A Question for Lens Designers

[Vaughan]

Hello lens designers...

Using modern materials and moulding techniques, what sort of price/performance could be achieved with aspherical elements and some computer aided design?

I love the Intrepid camera and its success in making affordable large format equipment. I'm concerned that no new affordable lenses are being made. What kind of image quality could be produced by multi-element moulded aspherical resin lenses using modern design techniques? Shutters are another problem...

[Tin Can]

https://www.pencilofrays.com/


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Lens design

[xkaes]

Valid question, but relevance? There are so many great used cameras and lenses -- at low prices -- that there is little need for new LF cameras or lenses. There will always be a few buyers who will only purchase new gear, but their numbers dwindle every day. Why buy a new Intrepid when you can get a much more flexible, better-made, used camera for the same price? Same with lenses. If lens makers thought they could actually make money producing new lenses with current technology they would be doing it.

[Jim Jones]

I agree with xkaes. New is not necessarily best, and certainly not the most cost efficient for most people. For several decades my most often used 4x5 cameras were Graphic Views, made between 1941 and 1961. The Intrepid has one obvious advantage over these durable cameras: light weight. Graphic View cameras sell on ebay for half or less than the cost of a new Intrepid. They use metal instead of plywood where metal is more durable. Both of my Graphic Views have survived with little signs of aging: they were designed to work well and last long. The Graphic company had much experience in making good cameras. It shows.
As for lenses, perhaps the most significant advance in recent decades is improved lens coating. The single coatings that became common after 1945 had a dramatic advantage over the old uncoated lenses when bright lights couldn't be eliminated in the image area. Today's multi-coatings are much better yet. Basic optical design has perhaps less dramatic improvements. My most used 4x5 lens is a Kodak f/7.7 203mm made about 70 years ago from a design 20 years older. Now we have lenses that are sharper and much faster. Some people value those improvements, but I don't miss them. I never enlarged beyond 16x20, and rarely tried LF photography where a fairly slow lens and ISO 400 film wouldn't do.
The newest and perhaps the best equipment is rarely necessary. Perhaps every serious photographer has sometime regretted not having the right equipment to capture some special subject. It seems more practical to learn to make the best of every opportunity than to invest too much in rarely needed gear. Books are cheaper than good cameras, and internet resources diminish our need for books.

[xkaes]

Just as a follow-up, while the Graphics are "tanks", there are lots of used field cameras that are very light, very flexible, and very well made for not much moola. And most large format lens designs are so simple, and have so few elements that improvements are not really needed. For normal lenses, multi-coating is less important than using a lens hood.

[Mark J]

The problem with aspheric lenses is either cost or surface accuracy.
A spherical glass lens made somewhere like India or China might cost as little as $10, and still be quite good with a figure error of a fringe ( wavelength/2 ) on each surface.
A ground & polished glass asphere would be upwards of $200 each, at least if made in Europe, but would be quite accurate.
Hence most aspheres in photo lenses are precision moulded glass, but even 'precision' in this context means 3 or 4 fringes of surface error. They can be cheap too, but if you put more than two in any system you risk degrading the overall performance, due to the surface inaccuracies. They are cheap once you have the moulds, but the moulds cost maybe $20,000+ , so you need to produce thousands of lenses for it to be worthwhile.
Aspheric polymer lenses can be moulded and be even cheaper, they can approach the same accuracy as moulded glass, but are typically lower refractive index, which is a slight limitation. Also they change power with temperature much more than glass, so they are not used in SLR lenses ; however this wouldn't preclude their use in an LF lens, and they are usefully lighter. Oh yes, they are hard to get as smooth on a microscopic level as polished glass ( typically 2x the roughness ) so this could affect contrast in the highlights.

However I would agree with Xkaes that the need for new LF lenses is quite limited. Most LF lenses are fairly slow and are used very much stopped-down, so there isn't a benefit from having several aspheres. One is often enough to give useful benefits - fox example in the Schneider Super-Symmar XL, where the asphere allowed a much smaller rear section.

It's interesting to think about, though. There might be a good 4 or 5-element lens yet to be designed, that uses the type of 'double-asphere' at the rear that is seen on many of Sigma and Voigtlander's lens cross-sections. This sort of asphere can improve field flatness in a way that would require at least two glass elements and more weight.

[Drew Wiley]

The sky is literally the limit. Most of the aspherics made right up the highway from me - largest maker of aspherics in the world - are for ground and space telescope arrays. Others for surveillance and military applications. The performance is in an utterly different league than any kind of ordinary camera lens you can think of. Whatever you want - just bring along your NASA or NSA credit card with no limit on it. And no - if you want something in the $200 range, call Disneyland instead; but they might return your phone call if $75,000 or more is in play. I don't have any contacts there any more ever since the original owner passed away. I used to chat with him several times a week - he liked to do his own gofer errands to get out of the office, and we were a supplier to their facilities odds n ends at their prior location nearby. Among many other projects, they made the correction lenses for the Hubble Space Telescope.

