The M8’s very high image quality was achieved by – among other things - employing an especially thin IR blocking filter on the CCD sensor. However, this also causes a raised sensitivity to longwaved IR light. In most cases, this will not have any effect whatsoever on the resulting images. In certain situations however, e.g. when black (synthetic) fabrics are illuminated by incandescent light, these are rendered purple or dark red. Using Leica UV/IR filters on the lenses is a very simple and effective way to eliminate these effects without otherwise impairing image quality with the LEICA M8. Additionally, they protect your valuable lenses’ front elements against mechanical damage.
Using the Leica UV/IR interference filters on wide-angle lenses from 16 to 35mm causes annoying colour casts in the frame corners. Therefore, Leica recommends using coded lenses in this focal length range. The LEICA M8 recognizes 6 bit coded lenses and compensates the specific colour cast for each lens by digitally modifying the image data accordingly. With lenses beyond 35mm, the colour cast is negligible. The colour cast compensation for every 6 bit coded lens used with an UV/IR-filter is included in every firmware as of version 1.10.
In the LEICA M8, a very thin glass cover consisting of an IR blocking filter and a protective plate is
mounted on the sensor. Keeping this cover as thin as possible ensures that the lenses’ full capacity
in terms of rendition quality can be utilised. This is a result of the Leica M system’s especially
compact dimensions which lead to light rays at the frame edges reaching the sensor at
comparatively oblique angles.
On the other hand, a thin filter also results in a reduced filter effectiveness which is why the LEICA M8 displays an above-average sensitivity to IR light. Increasing the filter thickness would have led to a deterioration of the image quality, especially in the frame corners. The solution of utilizing UV/IR filters that are attached on the lenses does not reduce image quality since the filter is located outside of the optical system.
Considering the LEICA M8’s compact dimensions, the solution of employing a thin absorption filter in front of the sensor and an additional filter on the lens presently represents the best possible one from a technical point of view allowing full utilisation of the M lenses’ imaging power. As soon as alternative technologies come to market that will ensure this imaging power, Leica will make these available for our customers. Today, statements as to when and in which camera model they could be introduced cannot be made.
Professional ICC profiles allow substituting individual colours, e.g. black for purple. Theoretically, this may seem to be a solution but in everyday practise, certain colours which occur in nature, such as that of an aubergine or certain complexions, would also be influenced by such a profile. Additionally, according to tests evaluated by Leica, this would only shift the effect not eliminate it.
When textiles are coloured black, this is achieved by a high degree of colour saturation. To do so, highly concentrated magenta (dark violet), blue black, or brown red is use in the colouring baths. Especially in the case of modern synthetic fabrics such as polyamide, polyester, and polyurethane
compounds a true black colouring involves enormous problems. Due to the human eye’s imperfection the viewer registers these colours as black – even though it is only e.g. deep dark violet. Under incandescent lighting especially, these fabrics do not appear black, but rather display a distinct colour shift towards violet or also brown violet. As a result of its above-average sensitivity for infrared light, the LEICA M8 “sees” these “red” fabrics quite intensely.
In winter indoor shots under incandescent light are more common. Since these light sources have a stronger infrared proportion, the annoying effect of black colours reproduced in magenta can be expected more often. In spring and summer there are stronger IR reflections from the chlorophyll in green vegetation.
This can lead to a yellowish