Optical considerations, Image | Leica R-Lenses manual

Chapter 7

Leica R-Lenses	4

allow the people at the assembly line to hand adjust the compensator mechanism in such a way that the lens is always at optimum performance. Every single lens is being checked to perform as designed and especially the aspheri- cal elements are very carefully adjusted. The result is a much lower tolerance band than would normally be possi- ble. The care that is being lavished on the quality of the assembly can be read off from the time needed: it takes a worker more than two hours to assemble the lens. This close cooperation between design and assembly is one of the main causes for the consistently high quality of the Leica lenses and has now been brought to a new level. The assembly and adjustment instructions are part of the final lens design and the design is adapted to what is the best assembly practice.

No two lenses that leave the factory are absolutely identi- cal. There is always some tolerance during manufacture.

The factory must set the lower limits of the performance that they can accept as being within the requirements as specified by the designers. A long as these requirements are met, a lens will be accepted by quality assurance. With the construction of the LEICA VARIO-ELMARIT-R 28-90 MM F/2.8-4.5 ASPH the statistical distribution within the tole- rance range is significantly reduced.

Zoomlenses are difficult to manufacture to narrow toleran- ces because of the lens groups that have to move in a com- plicated path. Normally one uses a mount with guiding slots that govern the movements of the lens groups in relation to each other.

In most cases there are two or three slits and they are mil- led in the mount as open holes, in which the guiding rollers move. With open slits, however, the structural integrity of the mount can suffer, but with two slits and sufficiently thick walls, there is no problem. The price you have to pay is a heavy lens. One of the requirements for the new lens was its low weight. In this LEICA VARIO-ELMARIT-R 28-90

MMF/2.8-4.5 ASPH we have three moving groups and the- refore three guiding grooves. Now we cannot use the nor- mal construction. (too heavy and/or too fragile). To ensure the necessary stability, one cannot use the open slit method, but must use internal grooves that can only be cut by special CNC machinery that Leica developed in coopera- tion with Weller, the leading manufacturer of this type of CNC tools. The milling movement creates a surface rough- ness that has to be smoothed to a tolerance depth of 0.01 mm to ensure that the guiding rollers move with the same resistance over the whole range. The mount of the new lens is made of quite thin and very high-grade aluminium that is specially selected to have the required stability. It is also

selected because the surface reacts quite well to the black anodizing process (see image 1).

(image 1)

The result of all this effort is a lens with a very smooth movement of the focusing ring and focal length selection. With quite sensitive fingers one can feel some instances of friction when you go from 90 mm to 28 mm, so perfection is always relative.

__Optical considerations

The general image quality of this lens is of a very high order. Leica characterizes the lens as a travel and general purpose lens. This is undoubtedly true, but I would add that the performance of the LEICA VARIO-ELMARIT-R 28-90 MM F/2.8-4.5 ASPH does support professional photography of a very high calibre.

At 28 mm and full aperture (2.8) we have a high contrast image that can record above 150 Lp/mm in the centre of the image and more than 80 lp/mm in the outer zones (see image 2). Only the corners are weak with a soft recording

R-Lenses specifications

Leica R-Lenses have long been revered by photographers for their exceptional quality and performance. Designed for use with Leica R-series film and digital cameras, these lenses embody the brand's commitment to optical excellence, precision engineering, and user-friendly functionality.

One of the most notable features of Leica R-Lenses is their superb optical design. Each lens is crafted using high-quality glass, often featuring special elements such as aspherical glass and low-dispersion lenses to minimize aberrations and enhance sharpness. This meticulous attention to optical performance ensures that images captured with R-Lenses exhibit remarkable contrast, clarity, and color fidelity, allowing photographers to achieve stunning results.

Another key characteristic of Leica R-Lenses is their robust build quality. These lenses are constructed with durable metal housings, ensuring they can withstand the rigors of professional use. The precision of the manufacturing process results in smooth focus and aperture adjustments, providing photographers with a tactile and reliable shooting experience. The use of weather-sealing in certain models allows for shooting in challenging conditions, further enhancing their versatility.

Leica R-Lenses also feature a distinctive aesthetic, characterized by their sleek design and distinctive red dot logo. This iconic branding signifies a level of craftsmanship and quality that is synonymous with the Leica name. The manual focus mechanism on R-Lenses is particularly praised by many photographers, as it allows for fine-tuned control over the focal point, which is especially useful in portrait and macro photography.

In addition to their optical and mechanical excellence, many Leica R-Lenses come equipped with advanced technologies. For instance, some models include the ROM (Read-Out Memory) contacts, which enable the camera to communicate with the lens for enhanced functionality, including automatic aperture control and accurate exposure readings. This integration of technology with traditional craftsmanship exemplifies Leica’s approach to modern photography.

Ultimately, Leica R-Lenses offer an unparalleled combination of optical brilliance, robust construction, and user-friendly features. With a range of focal lengths and specializations, from wide-angle to telephoto, photographers can find the perfect lens to suit their creative vision. Whether one is capturing landscapes, portraits, or close-up details, Leica R-Lenses provide the quality and precision expected from one of the world’s leading camera manufacturers.