Studio tests and samples: Leica SL (beta)

The SL represents Leica's entry in to the full-frame mirrorless segment, and it's a formidable camera in many respects. Here we take a look at what you can expect image quality-wise from the SL.*

Resolution

One of the first things we noticed about the SL was the 24MP resolution specification. We asked the Leica SL's designer why a moderate resolution, comparatively speaking, was chosen. A Leica rep expressed that anything over 24MP seemed excessive, and that the company put priority on the images and the experience, rather than the sensor resolution. Leica isn't alone in this viewpoint, but it means that the SL's resolution specification comes up well short of the highest resolution bodies from Canon, Sony, and Nikon. Instead, it lines up with cameras like the Nikon D750 and the Sony a7II (although it does not share a sensor with either) which could be considered more 'all-around' performers. This is something to keep in mind if you consider cropping ability and ultimate resolution to be important features in a camera.

JPEG Performance

Leica makes some interesting choices with respect to its JPEG processing. First, you'll note that JPEGs out of the SL are generally considerably less saturated than what the competition offers. It even appears less saturated than the Leica Q. Also of note in comparison to the Q are the more magenta shifted reddish tones: compared to the Q, this woman's face appears less yellow and more red-shifted. The SL, in fact, generally appears to have a slightly stronger magenta rendering compared to other cameras, evident in Paul's coat. This appears to arise from less orange shifted reds. Although opinions will vary, what all this means is that some of us in the office thought skintones could be improved in default JPEGs.
The biggest difference in Leica's JPEG engine compared to its competitors is arguably in its noise reduction. A look at ISO 6400 shows the SL removing mostly chroma noise, while leaving significant luminance noise behind, giving JPEG images a grainy look. Whether or not one prefers the grainier look reminiscent of higher speed film is a matter of personal taste, but the preservation of noise grain is something few other camera makers have embraced. Less aggressive noise reduction means better detail retention at high ISOs, so high ISO JPEG images aren't a smeared mess. If you can stomach the graininess, the SL produces potentially usable JPEG images at ISO 12500 and possibly even at ISO 25000, where the competition has smeared away details and blurred colors with noise reduction. This choice, as we saw in the Q, seems to be a deliberate nod to both heritage and customer base from Leica.
Interestingly, chroma noise reduction appears to be pretty aggressive, which ends up significantly desaturating high ISO JPEGs. Combined with the lower saturation of JPEGs to begin with, users may be somewhat displeased by the lackluster default JPEGs under low light. Thankfully, though, you can switch to Raw.

Raw Performance

We'll address Raw dynamic range on the following page, but here we'll take a look noise performance in Raw. A comparison at ISO 6400 shows the difference between the SL and its ~24MP competitors. While it is on par with the Sony a7II, the SL falls behind the Canon 6D and isn't quite competitive against the class-leading Nikon D750. Performance is similar to the Q, which isn't surprising given that the cameras likely use the same sensor. Up at ISO 25000 the results are the same, even though the ISOs are named differently between the cameras. Compared to top performers, the gap between the Leica's sensor and the competition becomes more evident, with the higher resolution a7R II, as well as the low light-oriented a7S, showing significantly less noise than the Leica.

Take Home

While the Leica SL has many strong points, raw image quality, while certainly respectable, falls behind class-leaders with respect to JPEG color rendition, Raw noise performance in low light, and Raw dynamic range - the latter of which we'll take a look at on the next page.

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Note on Color and Lens Performance
Note the Leicas use .DNG files that have an embedded color profile, meaning that neither of the Leicas are using the 'Adobe Standard' profile, giving them different colors and contrast than the files that used the profile when processed. Also, while the center sharpness of the new 24-90mm zoom used on the SL at our standard focal length and aperture certainly isn't bad, primes still tend to be sharper and more consistent across the frame. The Leica zoom costs the SL some apparent sharpness compared to competitors in the center, and definitely struggles in the corners, much like the Samsung NX1 with the 16-50mm S lens. As the 24-90mm is the only lens available for the SL at this time, our options were constrained.
* 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).