Schneider APO-SYMMAR-L 210/5.6 COPAL #1

since: 2018/03/02
update: 2018/06/03
reference:
1. Apo-Symmar "L"
2. Schneider APO-Symmar 210mm Sweet Spot?
3. Lens sweet spot
4. Beginner, Optimum Aperture
5. Is f/22 the Sweet Spot for 4x5?
6. Clarification on f11 sweet-spot
7. Test Results - Large Format photographic lenses
8. Aperture and image circle

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This is a large format photographic lens for view camera photography with film formats
up to 8x10 inch, although it's most common use is for 4x5 inch photography. It has a 75
degree angle of coverage at f22. This results in an image circle of 321mm at f22, which
allows shift of up to 101mm vertically and 93mm horizontally with 4x5 inch film. It Uses 77mm Filters(前後皆是), Schneider Apo-Symmar 210mm lenses have long been
considered the standard lens - the workhorse(主力) - for 4x5 photography.

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One well-known LF photographer--John Sexton, if remember correctly
--said that 95% of his LF photos were shot at f32. If it's good enough for him . . .

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Wide-open(廣角), lenses are typically less sharp because of incompletely
corrected aberrations(像差). As you stop down, some of the aberrations improve,
improving sharpness. But if you stop down too far, diffraction(衍射) takes over,
reducing sharpness.

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So the sharpest aperture will be somewhere in the middle. But you shouldn't necessarily
just always use the sharpest aperture. Depth of field(景深) might be more important, and
therefore you might need to stop down farther.

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In LF photography, coverage(覆蓋範圍) also comes into play. A lens might be sharpest
at the center at f11, but still quite soft in the corners. If one wanted to make a simplistic recommendation, I would say that the best apertures are around f16 to f32.

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For enlargements from a 4x5 film taken at f64, I would expect a softer result
because of the f64 aperture.

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In use, rough focus wide open, now stop down to f8.0 and refocus with a magnifier(放大鏡). You will then get the focus you wanted. There is seldom(很少) a need to stop down to f64 or smaller, you should be using your front swings(前置搖擺) to place the focus exactly where you want it before stoping down, and then stop down only the amount you need.

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Start at f22 and go from there...perhaps shoot some transparencies and try f16 and f32
on the same image for 'kicks and giggles' to see what you 'like'. I think you will find the
right balance at f22, i.e. sharp and corners, etc.

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