28 mm lenses, film emulsions, part 3.2
SX 28 mm
At 1.4 the definition in the center is excellent, with well rendered very fine detail and a low to medium contrast. The edge definition is very good with fine detail and a low to medium contrast. The corner is blurred with low contrast. There is visible vignetting that can be partly compensated in the darkroom. The overall image is quite clean but there is a very faint unsharpness over the whole negative area: the effect of residual spherical aberration.
At 2.0 the center improves visibly with very fine detail now crisply rendered with medium to high contrast. The vignetting is still visible and the outer zones do not improve as much as the center does.
At 2.8 the definition is outstanding with very fine detail crisply rendered with medium to high contrast. The edges are improved too and the corner now shows coarse detail with medium contrast.
From 4 to 5.6 the overall image improves gradually and over a large area very fine detail is rendered with medium to high contrast. At 8.0 the optimum is reached with microscopically fine detail rendered with high contrast. At 11 and 16 there is a slight drop in contrast, but less than standard knowledge would have it: diffraction does not yet deteriorate the image quality.
Elmarit 28 mm
At 2.8 the center definition is already outstandingly good: very fine detail is rendered with medium to high contrast. The edge shows fine detail with medium contrast and the corner is blurred with low contrast. There is no vignetting of significance.
At 4 the overall image improves with very fine detail at high contrast in the center and a slight reduction in contrast at the edges. The corners show coarse detail.
At 5.6 the center definition is outstanding with microscopically fine detail at high contrast and extremely fine detail over a large part of the image area. The corners now show fine detail with medium contrast.
At 8 and 11 the contrast drops and the overall quality is a bit lower, but not enough to be problematic at normal printing sizes.
Summaron 28 mm
At 5.6 the overall quality is excellent with very fine detail rendered and low to medium contrast. The corners are blurred and there is some visible vignetting.
At 8 and 11 the quality is outstandingly good with very fine detail over a large part of the image area with medium contrast.
At 16 and 22 the contrast drops and the definition of fine detail is the best the lens can give.
From the three lenses the Elmarit is the best choice.
There are two important observations to make:
The flatness of the film is excellent and there is no influence that the flatness of the emulsion does influence the performance of the lens.
The second observation is most intriguing. The very fine details have in reality a certain depth and this impression of three-dimensionality (always a hallmark of Leica lenses) is most pronounced when using film emulsions. There is a logical explanation. The objects in real space can be sliced by a number of planes that are located close to each other and at a row. In theory a lens can only record one such plane, depending on the focus choice. All other planes are more or less degraded and the role of the depth of field is to reduce this effect. A film emulsion has also a certain depth (the emulsion layer has a thickness of 135 microns or more) and the lens will project the object planes in the emulsion where the depth takes care of the location. A digital sensor has no depth and the projection is not in separate layers in succession, but as an overlay, reducing the impression of three-dimensionality.
Leica lenses, even the most modern ones, show their best character when used on a camera loaded with emulsion.