What kind of lens has aperture scale in mm?

[erian]

I discovered a sample where aperture scale is marked in mm instead of stops. The scale starts from 6.8 and ends with 98. It is a fairly big lens. Only identifiable information is XVI1 (1 is in subscript) on the barrel.

Could this be a process lens or where this kind of scale might be useful?

[Dan Fromm]

For a time -- some time in the 1890s to early 1900s -- Carl Zeiss Jena scaled apertures in mm. See, e.g., the 1901 CZ London catalog, which has an extensive discussion. There's a link to it in the list.

XVIsub1 is very Zeissish. See the 1910 CZJ catalog p. 14, there's a link to it in the list too.

Other manufacturers have done this occasionally, for example I have some Reichert Neupolars made well after WW II with apertures scaled in mm. 50/3.5 and 100/6.3, both high performance macro lenses for use at magnifications above 1:1.

[Jim Noel]

Lenses primarily meant for technical applications often were marked in this manner. Actually it is very practical,but requires good mathematical skills capable of mental calculations.

[Mark Sawyer]

Lenses primarily meant for technical applications often were marked in this manner. Actually it is very practical,but requires good mathematical skills capable of mental calculations.

The only math skill required would be simple division, and you'd only need to be in the ballpark for practical purposes.

I've run across a few old lenses that had little marks on the aperture scale at 1 cm and 0.5 cm, or 1 inch and 0.5 inch aperture. That makes the calculations VERY simple.

[pjd]

Scales marked in mm are very useful with convertible sets, where different combinations would give different f stops wide open. I have a Zeiss Protar VII casket set with a barrel marked in mm, double Protars and Amatars often have a mm scale on the shutter alongside f stops, very useful. It's handy for bypassing bellows extension calculations too - maybe that's where it'd be useful with process lenses.

[Pere Casals]

Actually it is very practical

I guess it should be very useful to calculate the effective aperture when we give bellows draw for a close focus...

I'd ask if the aperture in mm is the real hole or if it is the effective hole size, seen from the front, to give the value that's used in the f/ calculation...

[Mark Sawyer]

...I'd ask if the aperture in mm is the real hole or if it is the effective hole size, seen from the front, to give the value that's used in the f/ calculation...

That would be the trick when using it with the casket set as mentioned by pjd. Different front cells would render slightly different sized effective apertures from the same raw aperture.

[Pere Casals]

That would be the trick when using it with the casket set as mentioned by pjd.

OK, now I understand it, thanks for explaining it.

[Mark Sawyer]

I figured you'd know it already, Pere, but some here may not. Your comment was just the perfect lead-in to my point.

[Matt Stage]

That would be the trick when using it with the casket set as mentioned by pjd. Different front cells would render slightly different sized effective apertures from the same raw aperture.

The Tri Tran Signature Pictorialist Lens is a casket system with meniscus lens elements available in focal lengths from 9" to 30". To address this issue, the aperture scale is marked in Roman numerals from I to VI.

197659

More info about this lens is ate the website: https://www.tritranphotography.com/tt-signature-lens

[Mark Sawyer]

The Tri Tran Signature Pictorialist Lens is a casket system with meniscus lens elements available in focal lengths from 9" to 30". To address this issue, the aperture scale is marked in Roman numerals from I to VI.

I think I remember reading about the Roman Pictorialists in Newhall's The History of Photography...

[Dan Fromm]

The Tri Tran Signature Pictorialist Lens is a casket system with meniscus lens elements available in focal lengths from 9" to 30". To address this issue, the aperture scale is marked in Roman numerals from I to VI.

197659

More info about this lens is ate the website: https://www.tritranphotography.com/tt-signature-lens

Silly semantics alert!

I'd always that that casket sets were a collection of cells that could be singly or in pairs as desired. Each cell is claimed to be a fully corrected anastigmat. If I understand Tri Tran's product slate correctly, all of his lenses are single element meniscii and he sells barrels in which meniscii of various focal lengths can mounted, one at a time. This doesn't seem to be quite the same as combining cells to make fully corrected double anastigmats or even switching single multi-element cells in a barre.

[Mark Sawyer]

This doesn't seem to be quite the same as combining cells to make fully corrected double anastigmats or even switching single multi-element cells in a barrel.

