What kind of lens has aperture scale in mm?

[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/20170123...o/zeiss_4.html




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




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/20170120....com/info.html

[Dan Fromm]

Papi, de la liste:

Zeiss Jena:

1901 Zeiss London catalog: http://books.google.com/books?id=cnk...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/i...num_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-RDP8...0012-4/page/n1

[Ron (Netherlands)]

Papi, de la liste:

Zeiss Jena:

1901 Zeiss London catalog: http://books.google.com/books?id=cnk...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=cn...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.