The problem with hybrid lenses : combined glass and moulded acrylic elements is their different rates of expansion and contraction. I am aware of an expensive MF example, and a few LF ones; but I'd be wary of any such lens element in larger size.
Maybe Jason Lane will chime in. He's the only real optical engineer on the forum I can think of. Computerized lens design has been going on for decades now. The selection of glass types might have actually diminished due to enviro rules.

[xkaes]

if you want something in the $200 range, call Disneyland instead;.

Boy, Disney ticket prices have really dropped. Or is that their stock price?????

[Mark J]

He's the only real optical engineer on the forum I can think of...
Ha !
Check my Bio.
Been working as a lens designer since 1987, was at Carl Zeiss in 1997-98

[xkaes]

He DID qualify with "...I can think of..."

[Drew Wiley]

Thanks, Mark. Nice to know another engineer is on board. But I was specifically referring to no-limit budget options, since this thread is about hypotheticals anyway. For a price, you can get pretty much anything. Plastic aspherics are more an amateur lens thing. For awhile, I once worked side by side with a former NASA optical engineer; and how they did things in the Pioneer Satellite era compared to today would seem almost like a Stone Age comparison.
Flexible aspheric mirror arrays combined with aspheric optics, that's big now. Way way too big for my own tripod, however.

[Mark J]

Yes ! :)


......combined glass and moulded acrylic elements is their different rates of expansion and contraction. I am aware of an expensive MF example, and a few LF ones.
I noticed recently that this technology is still being used ( Sigma, Tamron ? ) . Maybe Zeiss were first to try it, the 35mm f/1.4 in the late 70's had an asphere of that sort, i believe. I bet it wasn't AR coated back then, though.
What are the MF and LF examples, I can't think of them - am interested to know.

The other definition of 'Hybrids' is a stepped phase surface machined into a lens ( like a precision fresnel with accurate 1-wavelength steps ) . I think Canon are the only company who put anything like this into production in the photo world. They are used extensively in the thermal infra-red.

[Joseph Kashi]

Ha !
Check my Bio.
Been working as a lens designer since 1987, was at Carl Zeiss in 1997-98

Hi, Mark

What are you doing now in North Wales, asks this MIT type in rural Alaska <GG>

[Mark J]

There's a company that started in 1968 as a collaboration between Pilkington Glass, and Perkin Elmer Corp. It was called PPE then and until the '90s, then became Pilkington Optronics, then Thales Optronics, then Qioptiq. I have spent most of my career here. We do Head Up Displays for aircraft , thermal IR Zoom lenses, Night vision kit, etc etc. We have the second-biggest optical design group in Europe.

[Mark J]

Going back to what the OP was asking for, bear in mind that fine colour correction ( especially lateral colour when stopped down ) is a feature of all the best LF lenses. You can't get the colour very well corrected with just resins or polymers. For instance the Symmar-S and Apo Symmar use two types of glass that are 'anomalous' ie. away from the 'normal line' on the dispersion charts. These can't be replicated by polymers, partly because the tolerances and basic data on polymers is not good enough to get reliable 'Apo' correction.
However,a combination of glass and a polymer with low power but having aspheres, could be the way to go.

Are you looking for a lightweight lens ?
What sort of spec of lens or existing example are you thinking about ?
It would be an interesting design exercise.

[Vaughan]

Thanks for all the replies, I wasn't expecting such volumes of response. Particular thanks to the "real" lens designers who contributed.

My question was partly from technical curiosity: "Using modern materials and techniques, how cheaply could a good lens be made, or how good could a cheap lens be made?"

Other than curiosity, I've been thinking about the companies that are designing and manufacturing new large format cameras, and thinking that the lack of new lenses must surely be a threat to their business, at least in the long term. Currently it's impossible for them to sell a complete, brand new large format camera that includes a lens. If they had an opportunity to, say, build and supply 1,000 new cameras to every school in the USA, they wouldn't be able to do it by relying on buying used lenses. They wouldn't even be able to provide a cost estimate because the price of lenses will start rising as they start buying them.

Like I said, just a thought.

[John Layton]

I'd like to chime in here with respect to Vaughn's observation that many new LF cameras are coming to light, and that he'd like to see a concurrent development of new LF lenses. I heartily concur with this!

