I'm a lens designer

[Ari]

How about a Cooke for 4x5... maybe 200mm?

And aren't you getting out of 4x5? to shoot 8x10?

[Bernice Loui]

How about some short tutorials on how to set up lens cell spacing for a range of image conjugates, where the aperture should be located for specific lens types, what gives specific lens types their out of focus personalities, modern coatings -vs- older coatings and more.

There are already SO many optics available today, it would be great to get a better understating of what really makes them different and how they work.



Bernice

[Tin Can]

+1.

[Nodda Duma]

Over on APUG I'm finalizing a 165mm f/6.3 lens for 8x10" format that fits on a Copal 1 shutter. It has zero distortion and performance looks really good.

Here is a link so you can read the narrative

http://www.apug.org/forums/forum44/1...near-lens.html

If you shoot 8x10 feel free to take a look. I kind of used that thread to talk through the design path so you get to see that.

Sometime soon I'll post about this in the lens forum...to sort of pick up the narrative here as I gauge the level of interest and work with my mechanical engineer friend to wrap the glass in metal. Obviously the greater the interest the more feasible (and the lower the cost) of actually making them.


I can design anything there's interest for (Cooke's are easy), but since I do these designs at night after the kids are in bed and I also have a full time job, I'm somewhat bandwidth-limited. But that just gives me time to see where the next interest lies.

What I will try to do for designs of interest is take you along on the journey..so you get to see what's involved in lens design. Optical design is -- no joke -- 50% experience and 50% art. In the end the layout for a good lens just looks good...like a beautiful car or how pottery is shaped on the potter's wheel. Hard to describe but I do enjoy it.


Btw..Multi-layer coatings aren't really anything special...especially for visible. The coating run doesn't cost significantly more than single-layer coatings, and in a large enough coating run the cost of a coated is not significantly more when compared to the cost of an uncoated lens.


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

Regards,
Jason

[8x10 user]

Complete with Lanthanum oxide glass?

A multicoated Cooke XVa clone for less than $500.

[Old-N-Feeble]

And aren't you getting out of 4x5? to shoot 8x10?

Undecided... mostly depends on what kind of ambulatory help I can afford plus what I can afford in equipment. It's a darned difficult choice for me. I've already sold three excellent lenses dedicated for the 8x10 kit I was piecing together because I needed the funds. Hopefully, my financial situation will improve soon.

Anyway, yeah... a 200mm Cooke for 4x5 would be interesting. Whatever designs come out of this I would like the option of using perfectly round aperture discs rather than the rough hexagonal or octagonal apertures in modern shutters.

[Nodda Duma]

There are many inexpensive lanthanum-based glass types available to choose from.

Optical design software such as Code V & Zemax allow the designer to constrain glass selection by cost if desired. Many of the lanthanums will be included for use in that sort of list.


I'll start playing w/ a 200mm Cooke

[Mark Sawyer]

Welcome, Jason! I'm looking forward to your contributions!

Regarding the choice of a Rapid Rectilinear, I think you'll be competing with a lot of old RR's available cheaply, such as this 12" f/6 Versar I bought a few days ago:

http://www.ebay.com/itm/Wollensak-No...vip=true&rt=nc

But that's no reason not to pursue your own version! My own feeling is that RR's are wonderful lenses, but occupy a grey area between lenses with strong individual signatures from their aberrations (either earlier designs where they didn't know how to eliminate the aberrations or later soft designs with aberrations deliberately designed in), and modern sharp lenses that are well-enough corrected for all aberrations that they all look the same. RR's give a conventional sharp look, but don't quite perform with the modern designs. (BTW, have you found a way to correct the RR's astigmatism?)

[Nodda Duma]

Mark: that thread evolved into a request for a wide angle design giving 80+ degrees field of view. I still have the RR, but there was more interest in the wide field. Keep reading


Shutters: When I need them I order electrical shutters from places like Melles Griot. Honestly though, for my day job all the optics I design are for digital imagers and thermal cameras, which of course have their exposure times controlled by the software/firmware.


I'm not in the business of making shutters (although I can ask my mechanical engineer), but if you look up Edmund Optics iris diaphragms you might find something to suit your need. They are manual. Put that at the aperture stop position and with some ingenuity you have a well-defined circular iris (you'd still need a shutter to stack with it).

[Corran]

Fascinating.
Will follow with interest.