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Leonard Evens
16-Apr-2008, 19:37
Can anyone recommend a place to look for complete technical data on various common lenses? I I have three Rodenstock lenses: Grandagon-N 75 mm 4.5 and 90 mm 6.8, Sironar-S 150 5.6, and one 300 mm Fuji lens. I can find information about the flange focal length and from that together with the focal length I can determine where the rear principal plane is. But I don't know how to find the position of the front principal plane. For example, that could be determined if one knew the separation of the principal planes. Similarly, I don't know where to find information about where the entrance and exit pupils are. I have tried google without success. I have been able to find such information for some 35 mm format lenses, but not for large format lenses.

Mark Sampson
17-Apr-2008, 04:43
Schneider's site is full of that kind of data- for their lenses. Why don't you contact Bob Salomon- his company imports Rodenstock lenses and should have, or be able to find, the data you want. Kerry Thalmann's site has some information about Fujinon lenses, perhaps you can find some leads there.

Bob Salomon
17-Apr-2008, 04:56
Leonard,

If you send us your mailing address we can mail you the brochures and the specs.

Emmanuel BIGLER
17-Apr-2008, 07:39
I am posting here a link to the Schneider archives on the German web site.
http://schneiderkreuznach.com/archiv/archiv.htm
Scans of old Schneider brochures usually give the requested technical details regarding the position of principal planes. Recent data sheet include more details e.g. MTF charts and the pupillar magnification factor. Once you have this factor you have the position of the pupils if you know where the principal planes are located.

As far as Rodenstock is concerned, real brochures are best, but in the interim, better than nothing, there is Paul Butzi's web site wth many scans of relatively recent (end 1990's ?) Rodenstock brochures.
http://www.butzi.net/rodenstock/rodenstock.htm
MTF charts and light fall-off curves are given, but unfortunately, no data on principal planes...

As far as Fuji is concerned, Kerry Thalman is hosting scans of the brochures where the principal planes & other data are given
April, 1981 brochure: http://www.thalmann.com/largeformat/apr-1981.htm

March, 1997 brochure: http://www.thalmann.com/largeformat/mar-1997.htm
For the FUjinon C series as of 1997:
http://www.thalmann.com/largeformat/c.htm
For the Fujinon Teles where principal planes float in air at fancy locations ;-)
http://www.thalmann.com/largeformat/t.htm
I dit not find any info about pupils, though.

Nathan Potter
17-Apr-2008, 08:07
Emmanuel, many thanks for the links above - I've sort of been looking for the same technical information.

Nate Potter

Leonard Evens
17-Apr-2008, 08:29
I am posting here a link to the Schneider archives on the German web site.
http://schneiderkreuznach.com/archiv/archiv.htm
Scans of old Schneider brochures usually give the requested technical details regarding the position of principal planes. Recent data sheet include more details e.g. MTF charts and the pupillar magnification factor. Once you have this factor you have the position of the pupils if you know where the principal planes are located.

As far as Rodenstock is concerned, real brochures are best, but in the interim, better than nothing, there is Paul Butzi's web site wth many scans of relatively recent (end 1990's ?) Rodenstock brochures.
http://www.butzi.net/rodenstock/rodenstock.htm
MTF charts and light fall-off curves are given, but unfortunately, no data on principal planes...

As far as Fuji is concerned, Kerry Thalman is hosting scans of the brochures where the principal planes & other data are given
April, 1981 brochure: http://www.thalmann.com/largeformat/apr-1981.htm

March, 1997 brochure: http://www.thalmann.com/largeformat/mar-1997.htm
For the FUjinon C series as of 1997:
http://www.thalmann.com/largeformat/c.htm
For the Fujinon Teles where principal planes float in air at fancy locations ;-)
http://www.thalmann.com/largeformat/t.htm
I dit not find any info about pupils, though.

Thank you Emanuel,

I don't have any Schneider lenses, but I will keep that information in mind in case I get one.

I believe I have the Rodenstock tables you refer to which I downloaded from Linos. As you say they don't include information about principal planes. They do include image circle, rear flange focal length, and rise/fall/shift capability. I've sent my address to Bob Salomon, and I hope he will be able to send me hard copy data not available on the web.

The Fujinon tables seem to be what I need for my f/8.5 300 C lens. But there is one bit I don't understand. The data for the 300C only make sense if the actual focal length is 292.4 mm. That would be the flange focal length plus the distance between the flange and the rear principal plane. Is there something I don't understand here?

I believe that for lenses of this type, the entrance and exit pupils are located in the principal planes. I can go back and check my references, but perhaps you can confirm that for me.

Emmanuel BIGLER
17-Apr-2008, 09:31
for my f/8.5 300 C lens. But there is one bit I don't understand. The data for the 300C only make sense if the actual focal length is 292.4 mm. That would be the flange focal length plus the distance between the flange and the rear principal plane. Is there something I don't understand here?

Leonard, "commercial" focal lengths are rounded ; the actual value cannot be anything but what you computed !

believe that for lenses of this type, the entrance and exit pupils are located in the principal planes. I can go back and check my references, but perhaps you can confirm that for me.

Yes, absolutely.
In symmetric lens designs, the iris is located at the centre of symmetry to avoid distorsion. Total symmetry of the lens with a central iris implies that the pupilar magnification factor is unity. This implies that the entrance and exit pupils are located in the principal planes, because the principal planes are the points where the image/object magnification is unity = +1.
OK, one may object that this magnification factor could be -1 (anti-principal and anti-nodal points), but I do not know of any photographic lens where the pupils are located on the other side with respect to the foci !!
A better and simpler way to prove the question is to plot a ray crossing the centre of the iris at the centre of symmetry. Symmetry implies that on both sides out of the lens the ray exhibit the same angle with respect to the axis (rotating the whole figure by 180 should leave everything unchanged). Plot the continuation of the exit rays inside the lens, they should cross the axis at the nodal points since the outside rays are paralleL Nodal points=principal points in air, hence we prove that both images of the iris are located in the nodal=principal planes when the iris is at the centre of symmetry and the lens built symmetrically around it. (see attached diagram)

In reality lenses like the Fuji-C are not totally symetric but very close to, hence the pupils are located very close to the principal planes. Very close means : distant from the principal planes by a very small fraction of the focal length.

In view camera lenses, only telephotos have fancy positions for principal planes and pupils. I had played the game of analyzing my 360 tele-arton here
http://www.largeformatphotography.info/forum/showthread.php?p=169156&highlight=360+tele-arton#post169156
and I'l be glad to help anybody wishing to play the same game ;)