The M10 Monochrom is Leica's third mono-only digital rangefinder, but the lower base ISO of the latest camera extends its flexibility.

The Leica M10 Monochrom is the company's third mono-only rangefinder. It uses an entirely new 40MP sensor, rather than borrowing the 24MP chip from the other M10 models.

We think the Bayer filter array is an amazing creation, producing results that massively outweigh its drawbacks, but there are a few reasons why going without color filters is more than just a gimmick.

Higher detail capture

The obvious benefit of a monochrome sensor is that you don't need to demosaic: each pixel you capture becomes one pixel in your final image. You don't need to interpolate missing color values for each pixel, so you don't need to call on neighboring pixels, so don't experience the slight blurring effect that this has.

The final image will be inherently sharper than most color cameras can achieve (Foveon sensors being the key exception to this).

Higher base ISO

The color filters used on most sensors absorb around 1EV of the light, since each filter has to absorb the two colors it's not allowing to pass through to the sensor (the green filter absorbs the red and blue light, for instance).

The M10 Monochrom's base ISO of 160 is lower than previous mono cameras but higher than a camera with a color filter array would be.

This means that the silicon of a monochrome sensor receives around one stop more light at any given exposure. The consequence is that it becomes saturated and clips highlights around one stop earlier, at its lowest amplification setting. The result is that its base ISO tends to be rated one stop higher than a chip with a CFA would be. On the M10 Monochrom, the base ISO is given as 160 (rather than 320 on previous models).

This can be challenging, since it means having to use exposures that are 1EV lower than you'd expect on a color camera. In bright light, this is likely to mean stopping down when you hit the M10's 1/4000th sec maximum shutter speed. But it's worth noting that there isn't any image quality cost to this.

Better tonal quality, ISO for ISO

Usually, reducing exposure by 1EV results in photon shot noise being one stop more visible (this reduction in light capture is the main cause of high ISO images looking noisier).

But, although the M10 Monochrom's base ISO of 160 means using an exposure that's half as bright as the ISO 80 exposure you'd expect to need on a color version, the Monochrom's sensor still experiences the same amount of light: there's no filter stealing half of it.

The tonal quality of this ISO 12500 shot is likely to be more comparable to that of an ISO 6400 shots on a color camera, since the sensor will be seeing the same amount of light, despite a darker exposure. The dynamic range is likely to be similar, too, since less amplification will have been applied.

In other words, you'll get the same tonal quality as a color camera shot at 1EV lower ISO. And, while the higher base ISO presents an exposure challenge in bright light, it means you get tonal quality that's a stop better in low-light situations.

And that's before you consider the fact that all noise will present as luminance noise, rather than the chroma noise that most people find more objectionable. So you get a one stop improvement in noise in low light and the noise that is present is less visually distracting, which means less need to apply detail-degrading noise reduction.

New sensor

The big unknown with the M10 Monochrom is the specific sensor performance. We've not seen a 40MP full-frame sensor before, so can't yet be sure what its performance will be like. The 24MP sensor used in the existing M10 models is pretty good, but slightly underperforms the standard set by the 24MP sensor in cameras such as the Nikon D750, meaning it's even further behind the newer chip used by the likes of Nikon, Panasonic, Sigma and Sony.

We can't yet be sure how Leica has managed to reduce the base ISO, compared to the previous model. An ISO of 160 is very low for a Mono camera, since it would equate to around ISO 80 if a color filter array was applied. So it'll be interesting to assess the dynamic range, when the camera becomes available.

We won't know how well the M10 Monochrom's sensor performs until we get a chance to go out and shoot with it. Probably out in one of the classic sports cars Leica seems to expect us to have.

All Leica has said is that the chip in the M10 Monochrom has been 'designed from the ground up with Mono in mind,' which we're a little skeptical about. It's true that we've not seen this 40MP chip elsewhere, but it's hard to imagine that (even at Leica prices), the M10 Monochrom will ever generate enough money to cover the cost of the development of a dedicated chip.

What is true, though, is that the smaller pixels of a 40MP sensor will make it less prone to aliasing than a 24MP sensor would be, since higher resolution sensors can accurately portray higher frequency detail, before getting overwhelmed and rendering an alias, rather than a correct representation. That said, simply being a monochrome sensor massively reduces the risk of aliasing (Bayer sensors sample red and blue at 1/4 their full pixel count, so can produce color aliasing with relatively low frequency detail).

Beyond the technical

It feels a bit strange writing about the technical advantages of a Leica rangefinder, since that's not historically been an area in which they've excelled, and probably isn't high on the list of why anyone buys one.

Of course, we're DPReview, so we're always going to consider the technical aspects of camera performance. But we recognize that a monochrome camera is about more than this. If you go out knowing that every photo has to be black and white, you look at the world in a different way: you start to concentrate on compositions of light and shade, not just compelling color or the warmth of the light. It's a different way of thinking.

Which is to say: we're really looking forward to getting a chance to go shooting with the M10 Monochrom.