And that's what makes it a "Signature Pictorialist" lens! Silly photographers, always wanting well-corrected lenses... :rolleyes:

[Havoc]

I figured you'd know it already, Pere, but some here may not. Your comment was just the perfect lead-in to my point.

I didn't know and still don't understand. Could anyone of you who does please elaborate what this is about? I feel like being on the sideline of some very private joke.

[Mark Sawyer]

One of the basics of photography: the f/stop is determined by dividing the focal length by the aperture's diameter as measured through the front element, (aka "entrance pupil").

When pjd mentioned casket sets (a barrel with multiple interchangeable elements for different focal lengths) being marked in mm, and Pere asked "if the aperture in mm is the real hole or if it is the effective hole size, seen from the front, to give the value that's used in the f/ calculation", I just pointed out that different cells would render different effective aperture sizes, which Pere had said a little less directly.

The manufacturers' aperture scales always give f/stop values for infinity. For those of us who frequently work at close enough distances to need to factor in a longer focal length (bellows extension), having a scale marked in effective aperture diameter would be a more convenient way to figure exposures than converting from infinity-based f/stops.

[pjd]

I mounted a Zeiss Protar VII set and made some measurements. The mm scale on the barrel reflects the physical aperture (how could one scale compensate for different cells, if cells of differing power really make much of a difference to effective aperture). With a 48cm cell up front the aperture apparent through the front element appears less than 1mm different to the physical aperture as shown on the scale. Measuring through the front element is quite tricky, I think this is close enough to be workable.

Zeiss did distribute tables with casket sets showing the aperture in mm required for a given f stop with various combinations of cells, maybe they adjusted these slightly to account for effective aperture rather than actual mechanical aperture. I don't think fractions of a mm make enough of a difference to worry about - my exposures generally come out well enough, and when they don't it's not Carl Zeiss and their mm aperture scale to blame.

[Havoc]

The manufacturers' aperture scales always give f/stop values for infinity. For those of us who frequently work at close enough distances to need to factor in a longer focal length (bellows extension), having a scale marked in effective aperture diameter would be a more convenient way to figure exposures than converting from infinity-based f/stops.

Ok, got it. It's another way to do bellow compensations.

[Mark Sawyer]

Ok, got it. It's another way to do bellow compensations.

It's calculating your actual f/stop, not compensating for an incorrect f/stop.

[Dan Fromm]

It's calculating your actual f/stop, not compensating for an incorrect f/stop.

Surely you meant effective.

[Mark Sawyer]

Surely you meant effective.

The difference being?

I think if an f/stop is the ratio of focal length to aperture diameter as measured through the entrance pupil, that would be both the actual and the effective f/stop. But I'm willing to be educated...

[Pere Casals]

I'd like to summarize what I've learned in this thread

> Aperture used in the f/ number calculation it's not the physical hole in the iris, it's the effective aperture "seen" throught the front element side.

> Taking lenses have the f?number for infinite focus, as we give bellows extension to focus close we use a compensantion factor for the modified aperture.

> "Aperture in mm" in a repro lens allows to calculate aperture directly with using and bellows extension and the mm indicated in the aperture scale, those mm are not about the actual hole (I guess), but about the effective hole seen from the front element side. As those effective mm depends on the front glass then that scale is placed in the front casket, if we replace another front casket then we have the right readings in the scale...

[Dan Fromm]

The difference being?

I think if an f/stop is the ratio of focal length to aperture diameter as measured through the entrance pupil, that would be both the actual and the effective f/stop. But I'm willing to be educated...

At infinity, the f/stop set is the f/stop you get. At closer distances the effective f/# is larger, the effective aperture smaller, than the f/stop set. In most situations the effective f/# is so close to the f/# set but when they differ by much the difference will bite you.

effective f/# = f/# set * (1 + magnification)

This is aperture adjusted for magnification, incorporates the dread and highly confusing bellows factor that becomes important only when magnification is greater than around 0.3.

[Dan Fromm]

> "Aperture in mm" in a repro lens allows to calculate aperture directly with using and bellows extension and the mm indicated in the aperture scale, those mm are not about the actual hole (I guess), but about the effective hole seen from the front element side. As those effective mm depends on the front glass then that scale is placed in the front casket, if we replace another front casket then we have the right readings in the scale...

