lens that can take advantage of hi resolution films like CMS20

[Dan Fromm]

Can a lens be scaled up, retaining the proportions to the same resolution? I really do not know, and having wrestled with the issues of down-scaling aircraft as a young man I usually question intuition. I disassembled a Pacific Optical 3" Biogon and found it had fewer elements than the 38mm. (I've no idea whatsoever of the PO's resolution. Never even tried to look it up.)

Thanks for the great article!

No. Everything scales with size, including aberrations. When a prescription is scaled up, resolution attainable given aperture falls.

About the Pacific Optical "Biogon." USAF bought at least two different 3"/4.5 lenses from Pacific Optical, identified in my USAF data sheets as Paxar (A) and Paxar (B).

If I'm reading the cross-sections correctly, (A) has 8 elements in 5 groups. AWAR on Plus X Aerecon with a 1000:1 target and a W-12 filter is 31 lp/mm @ f/4.5

(B) has 9 elements in 5 groups. AWAR on AWAR on Plus X Aerecon with a 1000:1 target and no filter mentioned is 52 lp/mm @ f/4.5. On S.O. 243, same conditions, 121 lp/mm

The 38/4.5 Biogon as fitted to Hasselblad SWx cameras and to some aerial cameras (mine came from an AGI F135) have 8 elements in 5 groups.

[Drew Wiley]

You're only as good as your weakest link. Your filmholder itself will not hold the film flat enough to worry about this kind of thing. So unless you are talking about
glass plates in a lab environment or some kind of precision vacuum film back, you're barking up the wrong tree. True microfilm has been cut in 4x5 sheets from time to time, but it's rather wretched stuff for normal pictorial work. There are certain graphics arts uses. What is your application for wanting this kind of film?
Also remember that lenses designed for things like mapping are not necessarily going to deliver that kind of performance when normal view camera tilts, swings,
and offsets are involved.

[Andy Eads]

Sharpness is a relative thing. Strictly speaking, it is the sum of all the links in the chain as has been mentioned. It is also partly psycho-physical in that we will perceive as sharper an image with greater contrast when viewing two photos of equal optical resolution. With all the laws of physics conspiring against a sharp photo, it's a miracle we get anything that looks good at all. Searching for great sharpness is a fine goal if you are trying to limit the size of the beastly camera you carry. For me, there are simple limits to how far I will carry the search. If it is interfering with the story I'm trying to tell, the quest for ultra sharpness is a distraction.

[Drew Wiley]

Astrophotographers, the military, and survelliance agencies are decades ahead of us when it comes to this game. There are also forensic and art history usages for special documentation films. Going out and taking pictures and wanting sharp results - heck, that's pretty hard NOT to achieve using any number of modern lenses and large format films. Just how big a print does someone want, anyway? The problems associated with depth of field and diffraction will qualify this horse race every time. But sheer area of sheet film generally wins. I wouldn't even want CMS20 in a 35mm camera - too many micro-zits, tonality issues. But what the heck.
Tech Pan was once cut even in 8x10 sheets. I still use this for pan lith masking in color printing. But for actual pictures? - you gotta be kidding.

[Jac@stafford.net]

No. Everything scales with size, including aberrations. When a prescription is scaled up, resolution attainable given aperture falls. [... snip helpful stuff ...]

Thank you very much for the information, Dan. I was hoping you would answer.

The model B has larger elements than the Zeiss 75mm Biogon. In fact the rear element is larger than the recess on the 4" side of a Sinar 4x5 back. As you may know, many (wow, too many) years ago I bought a lot of these as military surplus, cheap. Of the whole lot, only two were pristine. The rest sit on a back shelf in Tupperware boxes, one of them in many pieces. Maybe I can burn ants with the parts.

The Paxar (Pacific Optical 3") is not worth using on LF despite being inexpensive. They were designed for 5" roll film to be used at infinity. I spent, some would say wasted a lot of time making a camera for a B model. It is sharp wide open, as is expected of aerial recon/mapping lenses, but after borrowing a 75mm Biogon for the Technika, I could find only one advantage - slightly greater coverage due to the larger size of the rear lens cluster.

Current project is to noodle out a couple different electric leaf-type shutters for Metrogon ~152mm lenses ($25 each then.)

[koraks]

Astrophotographers, the military, and survelliance agencies are decades ahead of us when it comes to this game.

And, most notably, the photolithography industry. If you're looking for extreme resolution, you might want to start taking apart some decommissioned lithography tools. Which, of course, is a purely hypothetical thing. Anyone with a basic knowledge of this technology knows it would be horribly impractical for pictorial purposes even in a very well-equipped lab setting.

[Nathan Potter]

Thanks for the nice summary Emmanuel. During the 1960s and into the 70s I made use of a couple of types of Ultra Micro Nikkor reproduction lenses for mask making on Kodak High Resolution Glass Plates. Those glass plate were rated at about 2000 lp/mm capability. The Nikkors could achieve (as listed) some 800 lp/mm resolving power using the mercury 365 nm line. But the setup had to be rigged using a high precision optical bench on a vibration isolated table. The image size was limited to about 1 X 1 cm. or less. Those early Ultra Micro Nikkors have evolved into current stepper lenses now requiring deep UV light sources (even 190 nm laser sources). These lenses are still all small field (1 X 1 cm. or so) and designed for 4X to 10X demagnification ratios and are used by stepping a chrome on glass plate image across a silicon wafer and into deep UV sensitized photoresist, not silver emulsions. Current costs are in the $500K to $5 million range for the imaging lenses. All require narrow monochromatic light sources to achieve the nominal 1000 lp/mm resolution.

As far as I know there are no lenses that can deliver 800 lp/mm using a white light spectrum. Such performance can only be achieved using monochromatic light of narrow bandwidth.

Nate Potter, Austin TX.

[Dan Fromm]

The Paxar (Pacific Optical 3") is not worth using on LF despite being inexpensive. They were designed for 5" roll film to be used at infinity. I spent, some would say wasted a lot of time making a camera for a B model. It is sharp wide open, as is expected of aerial recon/mapping lenses, but after borrowing a 75mm Biogon for the Technika, I could find only one advantage - slightly greater coverage due to the larger size of the rear lens cluster.

JAC, those monstrosities make sense for people who need what they can do. Even with the cost of putting it in shutter one can cost less than the equivalent Zeiss-made 75/4.5 Biogon, an equally specialized lens.

Steve Grimes rated the PO lenses high enough to buy what he thought were the last three pallets of them. They were in beautiful condition and he was ideally situated to put them in shutters so visions of fortunes danced through his head. And then C&H popped up with more of the same.

[jp]

Maybe wet plate is where the action is at for pictorial high res stuff. It's UV (shorter wavelength) and does not have grain as it's liquid silver, not crystalised silver.

[Jac@stafford.net]

JAC, those monstrosities make sense for people who need what they can do. Even with the cost of putting it in shutter one can cost less than the equivalent Zeiss-made 75/4.5 Biogon, an equally specialized lens.

True. I forgot how expensive the Zeiss 75/4 is. Here is a PO in an Alphax #5 shutter. With 20/20 hindsight it appears it could have been machined to take a smaller shutter. Both my #5 shutters have broken.