Leica 28 mm lenses for rangefinder cameras, part 2

The comparison of the SX 28 and the Summaron-M 28 mm is in a sense also an analysis of two different optical worlds. The Summaron-M was designed in the period that the Leitz optical department was just experimenting with computer assisted designs. The SX 28 mm is a very recent addition to the Leica lens stable and features all modern optical characteristics, from floating elements over aspherical surfaces to special glass types. The price that has to be paid for this progress in performance is cost and size. The SX is almost two and a half times times more expensive than the Summaron-M (Euro 5700 versus Euro 2200). This lens has the style and livery of all Leitz lenses of the 1950s, including the infinity lock, which is helpful when removing the lens from the body.
The Elmarit-M by comparison is almost a bargain with a price tag of Euro 2100. It is a very compact lens and has a modern appearance. When a nostalgic look and a classical optical fingerprint are not the main criteria, the Elmarit-M 28 is the most sensible choice. The SX 28 mm is the most flexible choice and the Summaron-M is a nostalgic choice.

Below are two pictures from left to right (SX28, E28, S28)

Note the round aperture circle of the S28.

The digital route

At first there will be a comparison between the lenses attached to the MM2. This body delivers the highest image quality of all digital Leica cameras and is the best for lens comparisons. All RAW images were processed in Capture One 10 with zero adjustments.The tests were made at three distances: close up (around 1 meter), medium distance (2.8 - 3 meters and infinity (beyond 10 meters).

Summaron-M 28 mm

Definition

At f/5.6 the lens delivers a medium contrast image with high resolving power that lacks the bite and crispness of the other two lenses in this comparison. The fine textural detail and the outlines of medium sized shapes are recorded with a slight softness that the other lenses lack.
At distances between 1 and 3 meters the lens exhibits a very fine balance between definition and overall contrast.
There is quite visible vignetting and the edges are very soft with blurred subject outlines.
At f/8 the overall definition increases a bit, but not by much. The recording quality is of a high order over a large portion of the image (an area with a dimeter of about 16mm). The outer zones however are quite soft and record only the major subject outlines. The edges of the image are washed out even at this relatively small aperture: this behaviour is typical for older wide angle designs.
At f/11 there are still traces of vignetting and the edges are still fuzzy. Between f/8 and f/11 the optimum of this type of lens has been reached.
To set the performance in modern perspective one might say that the Summaron at f/5.6 is as good as the SX28 at f/1.4 or f/2, a clear indication of the optical progress during the last 20 years.
At f/22 the overall image quality drops visibly and a low contrast low definition image is the result.

Flare:

there is no flare even when shooting with bright light sources shing into the lens.
Taking pictures of black structures against a very bright background shows that the lens wide open exhibits no blurring at the edges of subject outlines.

Background/foreground unsharpness

Most pictures are made of extended objects in three-dimensional space. The lens designer should not only look at the performance in the sharpness plane, but also how the sharpness is distributed over an extended area in all three dimensions, the most important of which is the axis from foreground to background. Vintage designs are characterised by a gradual reduction of definition where smoothness of gradation is most important, resulting in soft but very recognisable outline shapes. (See my book Leica Lens saga for more details). This behaviour is often referred to as 'good bokeh'. The origin is an extended blur circle caused by spherical aberration. A skilful designer can distribute the unsharpness characteristics over the full three-dimensional space.

Elmarit-M 2.8/28 mm ASPH

Definition

At full aperture (f/2.8) the lens produces a medium to high contrast image with excellent retention of detail over the full image area. There is no vignetting and only in the extreme corners the definition drops and small details are lost. The outlines of major subject shapes are well preserved. There is no important difference between the performance at this aperture and the comparable aperture of the SX28.
At f/4 the lens is already at its optimum with very high corner to corner definition. Compared to the SX-28 there is a subtle and visual difference: the Elmarit records very fine detail with more contrast and it is easier to detect very fine detail.
At f/5.6 there is, on close inspection, a very slight improvement in crispness of the textural details, only visible when the image is enlarged to 400% on screen.
At f/8 the contrast drops and a slight veil of fuzzyness over the full image area reduces the bite of the image. As with the SX28, the apertures till f/11 are fully useable and only at f/16 the image quality drops.

