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giorgio.lanz
4-May-2007, 10:16
I have the possibility to bay a Carl Zaiss Jena 450 mm Apo tessar.
In some plaice in this forum I read that a apo tessar cover more o less a little bit more that the focal length , that means that the lens is good r the 8 x 10 format (that is what Iím looking for).

It is a 1936 lens.

Any suggestion/ comment about the quality of the lens?

Thanks for the Help

Uli Mayer
4-May-2007, 11:37
Neither a statement on Apo-Tessars in general nor about this particular lens. Just a quote from a Zeiss price list of the late twenties or early thirties:

Tessar 3.5/21cm............... 380,- Reichsmark
Triotar 3.5/21cm................190,- RM
Doppel-Protar 20.5cm.........220,- RM
Protar 1:18, 18cm ...............95,- RM

Apo-Tessar #1 46cm..........400,-RM
Apo-Planar #11 41cm..........800,-RM

(all prices from "Druckschrift P 265")

Arne Croell
5-May-2007, 02:03
Apo-Tessars were usually specified at 43į coverage; that would be 354mm for the 45cm/450mm one, so it covers 8x10 with some movements. This number is for process applications. As with most Tessars, the circle of illumination is larger, so you might be able to use more than the 354mm depending on your quality criteria. I you only want to do contact prints, you certainly would have a larger usable circle, but how much larger depends on what is acceptable for you.

giorgio.lanz
5-May-2007, 02:32
Thanks to all.

At Uli because it give me an idea about the scale of value (if the price means something) and to Arne because now I understand the formula to calculate the imagine circle (realy i do not find exactly 354 mm but at little less - 329,85 but probably may "Reconstruction " of the formula was not fully correct) .

Arne Croell
5-May-2007, 03:02
Thanks to all.

At Uli because it give me an idea about the scale of value (if the price means something) and to Arne because now I understand the formula to calculate the imagine circle (realy i do not find exactly 354 mm but at little less - 329,85 but probably may "Reconstruction " of the formula was not fully correct) .

The formula is:
focal length·2·tan(angle/2)=image circle
So here it is 450mm·2·tan21.5°=354mm

giorgio.lanz
5-May-2007, 03:34
Thanks Arne

I use sin and not tan but may school time is finish long long time ago.
Just a silly question . The geometrical conclusion is that if I use the lens for a distance less that infinity (for example with a bellow extension of 600 mm : infinity + 33% ) may imagine circle increase of the 33% . Is it correct or other variable must be considered ?

Giorgio

Arne Croell
5-May-2007, 03:48
Thanks Arne

I use sin and not tan but may school time is finish long long time ago.
Just a silly question . The geometrical conclusion is that if I use the lens for a distance less that infinity (for example with a bellow extension of 600 mm : infinity + 33% ) may imagine circle increase of the 33% . Is it correct or other variable must be considered ?

Giorgio

Giorgio that is correct. Instead of focal length I should have put "distance from film to lens (rear nodal point, to be exact)" into the formula which then applies not only for infinity.