Hello all, longtime optical designer here.

[jonesmi]

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

 

[BrianShaw]

Welcome, Mike! You should have a good experience here as optical desing if often discussed. I'll be starting a thread soon on a specific question I have regarding how to use a 19th century lens with an aperture wheel but no markings. Hopefully that will be something you can help me with.

 

[bewilson]

I'm looking forward to these discussions!

 

[Dan Fromm]

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

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

The little voice in the back of my mind wonders why you don't go into databases of lens designs, e.g. OSLO's or the smaller but free one on dioptrique.info, and use your design software to see how well the prescriptions do. I think that dioptrique.info shows how some aberrations vary by angle off-axis.

I understand that prescriptions are idealized representations of lenses as actually made, am having trouble understanding how anything I can report about mine can interest anyone. Except, perhaps, for remarks about distortion seen in, e.g., the few photographs of USAF 1951 test charts I've taken.

 

[cliveh]

Welcome Mike and perhaps you could provide more information about the lens used by Julia Margaret Cameron?

The Jamin lens consisted of two separate groups of elements. It had rack and pinion focussing and a fixed aperture of f 3.6, a design invented by the Hungarian mathematician Joseph Max Petzval in 1840.

 

[jonesmi]

Yeah, me too! I will start posting some camera lens designs and performance as the weeks go by. It's always interesting to me to see how bad these lenses look when analyzed in optical design software, yet they perform beautifully in reality. Or for some lenses, not so much.

 

[Alan Edward Klein]

Yeah, me too! I will start posting some camera lens designs and performance as the weeks go by. It's always interesting to me to see how bad these lenses look when analyzed in optical design software, yet they perform beautifully in reality. Or for some lenses, not so much.

Welcome to Photrio. Do the old designs perform beautifully in a technical or aesthetic sense? There's something about pictures that have defects, unfocused areas, and other antique parameters that make them aesthetically attractive, yet technically they're awful.

 

[jonesmi]

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

The little voice in the back of my mind wonders why you don't go into databases of lens designs, e.g. OSLO's or the smaller but free one on dioptrique.info, and use your design software to see how well the prescriptions do. I think that dioptrique.info shows how some aberrations vary by angle off-axis.

I understand that prescriptions are idealized representations of lenses as actually made, am having trouble understanding how anything I can report about mine can interest anyone. Except, perhaps, for remarks about distortion seen in, e.g., the few photographs of USAF 1951 test charts I've taken.

It is often hard to get optical prescriptions for old lenses in US patents. I have examined tens of thousands of old lens patents, both for work and as a hobby, and for some older lenses the prescriptions are even hand-written on the patents!

Here's how to see your aberrations: go out somewhere dark, focus well at infinity, and take perhaps 1-3 second time exposures of star fields (depending on ASA). Best to use a 2nd magnitude star so it doesn't blow fine detail away. 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.

 

[Dan Fromm]

It is often hard to get optical prescriptions for old lenses in US patents. I have examined tens of thousands of old lens patents, both for work and as a hobby, and for some older lenses the prescriptions are even hand-written on the patents!

Thanks for the reply.

Three thoughts. First about making point spread functions visible, fine, wonderful, thanks for the hint. Who will pay for the film and processing? How will seeing them benefit my photography? Have you looked at dioptrique.info?

 

[jonesmi]

Thanks for the reply.

Three thoughts. First about making point spread functions visible, fine, wonderful, thanks for the hint. Who will pay for the film and processing? How will seeing them benefit my photography? Have you looked at dioptrique.info?

You're most welcome.
Not following your pay question.
Yes, dioptrique.info is another good historical lens site. I don't speak French, so I'll have to let Google Translate do it.

 

[Dan Fromm]

You're most welcome.
Not following your pay question.
Yes, dioptrique.info is another good historical lens site. I don't speak French, so I'll have to let Google Translate do it.

About paying. I have many lenses, and by lens I mean design type and manufacturer, e.g., f/6.3 Tessar and Zeiss, f/6.8 Beryl (Dagor clone, I don't know which version) and Boyer, and so on. Using film to find PSFs is somewhat costly these days. Before I take the pictures needed to see PSFs I'd like to know how seeing them is likely to change my practice as a photographer.

I ask this last question because I've never known what to take away from the calculated PSFs on dioptrique.

 

[RalphLambrecht]

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

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?