Leica hasn't been explicitly clear about where the 24 megapixel sensor in the SL comes from - only that it's a modified version of the sensor used by the Q. This means it's likely the same CMOSIS sensor in the Leica Q that we demonstrated to exhibit banding in pushed shadows. This ultimately limits the dynamic range of that camera, and we'll take a look at if the same holds true for the Leica SL*.

In the interests of fairness, we should note here that Leica has informed us that a future firmware update may make a difference in this regard. As such, we'll revisit these tests when the time comes.

Exposure Latitude

In our first test, we look to see how well the Raw files tolerate pushing. We've done this by exposing our scene with increasingly lower exposures at the camera's base ISO of 100, then pushing them back to the correct brightness using Adobe Camera Raw. Taking a look at the effects on shadow areas allows us to assess the exposure latitude (essentially the dynamic range) of the Raw files.

There are two factors at play here, which can't be entirely separated. Less exposure means less light is captured, meaning that shot noise is more visible. This means that the images would get noisier even if the camera was contributing no noise of its own. This theoretical 'perfect' sensor doesn't exist so, after a certian point, the noise contribution of the camera may also become visible.

Because shot noise is primarily dictated by the total amount of light captured, it is highly dependent on both exposure and sensor size. This means that, if sensor efficiency is similar, the results are only really comparable when looking at cameras with the same sensor size.

Looking at the SL versus the Q, we see that performance is very similar between the two cameras. Compared with the Nikon D750, the SL is a tad bit behind, showing more noise, at even modest pushes of 2 or 3EV. Beyond that point, the differences become more dramatic, as the SL begins to show increased noise and banding relative to the D750 at 4 to 6 EV pushes. This performance should be seen in context, though: the SL offers slightly better performance than files from the Canon 5DS R or 6D when it comes to pure noise levels at common output sizes. Note, however, that banding in the SL will ultimately limit the quality of these shadows, and is generally harder to remove with noise reduction or by downsampling your image to smaller sizes.

ISO Invariance

The exposure latitude test above includes both shot and read noise effects to give a real-world perspective on how far you'll be able to push the shadows in, for example, images of high contrast scenes exposed for the highlights. However, to get a clearer idea of sensor performance (and of the degree to which the sensor benefits from ISO amplification), we need to compare images shot at the same exposure, but different ISO settings.

Below we've used the same aperture and shutter speed at different ISO settings to see how much difference there is between shooting at a particular ISO setting (and using hardware amplification) or digitally correcting the brightness later. Using the same exposure means that all the images were created from the same amount of total light (so have the same shot noise). This means that any differences in noise must be the result of read noise added by the camera. A camera with low downstream read noise, which usually translates to high dynamic range, will show little to no benefit to using hardware amplification vs digitally correcting brightness later. Saving the brightening for a digital push in post allows one to decrease the ISO setting at the time of exposure, potentially preserving stops of highlight range.

With modest pushes at higher ISOs, we can see that the Leica is performing similarly to the Nikon. At the exposure we've chosen for the cameras (optimal for ISO 6400), the SL does show a tad more noise than the D750 due its slightly worse ISO performance, which we expounded upon on the previous page. However, the ISO 3200 + 1EV, ISO 1600 +2EV, and ISO 800 +3EV shots don't look too dissimilar from the ISO 6400 shot shot, which means the SL, like the D750, is relatively ISO invariant from ISO 800 upwards (like the D750).

However, drop below ISO 400, and the SL is no longer ISO invariant. Shadows of ISO 100 and 200 shots (pushed 6 and 5 EV, respectively) show significant banding, due to these shadow tones falling below the noise (and banding) floor of the camera. In comparison to the class-leading Nikon D750, banding and general noise levels are considerably worse for pushed shadows of low ISO shots, which means that dynamic range is limited. Put another way, the Leica SL is not ISO invariant: it doesn't have so little downstream read noise that you can shoot at base ISO and push the results later in order to give yourself extra highlight headroom (cameras are generally capable of recording their widest dynamic range at base ISO). Instead, it benefits from a little hardware amplification to lift all the data you might want to use above the camera's noise floor.

Put in perspective, though, the Leica SL still does demonstrate pretty solid performance - its files appear to offer greater dynamic range than Canon's EOS 5DS R or 6D, for instance. However, its shadow performance can be significantly undermined by the hard-to-correct-for banding.

What's This Mean?

The Raw dynamic range of the Leica SL shows some significant limitations. It falls well behind class-leaders like the Nikon D750, D810, or Sony a7R II (scroll back up to widget). However, from purely a random noise level, the SL shows more dynamic range than a comparable Canon full-frame camera. However, the reality is that banding creeps in pretty early in shadows at low ISO settings, which will limit the real-world 'push ability' of shadows.

What this ultimately means is that you'll be limited in your ability to decrease exposure to expose so as to not blow highlights in high contrast scenes, because you'll be limited in your ability to correct (brighten) dark tones in post-processing. Do note that at higher ISOs (800 and upward), you probably won't notice these limitations in the slightest, though you will be limited, in such low light situations, in your ability to decrease the ISO setting to preserve highlight detail, as the camera is fairly ISO-variant.

* Please note that the Leica SL that we used for these tests is a near but not final production camera running pre-production firmware. As such, image quality may not reflect the output of final shipping cameras (although it is likely to be very close).