Leica M system lens colour performance

Lens colour performance was obviously very important quality, even more important than the other quality. When changing lens, especially in the face of the face the same scene, the photographer is very sensitive to the change of colour performance.

Has the yellow or red adjustable lens is called the warm tone lens, and partial blue tone is called cold tone lens.

Some glass (such as leaded glass) contains a lot of lead oxide, and present a pale yellow. If such a glass used to do lens, then the color is warm color to move. Tonal can be appropriate coating to correct. But it is limited.

Colour performance and color reduction concept is very interesting. The human eye is difficult to as a accurate color identification instrument, because it is easy to its strong ability to adapt to deceive.

And the light will also change. Summer noon twelve o 'clock, blue of the day the sun has 10000 k, and a few hours later becomes a 6000 k. The human eye not perceive this change, but film but it can. Film of the Camera accessories is also different.

Spot light image series, was shooting scene, the colour of the lens to deduce, film and the human eye color response, has brought many variables, the discussion is interesting, but it is difficult to evaluate.

In 1983, the international standards organization issued a standard # 6728, namely: ISO color distribution index definition (ISO/CCI). As a reference, ISO organization in 1979 analysis of the 57 kinds of typical high quality lens, and use the average spectral transmission value as the basic parameters: the so-called ISO standard lens.

As a standard shoot the light, ISO USES 5500 k, it was also the emulsifying industry. This is no cloud weather in the sun on the horizon of 40 degrees when light situations. Flash and by this design, but the spectral distribution may be different.

For spectrum sensitive film, the manufacturer will for blue, green and red photosensitive layer on the sensitivity of the Camera Equipment, so that not a layer of can have normal sensitivity.

Lens, the spectral characteristics with several layers according to the average color photosensitive layer film overall effect to evaluate. In the blue photosensitive layer effect is called the lens blue shooting response. This utility response effect can be calculated.

With the relevant transmission value multiplied by blue, green and red photosensitive layer weighted spectrum sensitivity, can calculate the CCI value. General response through the additive can be. And can be respectively, blue, green, red give a numerical. For the sake of simplicity, make three numerical in a minimum of equivalent to zero. If a lens with color distribution index 0/5/4,, then this would mean that in standard lighting, the average color of the film through the lens of the camera than get no more green (5) and red (4) (relative blue (0)) layer of the response. This lens present a yellow hue.

However ISO regulation, considering the sensitivity of the emulsion industry data, the Outdoor Equipment should be identified as 0/5/4 index.

Tolerance scope is as follows:

Blue; 0 + 3 and 4

Green, 5 + 0 and - 2

Red; 4 + 1 and 2

These tolerance by triangle derived, not additive. Leica lenses aimed at the 0/5/4, when the tolerance range, is considered to be neutral.

Below is a typical leica M system lens and their CCI value. Numerical below. - / dated 4th May produce blue tone, higher than - / dated 4th May produce red hue.