Leica 50mm f/2 APO-Summicron-M ASPH. (Type 6) M-Mount Lens with Built-In Hood, Black Anodized, 6-Bit {E39} 11141

Leica 50mm f/2 APO-Summicron-M ASPH: the rangefinder standard redefined

The APO-Summicron-M 50mm f/2 ASPH is what happens when an optical engineer refuses to accept that a lens can't be made better. Eight elements in five groups, including three elements built from specialty glass formulated to bring red, green, and blue wavelengths to a common focal plane, that's the apochromatic correction at the heart of this design. The practical result is near-total elimination of chromatic fringing on high-contrast edges, which is the kind of problem that quietly degrades prints and crops at every size. At f/5.6, the MTF curves for both tangential and sagittal structures run flat, indicating no measurable image degradation across the full field. That's not a common data point.

The floating element in the rear group adjusts independently during focus, keeping correction consistent from infinity down to the 0.7m minimum focusing distance. Distortion checks in at 0.4% maximum pin cushion, functionally invisible in real-world use. The built-in hood and 39mm filter thread sit on a body that weighs 0.30 kg and measures 1.9 inches long, so nothing about the physical package betrays how much optical engineering is inside. The 6-bit coding communicates directly with Leica M digital bodies for automatic lens detection and exposure correction.

For photographers who work at print sizes where optical compromises become visible, or who shoot subjects where color accuracy on fine detail matters, this lens is the answer. It is one of the most rigorously engineered 50mm lenses ever put into a rangefinder mount, and its reputation among M-system shooters reflects that.

Who It's For

Documentary and street photographers who shoot on Leica M digital bodies get the direct benefit of 6-bit coding for automatic EXIF data and vignetting correction. Fine art and portrait photographers printing large will find that apochromatic correction keeps color fringing off sharp edges even at f/2, giving prints a cleaner, more accurate rendering. Architecture and product shooters who need low distortion will appreciate that 0.4% figure. Travel photographers working with minimal kit benefit from the 0.30 kg weight and the built-in hood keeping the package compact.

Key Features

• 50mm f/2 focal length with apochromatic correction for chromatic aberration elimination
• 8 elements in 5 groups including three specialty-glass elements
• Flat MTF curves at f/5.6 indicating zero image degradation across full field
• Floating rear element maintains optical correction from infinity to 0.7m minimum focus
• 0.4% maximum distortion, functionally imperceptible in real-world use
• 6-bit coding for automatic detection on Leica M digital bodies
• Built-in lens hood with 39mm filter thread
• Weighs 0.30 kg, measures 1.9 inches long

FAQ

What makes the APO correction in this lens different from standard achromatic designs?

Three of the eight elements use specialty glass formulated for high anomalous partial color dispersion, bringing red, green, and blue wavelengths to a common focal plane. This eliminates chromatic fringing on high-contrast edges, which is the optical problem that degrades sharpness in prints at any size.

How does the floating rear element affect performance at close focus distances?

The floating element adjusts independently during focusing, keeping apochromatic correction consistent from infinity down to 0.7m. This maintains the flat MTF curves and optical performance throughout the entire focus range.

What does a flat MTF curve at f/5.6 actually mean for image quality?

Flat tangential and sagittal lines on the MTF chart indicate zero measurable image degradation across the full field at that aperture. This is functionally the optical benchmark - most lenses show some degradation; this one doesn't.

How compact is this lens compared to older Summicron-M 50mm designs?

It measures 1.9 inches long and weighs 0.30 kg, only slightly longer and heavier than the predecessor Summicron-M f/2, yet delivers significantly superior optical performance. The built-in hood and 39mm filter thread add no practical bulk.

Will the 6-bit coding work with my Leica M film camera?

No. The 6-bit coding communicates only with Leica M digital bodies for automatic lens detection and exposure correction. Film cameras lack the electrical contacts to read this data; the lens functions normally on film bodies without any coding benefit.

How much distortion does this lens introduce?

Maximum distortion is 0.4% pin cushion - low enough to be functionally invisible in real-world use and printing at any standard size.

What vignetting should I expect at full aperture?

At f/2, vignetting measures approximately 2 stops in 35mm format (about 1 stop on Leica M8 models). Stopping down to f/2.8 visibly reduces this, with minimal light fall-off remaining at f/4 and beyond.