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This blog entry is a summary of my testing results of a Leica Summilux 35/1.4 lens for focus shift, as well as focusing accuracy at 110 cm. This lens is no longer available new, but has quite a following for delivering "Leica Glow" (mainly veiling flare, but a magic dose of it...) wide open, as can be seen in the photo. Compare it with the images at F2 and smaller at the link below.

My Summilux is a black one made around 1983 in Canada. Since then it has been CLA'd by Golden Touch, where it was also sent off to Leica engineers in Solms, Germany, for proper focus collimation using specialized equipment for adjusting the Summilux lenses for focusing accuracy throughout all apertures.

A common issue with these older lenses that haven't been cleaned recently is excessive haze and flare, which obscures the "Leica Glow" and while this can sometimes create interesting effects, it limits the usability of the lens, especially wide open.

I tested the lens on with a Leica M8, on a tripod, at apertures of 1.4, 2, 2.8, 4, 5.6, and 8. I used a distance of 110 centimeters from the digital sensor of the M8, to the middle red Cheez It box 110 cm away, and used both tape measures, and electronic laser and ultrasonic devices to ensure the distance from sensor to the focal points indicated were accurate and square. Three additional boxes were placed to the right, and to the left of the 110 cm box. To the right of the Cheez It box, each box was successively 4.0 cm closer to the digital sensor, resulting in boxes at 106cm, 102cm, and 98cm respectively. To the left of the Cheez It box, each box was successively 4.0cm behind, at distances from the sensor of 114cm, 118cm, and 122cm respectively.

The first thing I needed to do after ensuring everything was square, and distances were accurate, was to focus accurately on the Cheez It box, using focus bracketing, where the patch for the "110 cm" marker is. The reason for focus bracketing, especially with a rangefinder and manual focus lens, is to ensure that your lens is spot on focus, regardless of what your rangefinder or scale distance indicator is showing. With older lenses like the pre-asph Summiluxes, there is usually a pretty long focus throw, sometimes 180 degrees from minimum focus to infinity. An exception is the last 50/1.4 pre-asph Summilux with the E46 sized filter ring, and 0.7 meter focus capability which has a quick 120 degree focus throw. While a long focus throw can ensure more accurate focusing capabilities, it is also possible to slightly rotate the focus ring, without seeing any change in the viewfinder. This is why examining the results highly magnified, with focus bracketing is essential for testing for accurate focus, focus shift, and indirectly resolution and sharpness. When users see "soft" images, they often assume that the lens is not as sharp as another lens. This may be the case, especially in corners versus centers of images, but is also often the result of a slight mis-focus due to the lens, camera, or user's focusing capabilities.

The results, or all of the images, which are posted here, show that the focus shift for the Summilux 35/1.4 pre-asph, is negligible when changing apertures from 1.4, to 2, 2.8, 4, 5.6, and 8, and that depth of field increases as expected for a 35mm F1.4 lens. Some other observations show that at 1.4, the image has "Leica Glow" and possibly less center and edge resolution compared with apertures at f2 to f8.

The next lenses I plan to test for focus shift will probably be the a rebuilt Former Soviet Union Jupiter 8 50/2 lens, as well as the big, big brother to this Summilux 35, the Summilux 75/1.4 lens.