My further thought is that, as many of the new LF cameras are attempting to be of the "lighter weight" variety (which my aging body certainly embraces!) - I think it would be absolutely fantastic if someone could bring to market a series of lenses, rationally stepped in focal lengths...that would also embody this "compact/lightweight" approach. Plus...they'd all share the same front diameter so only one set of filters would work for all of them!

[Mark J]

The key to making anything cheap these days is manufacture in the far East / India.
However you've still got the fixed cost of a shutter, presumeably Copal ?

Is any manufacturer still making LF lenses now ?
I know Schneider aren't ; Rodenstock moved to lenses for digital, mainly for machine-vision applications . Fuji ?

The problem for any potential lens maker today is that despite the increase in a couple of camera brands, the market is still awash with high quality secondhand lenses from the Pro LF era. You're not going to be able to make a new lens as good as a near-mint Schneider Symmar-S for less than $250.00

John's comments above, are understandable, a little ambitious perhaps ( getting common filter sizes for wide-angles is unlikely ) , but if you stand back and go through the existing options, you will remember that Fuji did almost perfectly what you're asking for, with their final 'CM-W' series. All of these lenses are available in good condition any day of the week on EBay. Having a common filter sizes does work slightly against minimum weight of course - these all had 67mm if I remember correctly.

Optics has moved on a little in the last 20 years, but not as much as you might think, it's a very mature science (/engineering) where only small increments are possible ; unlike electronics, you can't expect optics to keep shrinking down in size endlessly. You have to meet the laws of physics - eg. a 210mm f/5.6 still needs a 37.5mm hole down the middle.

I think that the main areas of improvement in recent years are glass moulded aspheres and coatings.
I think there is certainly scope to improve on simple 3, 4 or 5-element lenses for the larger formats, where the existing options are limited and prices climbing.

[Tin Can]

https://youtu.be/7sosQyHy5SQ


Water lenses

DIY

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AND Art class

[Michael R]

This may or may not still be the case but in recent years there have been periodic limited production runs of certain Rodenstock (->Linos->Qioptiq->Excelitas) analog LF models. It was/is called the “Edition” series. I guess they had/have a stash of shutters? Anyway… they are enormously expensive: https://www.linhofstudio.com/products/Analogue-Lens-Rodenstock


The key to making anything cheap these days is manufacture in the far East / India.
However you've still got the fixed cost of a shutter, presumeably Copal ?

Is any manufacturer still making LF lenses now ?
I know Schneider aren't ; Rodenstock moved to lenses for digital, mainly for machine-vision applications . Fuji ?

The problem for any potential lens maker today is that despite the increase in a couple of camera brands, the market is still awash with high quality secondhand lenses from the Pro LF era. You're not going to be able to make a new lens as good as a near-mint Schneider Symmar-S for less than $250.00

John's comments above, are understandable, a little ambitious perhaps ( getting common filter sizes for wide-angles is unlikely ) , but if you stand back and go through the existing options, you will remember that Fuji did almost perfectly what you're asking for, with their final 'CM-W' series. All of these lenses are available in good condition any day of the week on EBay. Having a common filter sizes does work slightly against minimum weight of course - these all had 67mm if I remember correctly.

Optics has moved on a little in the last 20 years, but not as much as you might think, it's a very mature science (/engineering) where only small increments are possible ; unlike electronics, you can't expect optics to keep shrinking down in size endlessly. You have to meet the laws of physics - eg. a 210mm f/5.6 still needs a 37.5mm hole down the middle.

I think that the main areas of improvement in recent years are glass moulded aspheres and coatings.
I think there is certainly scope to improve on simple 3, 4 or 5-element lenses for the larger formats, where the existing options are limited and prices climbing.

[Oren Grad]

However you've still got the fixed cost of a shutter, presumeably Copal ?

Copal shutters for LF lenses are long out of production.

[David Lindquist]

This may or may not still be the case but in recent years there have been periodic limited production runs of certain Rodenstock (->Linos->Qioptiq->Excelitas) analog LF models. It was/is called the “Edition” series. I guess they had/have a stash of shutters? Anyway… they are enormously expensive: https://www.linhofstudio.com/products/Analogue-Lens-Rodenstock

The "Edition" series consisted of five focal lengths, 150, 210, 240, 300, and 360 mm. It is my understanding that Rodenstock made up 25 of each focal length for this offering. Linhof & Studio show the 150 mm as "sold out" with the remaining four focal lengths still available (and the 210 mm is listed as "In stock"). Badger Graphic and Christoph Greiner only show the 240, 300, and 360 mm lenses on their respective websites.

Linhof's current lens price list is dated March 1, 2023. For analog lenses it shows the "Edition" series in focal lengths 210-360 mm.

David

[Mark J]

Copal shutters for LF lenses are long out of production.

I did wonder, that's a damn shame and kills off any prospect of a proper new production job as far as I can see.