Home

Please support mflenses.com if you need any graphic related work order it from us, click on above banner to order!
SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Some official specifications on >f/1 Kowa lenses
Post new topic   Reply to topic
Home   Manual Focus Lenses
View previous topic :: View next topic  


PostPosted: Fri Jan 07, 2022 5:46 pm    Post subject: Some official specifications on >f/1 Kowa lenses Reply with quote
I don't know why I didn't look on Google Scholar/Google books sooner for this stuff (fast 'X-ray'/image intensifier lenses), because it contains all the (official) answers about using this equipment you'd ever want. How to mount to multiple cameras, measured T stops of when the lenses were new, sometimes even element diagrams in setup photos. Also, many lenses whose only record of existing is probably these documents.
Exotic equipment like this is interesting, but it is also hardly ever made for enlightened purposes. Do well to remember this.

These 'specifications' were found in an advert placed for these high speed lenses, in multiple issues of Photonics Spectra. A simple search for intensifier "kowa": https://www.google.com/search?q=intensifier+%22kowa%22&biw=1366&bih=682&tbm=bks&ei=8m3YYeuiJNWChbIPs8qW4A0&ved=0ahUKEwjr46udi6D1AhVVQUEAHTOlBdw4ChDh1QMICA&uact=5&oq=intensifier+%22kowa%22&gs_lcp=Cg1nd3Mtd2l6LWJvb2tzEANQ_wFY9AVg9QZoAHAAeACAAXOIAd0EkgEDMi40mAEAoAEBwAEB&sclient=gws-wiz-books

Scans of Photonics Spectra can be found on archive.org, where you can rent them out for an hour online with a free account. The image below was found on page 6, here: https://archive.org/details/sim_photonics-spectra_1983-02_17_2/page/6/mode/2up

The advert seems to have been run as early as 1981.



Crop of just the lenses:



From this, we have the following specifications:

Kowa 42mm f0.75
11mm image diameter
'imaging lens'

Kowa 42mm f0.95
17mm image diameter
'imaging lens'

Kowa 42mm f1.1
? image diameter
'available in C-Mount'

Kowa 50mm f0.75
? image diameter
'for image intensifier or video camera'

Kowa 60mm f0.7
45mm image diameter
finite conjugate (7.78:1)

Kowa 67mm f0.95
20mm image diameter
'collimator lens'
'compact'

Kowa 77mm f1.1
20mm image diameter
'T.V. camera or collimating lens'

Kowa 90mm f0.95
22mm image diameter
'collimator lens'

Kowa 100mm f2.0
30mm image diameter
'cine lens for medical cameras'

Kowa 80-135mm f2.8
? image diameter
'for medical applications'
'Adapts for Arri, C-Mount and others'

If we're just judging it on 'who has the biggest image circle', then some of these are ahead of Delft Rayxar/Rodenstock Heligon line, or equals it.
Finite conjugate = designed for macro distances, the rest infinity objectives. Much like the Wray f1.0 'CRT' copying 4:1 lenses of the 50s (which is a Double-Gauss design that became the Unilite, nothing todo with the 'fast triplets'. Go look at the patents: US2487750A and US2499264)


To speculate (someone with more expertise please correct me): technology might have settled down by 1981 to not need it. For instance go back 15 years and you see people modifying 35mm cameras to use with these lenses regardless of the falloff, or desiring for these lens to cover 35mm. Not so much of that I can find in 1980, maybe 'electronic imaging' settled down. Also, some similar f0.75 General Electric lens patents of this age only have a 13 degree field, for instance.
Then again, post 1970 you can find talk of Rayxars now covering a 20 degree field faster than f0.7, same basic patent. Who knows!


PostPosted: Sat Jan 08, 2022 9:45 pm    Post subject: Reply with quote
These lenses are unfamiliar to me, but it's always fun to learn about fast / exotic lenses.
Thanks for the information, eggplant.

Like 1 small


PostPosted: Mon Jan 10, 2022 3:27 pm    Post subject: Reply with quote
55 wrote:
These lenses are unfamiliar to me, but it's always fun to learn about fast / exotic lenses.
Thanks for the information, eggplant.

Like 1 small


It's understandable why that unfamiliarity persists.

They are designed to work for a very narrow set of circumstances, once they've fufilled their role it's hard to think of how to sell them on for any other purpose, hence they're 'dumped' and rediscovered periodically.

This is just how it will be for a lot of industial equipment. Some more common ones become more famous (Rayxar 50mm f0.75), but are all 'dumped' the same way*; they all carry a level of unfamiliarity, obscurity.

This means that many go under the radar. I own one which has, have a few bookmarked that have. The famous ones get bought but who has a paper from 50 years ago detailing a Leitz 150mm f0.85 covering 70mm film to hand.


Anyway, as an addendum:

These Kowa lenses are given or referred to with codes, which aren't written on the lens bodies.



Kowa 75mm f/1 is Model C139B.

from Performance characteristics of a Pr‐based infrared quantum‐counter imaging system (1979)
https://aip.scitation.org/doi/10.1063/1.326395
(available on Scihub)

What we have below is 'two in one' - a model code and a diagram of the Kowa 50mm f0.75. Unfortunately, the scan is too poor for me to make out the model code. The diagrams however are just legible enough to be traced:






This had to be quick, and I looked at both to decide the shapes. It's the spitting image of the Rayxar rather than the XR Heligon- the surfaces and thickness of the second cemented component is an obvious starting point to spotting the differences.

However, the first element of that second doublet isn't as thick, and the air-space after it is larger. Up to you whether you think I've wrongly interpreted the drawings.

*This can also apply to information on these lenses, quickly disposed of


PostPosted: Tue Jan 11, 2022 7:26 am    Post subject: Reply with quote
Yep, that latter one is a cascaded two-stage image intensifier system using two KOWA lenses as a relay lens to project and adjust image size from that ultra-fast R-Biotar 120mm with its rear MCP intensifier to the rather small image size 2nd intensifier system. Guess it is about photon counting.


PostPosted: Tue Jan 11, 2022 7:31 am    Post subject: Reply with quote


Tried to make it a bit more legible...

Actually I have quite of few of them, started collecting them years ago for some experiments. SOme worked rather well as did the HELIGON ones from competing company RODENSTOCK (name back then).

Thanks for sharing!! Like 1 small Like 1 small Like 1 small
Post new topic   Reply to topic
Home   Manual Focus Lenses
Page 1 of 1