I'm a lens designer

[Sal Santamaura]

Sal take the focal length you want and divide by the widest aperture diameter of the Copal 1. That will be your fastest speed possible.

So 225 / 41.6 ~= f/5.4.

With the short focal length and wide field you will have light fall-off due to cos^4 law...

Jason, thank you for helping me refine my specifications. I should have said "as numerically small as possible while fitting in a Copal 1 and also meeting all the other specifications."

I have a 360mm f/10 Fujinon A with 504mm of image circle that performs admirably. If you could design something to meet the specifications in Post #94 that does as well as my 360A, with a maximum aperture closer to its f/10 than the f/5.4 in your calculation, I'd still be very happy. And, if I'm unknowingly asking you to violate the laws of physics, or you can only meet my specifications with a fat-waisted design, I'd even be willing to "grant" more weight and a Copal 3.

[Bernice Loui]

Hello Jason,

Read that book (excellent) and The Photographic Lens by Sidney Ray. Both not enough technical information to gain further understanding of the intimate details of how this stuff works which means going into the optical text books far deeper.


There have already been an awful lot of LF optics designed and built over the years. Today, it appears the majority of LF folks are using field cameras from 6x9cm to beyond 8"x 10". For these folks they are looking for light weight and small lenses that are installed in modern (Copal or similar shutters). Other basic features appears to be greater than 80 degrees of useable image circle (there will be light fall off an it appears most are OK with it), "sharp" how ever that is defined, multi coated, exotic glass and all that stuff that has been learned as marks of excellence from publications, advertising, hear-say, internet posting and all that. This is where the 165mm lens currently being worked on could fit. Yet, there were a good sized body of LF optics made over the years that already fit these requirements quite well. It is a matter of finding one, overall condition and cost. Marketable lenses that would fit into this group would be lens like the Cooke convertible in a casket set, Dagor, Protar, and a host of others that were of modest full aperture (about f6.3 to f10) to limit their physical size making them reasonable to travel with.

Another group of LF folks is involved with selective focus better known as soft focus or Pictorialism. There was a time not too long ago when soft focus lenses where worth scrap (IMO due to the group f64 movement). Lenses like the Kodak Portrait Ektar in shutter sold for no more than $50 USD and they were purchased re-using the Ilex# 5 shutter and the lens element tossed in the trash. Today, these Kodak Portrait Ektars have gone up in value by no less than a factor of 10X or more as this style of image making has returned in various degrees. Due to the limited number of surviving soft focus lenses some of which date back to before 1900, some have become extremely valuable monetary wise due to their rarity. Reproduction of oft focus lenses like the Pinkham Smith Visual Quality lens (current Cooke PS945), Veritar, Kodak Portrait, Busch Nicola Perched, Imagon, Universal Heliar, Cooke Portrait (with the knuckle) These and others have become desirable and marketable. I do have an opinion about how these lensed are to be used, they should be used with a film format no smaller than 5x7, ideally prints are contact printed, lenses should have a working aperture of f5 to f8 and of longer than normal format focal length. All this means BIG lenses, it also means BIG shutters and shutters larger than the coveted Copal# 3. Speciality lenses with a following and a real need.

There speed seekers who are looking for large aperture LF optics of f3 and larger for any given focal length. Most these are of a double Gauss formulation like Planar, Xenotar, Kodak Aero Ektar and others. Some of these LF optics have become coveted like the Zeiss Planar, Schneider Xenotar (IMO cult lens). There is a place for LF lenses like this, they are a specialty and will be physically large due to their large aperture limiting their specifications if they are to be used in the desirable Copal# 3 shutter.

Modern LF wide angle lenses have done well enough with introduction of the Schneider Symmar XL. It has been a very reasonable trade off of view angle, image circle, performance and size. Others like the Grandagon, Super Angulon, SW Nikkor does very well too except the most common complaint, they are TOO BIG.

In recent years Ultra Large Format has returned with alternative process print making via contact prints . This has increased the demand for long focal length lenses with 80 degrees or more of usable image circle. Historic lenses like 19" Dagor, 30" or longer process lenses and others are what this group seeks. Problem and limitation again is the desirable Copal# 3 shutter.


Then there are the collectors that collect rarities and all that.

In most all cases, out of focus rendition aka Bokhen matters. This means correction of aberrations and using an iris that is round, not an iris with 5-7 blades common to many modern shutters. Color rendition appears to matter much less these days due to the slow and dying off LF color film availability and processing. Contrast and flare, these are an aspect of lens personality that is often fitted to the end image maker.