Papi, why guess when you can look up Zeiss' own explanation? In post #2 above I directed the OP to two CZ catalogs. See p. 17 of the 1901 CZ London catalog.

[Pere Casals]

Papi, why guess when you can look up Zeiss' own explanation? In post #2 above I directed the OP to two CZ catalogs. See p. 17 of the 1901 CZ London catalog.

I was not finding the 1910 Catalog mentioned in Post #2 , the page 14 of the 1907 explains nicely, thanks.

https://web.archive.org/web/20170123200044/http://cameraeccentric.com/html/info/zeiss_4.html

197746


In page 15 they name it Apparent Diameter, (nicer than effective diameter)

197754


True, better not guessing :)

[Dan Fromm]

I was not finding the 1910 Catalog mentioned in Post #2

Tiene que usar "the list," dodo pequenito.

[Pere Casals]

Tiene que usar "the list," dodo pequenito.

Dan, J'ai utilisé la liste, mais il y a une petite erreur, le catalogue CZ de 1910 il n'est pas en C.Eccentric, et " http://www.largeformatcameras.net/ " c'est cassé.


La liste dit: "Zeiss 1891, 1892, 1910, 1927, 1932, no date" , mais 1910 n’est pas là et il contient "1907, 1924, 1927, 1929 et 1933", seulement 1927 est correct.

https://web.archive.org/web/20170120193805/http://www.cameraeccentric.com/info.html

[Dan Fromm]

Papi, de la liste:

Zeiss Jena:

1901 Zeiss London catalog: http://books.google.com/books?id=cnkWAAAAYAAJ&dq=zeiss+unar&source=gbs_navlinks_s CZ London, really. In English. Click on the little starry wheel in the upper right corner of the screen to download as a PDF.

1910 catalog: http://cnum.cnam.fr/redir?M11192 In French. Not archived, alas.

Post-WW II: http://www.arnecroell.com/czj.pdf

[Pere Casals]

1910 catalog: http://cnum.cnam.fr/redir?M11192 In French. Not archived, alas.

Just archived: https://ia601404.us.archive.org/24/items/cnum_M11192/cnum_M11192.pdf


_________

I found a Funny document, in 1951 C.I.A. made a list with key managers at Carl Zeiss Jena : https://archive.org/details/CIA-RDP82-00457R007400430012-4/page/n1

[Ron (Netherlands)]

Papi, de la liste:

Zeiss Jena:

1901 Zeiss London catalog: http://books.google.com/books?id=cnkWAAAAYAAJ&dq=zeiss+unar&source=gbs_navlinks_s CZ London, really. In English. Click on the little starry wheel in the upper right corner of the screen to download as a PDF.

1910 catalog: http://cnum.cnam.fr/redir?M11192 In French. Not archived, alas.

Post-WW II: http://www.arnecroell.com/czj.pdf

Hi Dan, thanks for the links, however in my browser there is a starry wheel but without the option to download (therefore non of the pdf's in your listings can be downloaded). Could you insert a direct link to the 1901 pdf - like you've done with the post war II pdf?

many thanks
Ron

[Dan Fromm]

Ron, there is no easily copied direct link.

I just clicked on the link in your post, got to https://books.google.com/books?id=cnkWAAAAYAAJ&dq=zeiss+unar&source=gbs_navlinks_s, clicked on the little starry wheel in the upper right corner of the screen, the drop down dropped down and I downloaded the file.

Please try again.

[Havoc]

Hi Dan, thanks for the links, however in my browser there is a starry wheel but without the option to download (therefore non of the pdf's in your listings can be downloaded). Could you insert a direct link to the 1901 pdf - like you've done with the post war II pdf?

many thanks
Ron

If you cannot download, then it is a copyright limitation of where the book is, and where you are. Here in Belgium you can also not download pdf books from Google books. Only way is going through a foreign proxy.

[erian]

For a time -- some time in the 1890s to early 1900s -- Carl Zeiss Jena scaled apertures in mm. See, e.g., the 1901 CZ London catalog, which has an extensive discussion. There's a link to it in the list.

XVIsub1 is very Zeissish. See the 1910 CZJ catalog p. 14, there's a link to it in the list too.



It indeed was a Zeiss lens - 500mm f/4.5 Tessar. The name was under the tape that had been wrapped around the top of the barrel.