cola formula, but in electronics). Those patents are now expired and after a couple of decades others managed to duplicate the function (though not the specifics) of the secret sauce, but these complementary forms of IP allowed my employer to become and remain one of the 800-pound gorillas in its field.

By the way, we were reimbursed an amount when the application was filed and a larger amount if and when the patent issued. Not every great idea was filed, a committee decided which ones might be worth the non-trivial legal fees. It's just as well: doing a good patent application is a lot of work that must be done outside one's project schedule, and while the extra money was nice, somehow it never seemed enough for the amount of extra work it entailed.

Now, back to our discussion of the 105mm f/2.5 Sonnar-vs-not Nikkors. As a Nikon owner I'm also curious about this.

One company that I worked for early in my career would award me one celebratory dollar bill for each patent issued. It wasn’t about the money, it was about saying thanks to a valued employee in a public way. Later in my career as a consultant there were no rewards at all other than the fee paid by my clients, so my name is on the patents as inventor and they are named as the assignee. Simple.

@jonesmi Welcome!

 

[grant.goodes]

We will,most likely , have thousands of questions for a guy with your experience. Here is my first: the Nikon 105mm f/2.5 comes as a Sonnar and as a Gauss version. Is there any objective reason why one would be better than the other?

If you are not aware, there's a great description of the 105/2.5 lens design and history here. To quote the author, Haruo Sato, a lens-designer at Nikon: "Compared to the previous model with Sonnar type lens construction, it offers significant improvements in close-range aberration fluctuation, as well as peripheral light, spherical aberration and coma. In particular, it delivers a beautiful balance of focused and defocused (blurred) images, as well as higher resolution with natural gradation. The Xenotar-type lens design with the ideal aberration correction made it the perfect lens for portraits."

These are clearly different optical designs, with the Sonnar being the original version dating back to the Rangefinder era, and grandfathered in for the F-mount from 1959 until it was replaced by the double-Gauss "Xenotar" version in 1971 (lasting until it was discontinued in 2005). Nikon changed the optical design to achieve specific goals, so one would expect there to be differences based objectively on the design updates they made.

I have an AI'ed copy of the last run of the Sonnar lens and also an AiS copy of the Xenotar, so have been able to compare them. This is not truly an apples-to-apples comparison, as all Sonnar 105's are single-coated, and my Xenotar is from the final run of the lens incorporating Nikon's (then) most advanced SIC multi-coating. I definitely find my Xenotar to superiour to the Sonnar at close-focus, and of course much less prone to flare (understandable given that the Sonnar is single-coated). I was never much of a Bokeh guy, but the Sonnar seems to have a more painterly background blur, while the Xenotar has a cleaner look, but that is pretty subjective. I think the Sonnar is probably a nicer rendering for wide-open/portrait shots, and that is probably the use I would make of this lens, and otherwise I'll be sticking with my AiS copy (smaller, lighter, and with a nice built-in hood).

 

[Eishwaneeren]

Thanks for the reply. I still don't understand what you're getting at.

So you'll know, I've seen chromatic aberration, negligible as in making it visible and obnoxious requires considerable magnification, with a 200/4 MicroNikkor AIS on my D810. This was never a problem with that lens when shooting KM or ISO 100 E6 films. Remember, the sensitive surface can make a difference but the box it lives in shouldn't.

I was talking about chromatic aberration/bringing. That is usually very visible, so I was confused when I read about you not being able to spot aberration.

 

[jonesmi]

Aberrations aren't an issue for low magnification prints, like 35mm to 5x7. Aberrations mostly interfere with print image quality in high-magnification enlargements, with lateral chromatic aberration on color prints usually being the most obvious.

 

[Dan Fromm]

I was talking about chromatic aberration/bringing. That is usually very visible, so I was confused when I read about you not being able to spot aberration.

There are other aberrations.

 

[reddesert]

Welcome jonesmi. There are many times where optics and their compromises are discussed on the forum and it would be interesting to have the perspective of an experienced optical designer.

I hesitate to jump into a back-and-forth in a welcome thread, but to the question of whether / which aberrations one should be able to see in pictorial use. Most of the time for a lens within its design envelope it should be hard to see aberrations, because they've been minimized by the designer. But for example pushing outside the envelope, like using a non-macro lens with a lot of extension for macro/close-up work, may reveal significant aberrations. Also, some typical aberrations will be much more obvious at fast apertures, if you work at f/8 there will be less to see than at f/2.8.

An example of a visible aberration is when lenses show "swirly bokeh." This is caused by tangential stretching of the out of focus image toward the edges of the field, I've more or less assumed that it's undercorrected astigmatism, although there could be other factors.

An experienced optical designer can tell you about the tradeoffs that are made in a design, or maybe address questions about practicality to manufacture. Like a couple of random examples:

- why do certain types of process lenses made for 1:1 also generally perform well at infinity (eg. dialytes / Artars) and others don't (my understanding is that "wide field" process lenses and those fast oscilloscope lenses often don't)?
- did Schneider really have to give making the Angulon because they couldn't get the glass types any more?

I work in a related field and can read an optical design textbook, but there's no way I could answer these kind of practical questions.

 

[ic-racer]

I've been doing optical design since 1972, including university, photographic, defense and astronomical optics. I'd love to discuss camera lens design here, with an emphasis on large-format lenses. These lenses fascinate me, and I'm interested in how well lens aberrations are controlled in historical and contemporary lenses. Nice to meet everyone!
Mike

Aren’t large format lenses some of the easiest to design due to the smaller reproduction ratios required during printing.

 

[Prest_400]

Aren’t large format lenses some of the easiest to design due to the smaller reproduction ratios required during printing.

That's what I found interesting, that the larger the format, the less demands on the lens due to the reproduction ratios. Having said that, I'd be curious for really high performing (35mm alike) medium format and large format lenses. Be squeezing all off every square milimeter of the film!

I had been thinking, that a modern standard double gauss design in 35mm pars up with a Tessar type of a medium format, say of 8x10" prints side to side. Have had roughly that and a TMX 35mm roughly appears equal to a medium format HP5 frame. I am mostly a Medium format shooter, and tend to look up to the higher performance double gauss lenses that were used after the 50s (Planar, Xenotar, Fujinons etc).

Also, as of writing this, it appears that the Plasmats are a common design in LF whereas smaller formats standardised on Double Gauss. Seeing the schematic I can see that both are related but the Plasmats appear limited to f5.6 so that perhaps made them uncommon in the smaller formats.

Quote from the folder thread. Might be a bit out of context, but relates as to how smaller formats converged in quality with time.

Folders are niche because an old folding medium format camera won't necessarily give you more detailed pictures than a 35mm film camera from this millenium.

Great pages! Much very interesting stuff about the evolution of the Tessar, too. https://zeissikonveb.de/start/objektive/normalobjektive/tessar.html

Fascinating read!

 

[ic-racer]

Looking forward to following your posts.