Vignetting
In the days of AgX photography the property of the lens to illuminate the negative area evenly into the far corners (the absence of light fall off or vignetting) was an important parameter. It was a bit overvalued as a slight darkening of the edges hardly bothered the subjective quality of the image and in many cases was even an integral part of the scene composition. With digital files as the basis of imaging it is easy to calculate the amount of vignetting and to correct this in the post-processing stage. Leica has this information and uses it to suppress the amount of vignetting. In order to evaluate the effects, I made a number of pictures with the SX35 and SX35FLE wide open and with the lens detection on and off. The conclusion is evident: both lenses have the same amount of vignetting, which is not surprising and the effect of the lens correction in post processing is visible too.
You can see a slight change in color correction of the JPG files too in the AUTO-mode of the camera.
SX35 FLE in OFF
SX35 in OFF
SX35 FLE in AUTO
SX35 in AUTO
Focus shift
Some time ago the topic of bokeh became a hype and you could not discuss the behavior of a lens without mentioning or demonstrating the effects of this phenomenon. In recent times the interest in bokeh is less great, but there now software programs where you can emulate bokeh or even introduce the effect where there is none in the image.
Another topic that has generated much discussion is the phenomenon of focus shift. In all lenses where the spherical aberration is still present (and that is the case in almost every lens) the plane of sharp focus wanders when the lens is stopped down. The total length of this shift can be calculated and the axial positions of the focus plane can be established too for every aperture. You can now decide to select the best focus for the maximum aperture and let the plane drift when stopping down. Or you can select a position between the two extremes to minimize the drift. This option has been used with good effect in the Nokton 1.1/50mm. Leica uses a different solution and here too the effect is clearly seen in the positive sense of course.
The focus shift of the old Sx35 ASPH has been discussed in the internet discussion groups and websites. As usual with any complicated phenomenon both extremes exist: there are some persons who have never detected the focus shift and there are some who declare that the effect in the SX35 is dramatically large. Without visual proofs or measurements made in the lab this last statement has no value. That you do not see a certain effect is no proof that it does not exist, but it is a sign that the effect might be too small to detect in normal photography. To give some foundation for the debate I have selected a series of pictures from the ranges I have made to study the focus shift of both SX lenses. A have selected the pictures that are made with the lens in the position where it is when you focus with the rangefinder. This is the 0-position in the range of pictures from -5 to +5 that I made. When you stop down you do not change the lens focus, so the location stays the same. To emulate this effect I used the 0-position for bot lenses at maximum aperture and at f/2.8. If you stop down to smaller apertures the focus shift increases but is compensated by the larger depth of field and the overall effect is minimized. At f/2.8 the depth of field is still small enough to see the effect. The pictures below are the original DNG files without any post processing, the true raw negatives so to speak. When you use sharpening the result will be different, but as noted in the X1 review a comparison is most meaningful when you reduce the number of factors that can influence the result or effect. The pictures you see are very small parts of the full image and are reproduced at 100%.
As you can see, the quality differences are small and only visible after very critical scrutiny. I also added the picture of the SX35 with best quality wide open and again you see small differences in contrast and definition of very fine detail. The conversion from DNG to web-based JPG also reduces the visible differences.
An important restriction is the limit of resolution of the M9 sensor so the best way to look at the examples is to find the reduction in contrast.
The conclusion then is that the focus shift in the two SX 35 lenses is measurable with appropriate equipment and is reduced in the FLE version. It is an overstatement to designate the effect as ‘dramatical’. You can of course try to emphasize the effect by force, but that is not the goal of this exercise.
Below SX 35 at 1.4, and SX 35 at 2.8
Below SX35 FLE at 1.4,and SX35 FLE at 2.8
Below SX 35 at best focus
Closing words
Finally I would like to ask attention for the fact that most modern Leica-M lenses (those designs that have been designed starting with the Kölsch era) provide excellent image quality. In many cases they are much better than what the photographer in the field can use, certainly with the M8 and M9 sensor limits of resolution. Reviews of Leica lenses are becoming a bit boring so to speak as the general quality (contrast, definition of fine detail and so on) at all apertures and distances is so good that you really have to search for meaningful differences. Improvement could be created in the one field where the Leica lenses are a bit weak: that is the performance in the zonal area at an image height from 14mm to 18mm and beyond 20mm image height.
The consistent high quality of the modern Leica-M lenses may the cause of the fact that most discussions about Leica lenses are drifting to extreme and often mythical, if not mystical proportions. The facts on the ground however do not support these extremes. The new SX35FLE also shows that Leica now can claim that they are able to design and produce lenses with a very consistent image quality of a very high order. One of the points of critique of the older SX35 ASPH was the occurrence of flare and in this area the Zeiss competition was ahead. Now Leica has significantly improved the control of flare. As the examples above show you can force the lens to exhibit flare, but you must do this with some determination. In normal situations the flare is effectively reduced to small proportions.
The images above might indicate that the differences between the SX35 and SX35FLE are small. In fact the main difference is enhanced contrast. Below you see two TIF images. Below is the SX35 in raw DNG and below that the SX35FLE in raw DNG.. Both images are at the position as indicated by the rangefinder.
Below SX35 at f/1.4
Below SX35FLE at f/1.4
