Schneider - Kreuznack Symmar-s 5.6/210

[bobwysiwyg]

I did do a search, but could not find the answer. I have the above lens and now that I have a board for it, would like to start using it. The 'marked' f-stops run from 5.6 to 45, however the pointer moves beyond 45 to a smaller f-stop. For the purposes of determining exposure, what would this last, smaller f-stop be?

[Joanna Carter]

I did do a search, but could not find the answer. I have the above lens and now that I have a board for it, would like to start using it. The 'marked' f-stops run from 5.6 to 45, however the pointer moves beyond 45 to a smaller f-stop. For the purposes of determining exposure, what would this last, smaller f-stop be?
The simple answer is that, if there is no marking it would be "slightly smaller than f/45".

All shutters need a little bit of tolerance on the movement of the aperture lever, then the position of the scale can be adjusted to calibrate the exact aperture for the marked values.

[bobwysiwyg]

I don't mean to sound flippant, but I'm pretty new to LF, but my meter doesn't recognize 'slightly smaller.' In looking at the rear of the lens while moving the f-stop lever, the difference between iris opening at f-45 (last marked) and where the lever actually stops is significant. So would I just use f-64 for the purposes of exposure?

[Joanna Carter]

I don't mean to sound flippant, but I'm pretty new to LF, but my meter doesn't recognize 'slightly smaller.' In looking at the rear of the lens while moving the f-stop lever, the difference between iris opening at f-45 (last marked) and where the lever actually stops is significant. So would I just use f-64 for the purposes of exposure?
That has to be a matter of personal judgement. If it isn't marked, then it would be something you would have to work out for yourself, based on the fact that the aperture at f/64 should be 210mm/64 = 3.28125mm.

If you fancy going to the effort of taking off the lens elements and using a tapered stick and vernier calipers to detemine what the actual aperture diameters is, only then will you be able to rely on the exposures you would get.

Bear in mind that most lenses tend to be optimised for sharpness at two stop larger than the smallest marked aperture, closing down the aperture too far will start to give you edge diffraction, which will soften your image a bit.

[Jan Pedersen]

A couple of test shots will tell you how close you are to f64. Meter a scene as acurate as you can and expose a sheet at f45 and coresponding shutter speed. Then move the apperture to what you think is f64 and take another shot with half the shutter speed as the previous shot. develope the two sheets toghether and you will soon know if the last shot was under or over exposed.
Roughly you can also measure the distance you move the slider from f32 to f45, the distance to f64 from f45 will be less. This is only a rough estimate but will get you in the ballpark.

[bobwysiwyg]

Thanks for reminding me of the ratio measurement, I should have thought of that myself. :o I just removed the rear element and transferred a 3mm measurement to a slip of paper and held it over the iris opening. It's actually less than 3mm so I guess some experimenting with exposure is in order.

[Peter K]

That has to be a matter of personal judgement. If it isn't marked, then it would be something you would have to work out for yourself, based on the fact that the aperture at f/64 should be 210mm/64 = 3.28125mm.

If you fancy going to the effort of taking off the lens elements and using a tapered stick and vernier calipers to detemine what the actual aperture diameters is, only then will you be able to rely on the exposures you would get.
The f-stop is not the diameter of the iris-diapragm but the - projected - diameter of the diaphram in the plane of the entrance pupil.

Here (http://www.largeformatphotography.info/forum/showthread.php?t=32332) Emmanuel BIGLER shows a simple way to align the aperture-scale.

Peter

[Drew Wiley]

With this lens and 4x5 film, anything f/45 or smaller is going to have serious degradation issues from diffraction. You might want to experiment, but Schneider obviously considered anything smaller than its marked f-stops as having little conventional value. When I had one of these exact lenses, and used it for years,
I don't think I ever shot it below f/32. I'm not trying to tell how how to visualize things,
but only why manufacturers label lenses the way they do.

[bobwysiwyg]

Thanks for the input all. Drew, particular thanks for the reference to de-fraction. I recall reading some posts about this. So much to learn and remember. :(

[Joanna Carter]

The f-stop is not the diameter of the iris-diapragm but the - projected - diameter of the diaphram in the plane of the entrance pupil.

Here (http://www.largeformatphotography.info/forum/showthread.php?t=32332) Emmanuel BIGLER shows a simple way to align the aperture-scale.
Thank you Peter, I hadn't realised that. You can always trust Emmanuel to know these things :)

[Arne Croell]

Roughly you can also measure the distance you move the slider from f32 to f45, the distance to f64 from f45 will be less. This is only a rough estimate but will get you in the ballpark.
Actually thats true only for older shutters like the Synchro-Compur that used circular aperture blades. Since this is a Symmar-S, not a Symmar, I assume the shutter is similar to a modern Copal or Compur (or Prontor), where the distance on the scale is evenly spaced between apertures. Its easy to see, if the other markings from f/5.6 on down are evenly spaced then f/64 is the same distance further down (not taking into account any increased tolerances at the end of the aperture lever movement)

[Jan Pedersen]

Arne, Thanks for the correction, good that some are awake when they write here.
I use mostly older shutters and never thought about the evenly spaced f stop distance on Copal shutters.