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04-09-2010, 04:34 PM   #1
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Need an expert in Pentax 6x7 stuff

Hello Everyone, I'm trying to do a project and research on 6x7 lenses, I've spent the last 5 days and countless hours searching for the patents on the 6x7 lenses. i've looked at patents from 1970-1994. I've looked at patents from more then 10 companies beyond Asahi. I've looked through at least 2000 lens patents and still haven't found one that seems to match.

Were Pentax (Asahi) 6x7 lenses made by another company?

All i need are patent numbers, I'm hoping that the lenses come with manuals that might quote the number on it, However if there is anyone here who could point me in the right direction when looking for the patents that would also be much appreciated.

Thanks

Michael

04-09-2010, 05:23 PM   #2
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The patents for 6x7 lenses probably predate the internet and since there would be little or no value to publishing them on the net, you are probably not going to find what you want on the net.
None of the owners manuals that I have for 6x7 lenses quote patent numbers.
All Pentax 6x7 lenses were made by (Asahi) Pentax.
You will probably need to get in touch with Pentax themselves and hope they are willing to help.
04-09-2010, 05:42 PM   #3
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QuoteOriginally posted by Wheatfield Quote
The patents for 6x7 lenses probably predate the internet and since there would be little or no value to publishing them on the net, you are probably not going to find what you want on the net.
I have found many lenses in patents from 1976 onward including the prototype for the K 20mm F1.4 that never made it to market, the most important lenses to me are newer 1980 and later.

QuoteOriginally posted by Wheatfield Quote
None of the owners manuals that I have for 6x7 lenses quote patent numbers.
Thanks

QuoteOriginally posted by Wheatfield Quote
All Pentax 6x7 lenses were made by (Asahi) Pentax.
You will probably need to get in touch with Pentax themselves and hope they are willing to help.
Patents are public records if i'm not mistaken so they should share them, its not like they hold any secrets 30+ years later
04-09-2010, 08:29 PM   #4
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QuoteOriginally posted by MightyMike Quote
I have found many lenses in patents from 1976 onward including the prototype for the K 20mm F1.4 that never made it to market, the most important lenses to me are newer 1980 and later.



Thanks



Patents are public records if i'm not mistaken so they should share them, its not like they hold any secrets 30+ years later
Being able to help and being willing are two different things...

04-10-2010, 12:03 PM   #5
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QuoteOriginally posted by Wheatfield Quote
Being able to help and being willing are two different things...
Do you have to be so logical! LOL I'll try to find a way to contact Pentax on Monday but they really don't have many options for contacting them on their website
04-10-2010, 08:33 PM   #6
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There may not be anything new on the 6x7 lenses that was patentable. Most of them would simply be scaled up versions of 35mm lenses using well tested designs. I can't find any lens diagrams so there is no way of proving it but it would be very interesting to compare the 6x7 lenses to the 35mm equivalents. If there are patents they would most likely be on the wides (35 & 55) the 90LS, 75 shift or 1000 reflex lenses.

I expect that the 6x7 mount would have a patent, maybe aspects of the shutter, the film loading system, the chain drive linking the meter and the lens aperture and there are probably other bits and pieces as well that are unique to the 6x7.
04-11-2010, 06:40 AM   #7
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There are diagrams, look to the bottom of this website there are 4 links posted with diagrams

Pentax 67 Lens Guide

they weren't just scales up, sure some have design similarities to their respective lenses in 35mm but there are more differences then just scaling up, a greater back focus distance plays a very big role in design difference.
04-11-2010, 06:11 PM   #8
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I didn't mean literally scaling it up, rather taking the designs that worked in the smaller size and translating it to the larger size. This was the way things were done prior to the introduction of SLRs that needed retro-focus wide angles and telephoto lenses. Most manufacturers had a family of maybe six designs which they would offer in a range of focal lengths.

I haven't been able to find diagrams for the screw mount lenses, but using the early K lenses on Boz's site you find that the 35 fish-eye uses the same design as the 17/4, the 75/4.5 is the same as the 35/3.5, the 300/4 is the same as the 150/4 and the 135/4 macro is the same design as the 100/4 macro.

I would have expected the 105/2.4 to be a scale up of the 50/1.4, but it is the same design as the 50/1.7 so maybe the process goes both ways. Of the 2nd generation of 6x7 lenses, the 165/2.8 is the same as the 55/1.8 and the 500/5.6 is the same as the 500/4.5. I expect that the 500/5.6 actually re-uses most, if not all, of the elements from the 500/4.5 which was available as a 6x7 lens at one point (probably special order since it doesn't appear in the catalogs).

The newer 6x7 lenses all appear to be unique designs.

04-12-2010, 07:11 AM   #9
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Maybe some of the 67 primes have designs like the Double-Gauss or similar non patentable designs due to their age.
04-12-2010, 12:48 PM   #10
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I know for sure that Pentax's 35mm lenses had US patents. P67 lenses should have them as well because even though they were using the same basic design types as their 35mm counterparts, they were unique to the 67. We know through Geometric Optics that simply scaling up a 35mm design leads to problems. Medium format designs must be better corrected than a scaled up 35mm design just to match 35mm performance. For example, a 35mm format 50mm Double Gauss design does not have a serious chromatic aberration issue, while a 105mm medium format Double Gauss design will have chromatic issues unless addressed by the designer to compensate. Not only did Pentax borrow from their 35mm design types but many companies used similar designs. The German Ernostar type has been used by Pentax but it is their own version (200mm Pentax and 165 LS). Glass types, radii of curvature of elements, element spacing etc are all proprietarty and patentable.

Attached are two Pentax zooms designed by Takayuki Itoh of the Asahi Optical Co. They both have US patents and were for 35mm SLR cameras. The current P67 zoom (55-100mm) is similar in design but not identical. The 35mm design heritage can easily be seen.
Attached Images
 
04-12-2010, 01:44 PM   #11
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Wow thanks for opening my eye to the extreme similarities but with differences, I'll keep looking and I'll try to find out more directly from Pentax where to look, i did find the Patent for the 55mm F4.0 latest version but to begine with its the 45mm F4.0 that i'm looking for. i figure i can input the curvatures, thicknesses and indexes of refraction into an optics program and start creating my adapters from there. Oh i never said why i'm making an adapter... lets let that be a surprise
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