LEICA Barnack Berek Blog: THE LEICA M AND LEICA M MONOCHROM SENSORS

Looking at the technical information of various top level digital cameras, it seems that everyone claims their approach to be better than anyone else’s. The quest for ever higher megapixel resolution is still in full swing with no end in sight. People are constantly told that higher resolution, more megapixels, will assure a better performance, better results.

Leica appears to have taken a somewhat more sensible approach. They have not succumbed to the pixel race. Yet the performance levels of the Leica M rangefinder cameras have proven to be some of the best available.

To understand the reasons, let’s take a closer look at the two top Leica M rangefinder models.

THE LEICA MAX 24MP CMOS SENSOR

It is interesting to see that Leica AG decided to forego the industry standard manufacturers of digital image sensors and go with a relatively unknown, European company instead. The new sensor is made by CMOSIS, a renowned European specialist for advanced CMOS image sensors. They developed a high-resolution, high-dynamic-range CMOS image sensor exclusively for Leica Camera AG. The Leica M (Tuyp 240) digital camera incorporates the full-custom CMOSIS “Leica MAX 24MP CMOS Sensor” featuring 24 Megapixels across an active sensor area of 36 x 24 mm, corresponding to the full-frame 35mm format. The sensor is the first milestone in a long term, strategic cooperation between Leica Camera AG and CMOSIS.

Guy Meynants, CTO at CMOSIS, Antwerp, Belgium, said "This is the first time that a CMOS image sensor for a 35mm high-end camera was designed, and is manufactured, in Europe for a European customer. Apart from the ceramic IC package the Leica MAX 24MP CMOS Sensor is a 100-percent European product."

The new custom-designed sensor chip is made by STMicroelectronics (STM) in Grenoble, France, using 300mm wafers in their IMG175 CIS technology. The pixel count is 6,000 x 4,000 pixels on a 6 x 6 µm² grid across the active area of 36 x 24 mm.

The sensor for the “Leica M” is based on a 6 x 6 µm² pixel size which is a relatively large area. This results in an impressive linear dynamic range close to 76dB and noticeably less noise. Higher pixel counts within the same 24 x 35 mm sensor area can only be achieved by reducing the surface area of the individual pixels along with the necessary shortcomings of smaller pixels. Pixel data of the Leica MAX 24MP CMOS Sensor are digitized by patented low-power, high-speed 14-bit column AD converters. The sensor features an electronic rolling shutter with global reset and noise cancellation through both analog as well as digital correlated double sampling (CDS) resulting in low temporal and spatial noise and non-uniformities.

STMicroelectronics took special care to reduce crosstalk between neighboring pixels for a wide range of incident light angles. The sensor reduces spatial crosstalk by its very small distance between color filters and photodiodes. Microlenses with a strong curvature and high top height focus the incoming light rays in the center of each pixel's photodiode. This allows the “Leica M” to accept the full range of high-quality lenses in the camera system.

The pixel size of 6 x 6 µm² and a full frame rate of 5fps are state of the art. The 24MP CMOS Sensor also allows Leica to offer full HDTV video recording and a live preview on an M-model camera.

The former Leica CEO Alfred Schopf said “With CMOSIS, we are very pleased to have found a partner who made it possible for us to design and construct a sensor especially for Leica. Thanks to the special sensor technology and wide pixel aperture from CMOSIS, we can now, and for the first time, offer a digital system camera that is perfectly optimized for use with both M- and R-Lenses. Leica is particularly proud of the fact that the Leica M employs a sensor Made in Europe, as a large proportion of the sensor is manufactured in France and Germany. At the same time, the extremely low power consumption of the sensor brings added benefits for both image quality and battery life.”

LEICA M MONOCHROME SENSOR - WHAT IS THE DIFFERENCE

A lot has been said about the first version of the Leica M Monochrom and, as usual, opinions differed. However, one fact cannot be argued. The performance of the camera is quite amazing. Even though the sensor of the camera has the same 18 megapixel resolution as the M9 and M9-P, overall sharpness and tonal range is visibly better.

As soon as the Leica M (Typ 240) was introduced people have been wondering if a new version of the Leica M Monochrom would be introduced, using the same sensor. This has been answered with the New Leica Monochrom (typ 246). It is equipped with a black and white only version of the CMOS sensor of the Leica M (Typ 240). Initial test have proven that the performance of this camera is unmatched.

How is this possible?

The main difference lies in the fact that the Leica M Monochrom sensor is strictly black and white. Just as with the CMOS sensor in the Leica M (Typ 240), the manufacturer is CMOSIS, and it is made exclusively for Leica Camera AG.. Color sensors need to employ a lot of tricks and compromises in order to deliver a color image with full resolution.

The front of the sensor requires the installation of a screen of color filters. Each pixel is covered by either a red, green or blue filter. Subsequently each pixel records only the color values of that particular filter. In order for each pixel to generate all colors, the missing colors are transferred from the surrounding pixels by interpolation. The image processor of the camera then has to find a compromise between resolution, noise and interpolation artifacts. All these steps adversely affect resolution, sensitivity and indirectly, noise.

Since a monochrome sensor doesn’t have to deliver color values, the filter screen is unnecessary and image information is generated without interpolation and its subsequent compromises. This enables the sensor to deliver full resolution with a performance that is 100 percent higher than the same CMOS color sensor.

The entire range of ISO values has been shifted. The maximum ISO value is 25,000, compared to 10,000 with the old model Monochrom.

It is obvious that Leica and their sensor manufacturers paid painstaking attention to detail, far beyond simply increasing pixel counts. The results are two world class sensors that need not fear comparison to anything else on the market.

For complete information go to www.leica-camera.com

To make comments or to read comments please scroll past the ads below.

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------