Flare

At all apertures there is no flare to be discerned when taking extreme contre-jour pictures. Taking pictures of black structures against a very bright background shows that the lens wide open exhibits no blurring at the edges of subject outlines. At f/2.8 the lens has excellent rendition of detail over the entire image area, equal to that of the SX-28.

More info about the Elmarit-M 2.8/28 mm ASPH can be found in another article on this site about this lens.

Summilux-M 1.4/28 mm

Definition

f/1.4: at full aperture the depth of field is narrow and some care with focusing is required. The central part of the image (about 12 mm diameter) exhibits a medium contrast image with very fine detail crisply rendered. In the outer areas the contrast and detail rendition drops and vignetting increases, darkening the image substantially even when the camera software is set to vignetting compensation. At the corners of the image area the definition drops and even the major subject outlines are fuzzy.
At quite close distances the contrast drops and very fine detail lacks crispness of detail rendition, but all information is there to be extracted by software.
At f/2 the overall performance improves due to reduced internal reflections and the suppression of spherical aberration. The outer zones (>16 mm diameter) trail behind and do not show the fine detail that is being recorded in the center of the image. The drop of contrast and loss of crispness is however very gradual. The corners have been improved and show clear outlines.
At f/2.8 there is still to be seen a very faint vignetting in the corners. The overall contrast is medium to high with a crisp rendition of very fine detail over the full image area from center to corner.
At f/4 the outer zones are free form vignetting with an improved clarity of detail: now there is no difference between center and outer zones. Extremely fine detail is clearly and crisply resolved. At wider apertures the same textural details are visible with vaguely defined outlines.
At f/5.6 the crispness of extremely fine detail has reached an optimum and the overall image produces a very high contrast from center to edges. Between f/4 and f/5.6 the optimum performance for this type of lenses has been reached. This level of performance holds till the lens is stopped doen to f/16 where a visible increase in fuzzyness reduces the overall crispness of fine detail.
While the wider apertures deliver exemplary performance, one should be aware that only stopped down the optimum is reached. This behaviour is easily demonstrated when taking pictures handheld at speeds above 1/500 and looking at the outer zones for very small detail.
The excellent performance over a large area of the image area is also a result of the absolute plane sensor surface. This surface approaches the ideal of optical designers who assume that the image area is indeed fully plane over the whole defined image area.

Flare

At all apertures there is no flare to be discerned when taking extreme contre-jour pictures. Taking pictures of black structures against a very bright background shows that the lens wide open exhibits no blurring at the edges of subject outlines, but there is some softening in the outer areas of the image and a contrast reduction in the center area of the image. At f/2.8 the lens has excellent rendition of detail over the entire image area.
There is some spill over effect in unsharp areas with strong backlighting, but it is clear if the lens/sensor or the software interpolation is the cause of this effect. The comparison with the film emulsion results might give the answer.

Background/foreground unsharpness

At f1.4 there is a steep gradient from sharp to unsharp due to a rapidly decreasing size of the blur circle. This is a consequence of a highly turbo-charged lens. Where the Summaron at f/5.6 shows recognisable shapes, the blurring of the SX-28 at the same aperture and distance in the background produces an amalgamation of shapes, making it almost impossible to discern individual elements. From the viewpoint of perception this is not an unpleasant behaviour, because the brain is 'trained' to look at abrupt gradients and interprets it as a possible danger. There are pictures where the the bokeh effect is rather pleasing for the eye and there are also situations where the bokeh is harsh and disturbing. The unpredictable behaviour of the unsharpness rendition is one of the main reasons why I am reluctant to discuss in detail the bokeh character of a lens as there are so many variables to take care of that without a laboratory attitude and procedure the phenomenon is rather subjective and often incidental.

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Some examples all made at f/5.6 first Summaron, then Elmarit, then Summilux

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The 28 mm focal length is a very versatile lens. The foreground is a very important part as can be seen in these examples.