Infrared pollution tests
Fairly early in our testing of the M8 we noticed the now-infamous UV/IR sensitivity issue. Because image sensors are sensitive to light outside the visible spectrum, manufacturers need to use filters over the sensor to remove infrared and ultra-violet light in order to maintain correct color. Unfortunately the one used in the M8 turned out to be too weak in practical use, resulting in color inaccuracies such as black artificial fabrics being rendered as purple. Leica's solution to this was to provide screw-on UV/IR lens filters for M8 owners; this does work, but it's a rather clunky solution.
With the M9, Leica has addressed the IR problem with a redesigned sensor cover filter, which is now thicker and made from a different material. To demonstrate the difference this makes compared to the M8 we created a simple test scene lit by 800W tungsten lamps (which of course produce lots of infrared, so this is a pretty tough test). The contrast is stark - the M9 renders the scene correctly where the M8 fails.
|Leica M9||Leica M9, with lens UV/IR filter|
|Leica M8, no UV/IR filter||Leica M8, with UV/IR filter|
|Canon EOS 5D Mark II||Nikon D3X|
This key point from this comparison is that the color rendition of the M9 is at least as good as that of the M8 with a lens filter fitted (and arguably better) - it's certainly a vast improvement over the M8 with no filter. Furthermore, adding the lens filter to the M9 (to screen out any residual IR) makes only a small difference, which indicates that the new sensor cover glass is very efficient. The M9 also holds its own very well against the two mainstream full frame DSLRs in this comparison, the Canon EOS 5D Mark II and the Nikon D3X; there are slight differences between these three cameras, but at this level it's just nitpicking (all will look fine in normal use).
We've now also shot many hundreds of real-world pictures with the M9, and haven't seen a single problem which could be attributed to UV / IR pollution. Suffice to say that, to all intents and purposes, this unfortunate episode has been confined to the history books.