This is much the summary of the current state of LF optics, what has been done, what the market might need and what is desirable. Me, I'm quite content with the set of Kodak Ektars, Goerz Dagors & Artars, modern wide angle lenses and soft focus lenses. Most are used with a Sinar shutter to remove the problem of between the lens shutters that IMO is too limiting in many ways.


Bernice

Oh and you should read "The History of the Photographic Lens" by Rudolph Kingslake if you haven't yet.

Regards,
Jason

[angusparker]

Perhaps it would be worth coming up with a list of different lenses with criteria like, FL, Max Aperture, Shutter Size, Weight, Filter Size, Image Circle at F22, Price range and using the forum poll function to let the community vote on the option they would likely buy. It might narrow down the universe of possibilities. If production runs are around 100 lenses I suspect there are a number of lenses that might have a market.

[Old-N-Feeble]

I'd be extremely interested in coated clones of the Portrait Ektar in 135mm, 200mm, 300mm and 450mm focal lengths. These are easy to design (for you anyway) and relatively cheap to manufacture compared to more complicated designs. I'd prefer they fit in old Ilex shutters because I like the nice round apertures. I'd rather not deal with slip-on apertures like the Imagons use but that would be okay too. I like the OOF renderings of the Portrait Ektar and Imagon lenses but I don't much care for single-element meniscus lenses.

[StoneNYC]

Sort of part of what Bernice said.

A question.

Is there a way to replace the aperture blades in a modern copal shutter and replace them with more blades to create a more circular Bokah pattern?

[goamules]

This talk is good. But it's still just dreaming, as is the recent Collodion B'stds Facebook planning to make a "new Petzval 8x10 lens." There, everyone discussed the focal length, speed, and barrel materials, and came up with a pretty good consensus. Which is a very difficult thing to do. And why design is fun, it's all just an exercise unless the item can be manufactured at a price the market will bear. Like Dan researched, and a lot of us know, it's easy to get a 50 or 150 year old lens, made by a company that specialized in their mass production, for just a couple hundred dollars. With the Petzval project (which no one here mentioned), the driving goal was to make a Dallmeyer 3B clone, but get this, cheaper than the originals sell for. That might be possible, it's the highest priced cult Petzval out there. But it's pretty easy to buy a vintage other petzval, probably a lot cheaper than a new one can be made.

Is there a market? Would there be buyers for 5, 25, 300 new lenses? I guess I think in traditional ways about business startups, where you create a great product, THEN if you're lucky, the buyers come. With Kickstarter, you finance the endeavor up front, with a lot of dreamers willing to throw $20 or $50 into the wind. Kind of like handing a twenty to the homeless person at the light, it makes you feel good, and you don't care what happens with the money.

So, will building a lens that isn't available now going to be useful to more than a handful of Kickstarter backers? What if it's more expensive than comparable vintage ones? Does it matter? Lomo was extremely successful with their small "petzval" that really isn't. Are they in fulltime production now? Did the people that paid $500 or whatever they ended up costing happy they didn't just buy an antique one? Rhetorical questions.....

[Nodda Duma]

Jac, multiplying elements' radii, thicknesses, and diameters, and intercell spaces by a constant multiplies focal length by the constant.

To add..the aberration values will scale up as does the weight (weight increases as volume).

So increasing the focal length by 10x enlarges a 10um blur size to 100um.

[Dan Fromm]

And volume scales with the cube ...

[hoffner]

Just a thought - where will you get new Copal shutters needed for the lenses? A Kickstarter project for them will precede the lens Kickstarter?

[jb7]

Hello and welcome-

I look forward to your input here, and will be following this discussion with interest-

This forum (and others like it) may be useful as a tool for market research, but ultimately you're just going to have to make a call, and go for it. The responses that are made on forums account for a tiny proportion of the potential market; there are many more who don't engage with social media at all.

I think your work on a wide angle 8x10 lens is admirable, though just a little more room for movements might make it a lot more attractive-
in particular, for the contact printers, a gradual falloff in resolution while avoiding mechanical vignetting would perhaps be useful.

Precision machining the barrels for use in a copal 1 sounds like it could be expensive for small runs, no?

Since you're here, there's something I've been thinking about recently-
What would be your opinion on the optically clear casting resins?

I know there would be problems; distortion of the thicker elements during cooling might be the most major one, and finding resins of different and consistent refractive indices might prove difficult. However, tooling and production would be a lot less expensive, leading to the potential for a broader range of designs.

I know nothing about these things, just wondering aloud. There will be many who will expect their lenses to be made of glass, and will not consider an alternative. Glass is more robust, of course, but is there any other reason why optically clear castable resins should not be considered?

Look forward to following your progress-

joseph