Angulon (not the Super one) 210mm f 6,8

[Thierry Schreiner]

Dear all,

I hope someone out there can help me. I have a Schneider Kreuznach 210mm Angulon mounted in a Copal 3 shutter, but do not have the adequate diaphragm scale.

Could those of you, who have a lens like this help me by measuring the dimensions of the apertures at the different diaphragm settings (6,8-8-11-16-22-32-45) and let me know?

Steve Grimes is the obvious answer to this issue, but as I am a bit under time pressure, I need to know asap.

One more question, please. Would this lens cover 14x17?

Thank you in advance for your contribution. I appreciate.

Best regards from France

Thierry

[Ole Tjugen]

I'm away from home and lenses right now, but if noone has answered in a week I'll measure mine.

The lens was designed to cover 24x30cm, or about 9.5x12". It can be stretched (pre-WWII models) to be said to cover 30x40cm (12x16") at f:45, but by then the corners are getting visibly soft. Later (coated) lenses have a sharper transition from sharp image circle to unacceptably soft, so are even worse outside the design limits. So my answer is: No, it won't cover 14x17". Even 11x14" is a "maybe".

[Joe Smigiel]

Well, I have one in a Compound shutter but can't seem to put my hands on it at the moment.

However, couldn't you just measure the diameter of the lens wide open and use the formula focal length/f#=diameter and go from there? For example 210mm/6.8= 30.88 mm. If you measure the lens wide open and you can verify the opening is ~31mm, then you can calculate the other aperture diameters by plugging in the other f numbers (e.g., 210mm/8= 26.25mm, etc.,).

[Arne Croell]

The Angulon is one of the lenses (many are, but not all) where the mount also defines the max. aperture. So if you have yours in the Copal and close the aperture with the shutter open, the position where the blades just become visible is f/6.8.

[Thierry Schreiner]

Dear all,

Thank you very much for your efforts.

My problem is not yet solved. As suggested by Joe, the formula focal length / f = diameter does not seem to work.

According to the formula, the opening should be +- 31mm. But the diameter of the 2 lenses facing the shutter is only 27mm. ( which would suggest an inital opening of 7,7 instead of 6,8 )

Arne's suggestion is excellent, but the lens is not mounted in the original shutter, so that doesn' t seem to help me either.

So I am still hoping someone (Ole, I'm leaning on you) has a lens available to measure the opening of the different diaphragm settings.

Best regards

Thierry

[Ole Tjugen]

According to the formula, the opening should be +- 31mm. But the diameter of the 2 lenses facing the shutter is only 27mm. ( which would suggest an inital opening of 7,7 instead of 6,8 )

That's because the glass in the front cell works as a magnifying glass. The entrance pupil is larger than the physical aperture opening, and it's the entrance pupil that must be measured and used in the formula.

However you can assume that the full 27mm diameter (inside) corresponds to f:6.8, and calculate the other openings from that. I know that max aperture is reached with the aperture blades just touching the diameter of the inner lens in the front call - it's the same for all my Angulons (90mm pre- and postwar, 120mm, 165mm and 210mm).

So I am still hoping someone (Ole, I'm leaning on you) has a lens available to measure the opening of the different diaphragm settings.

I'll be starrting on my way home in a few hours, and will get you the measurements tomorrow.

[Ole Tjugen]

Addendum:

When the Angulons went out of production, the Compound shutters were still used for all sizes larger than #2 (or is that #1? I have a Compur #2, but no compound in that size). So a Copal shutter could never be the original shutter for an Angulon.

[Arne Croell]

Arne's suggestion is excellent, but the lens is not mounted in the original shutter, so that doesn' t seem to help me either.Thierry

It does not matter at all that its not the original shutter (as long as the cell spacing is correct). As Ole explained above, its the cell mount of the inner lens that defines the maximum opening for the Angulon - when the aperture blades just have that diameter, i.e. just start to be visible, that position is f/6.8.

[Ole Tjugen]

At f:6.8 the aperture blades are just touching the visible opening. At f:8, the opening is 22mm as near as I can determine. Then for each stop divide that diameter by the square root of 2.

[Emmanuel BIGLER]

A bi-lingual answer
Following the good advice of maximum aperture given above, namely that 6.8= max aperture, you can double-check and measure the diameter of the entrance pupil by placing a small flashlight like a maglite® in the focal plane (easy by taking thr ground glass off after focusing to infinity) and see how the rays illuminate a paper placed in front of the lens. The illuminated circle diameter will be identical to the entrance pupil diameter.

Suivez les bons conseils ci-dessus en particulier l'idée que 6,8 = ouverture max ; vous pouvez mesurer vous-même le diamètre de pupille d'entrée en plaçant une petite lampe dont l'ampoule est de faible dimensions comme une maglite® dans le plan focal (c'est facile en enlevant le dépoli juste après avoir mis au point sur l'infini) et en regardant par devant sur un papier la trace du faisceau. Le diamètre illuminé est égal au diamètre de pupille d'entrée.