The Pentax K-1 has produced one of the best dynamic range performances we've yet seen. As our testing of the camera continues, we've been looking through the results of our Raw dynamic range test and we've been very impressed. And that's before we looked at the benefits brought by Pixel Shift Resolution mode.
Raw Dynamic Range
Exposure Latitude
In this test we look to see how tolerant of pushing exposure the Pentax K-1's Raw files are. We've done this by exposing our scene with increasingly lower exposures, then pushed them back to the correct brightness using Adobe Camera Raw. Examining what happens in the shadows allows you to assess the exposure latitude (essentially the dynamic range) of the Raw files.
Because the changes in this test noise are primarily caused by shot noise and this is mainly determined by the amount of light the camera has had access to, the results are only directly comparable between cameras of the same sensor size. However, this will also be the case in real-world shooting if you're limited by what shutter speed you can keep steady, so this test gives you an idea of the amount of processing latitude different formats give.
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Compared with the Nikon D810, the Pentax does a great job. There's less chroma noise visible after a 5 and 6EV push, suggesting the Pentax is adding even less noise to its images than the already very good Nikon. It's a similar story when compared with theNikon D750. The difference compared to the Sony a7R II is even greater, marking the K-1 as one of the best results we've ever seen.
The picture is slightly muddied by the D810 offering an ISO 64 mode, which can tolerate around 2/3EV more exposure before clipping, allowing longer shutter speeds that provide a shot noise benefit commensurate with that. This allows the D810 to pull almost imperceptibly ahead in brighter, shot-noise limited tones, but doesn't stop the K-1's result (from a camera with a list price roughly half as much) from being hugely impressive.
The difference is even bigger in Pixel Shift Resolution mode. Because it samples the scene multiple times, it effectively collects more total light, which means less shot noise. As you might expect, the result from the four 1/320 sec exposures used to create the 1/320 + 6EV image show similar levels of noise to the 1/80th second exposure shot in single image mode (a 2EV advantage), only with the greater sharpness that Pixel Shift mode brings. This lower noise means you can push the files to a tremendous degree - far beyond what the Nikon D810's ISO 64 mode allows.
ISO Invariance
A camera with a very low noise floor is able to capture a large amount of dynamic range, since it add very little noise to the detail captured in the shadow regions of the image. This has an interesting implication: it minimizes the need to amplify the sensor's signal in order to keep it above that noise floor (which is what ISO amplification conventionally does). This provides an alternate way of working in situations that would traditionally demand higher ISO settings.
Here we've done something that may seem counter-intuitive: 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) vs. digitally correcting the brightness, later. This has the advantage that all the shots should exhibit the same shot noise and any differences must have been contributed by the camera's circuitry.
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You can see all the K-1's full ISO Invariance results here and its pixel shift results here. The K-1 is as close to being ISO Invariant as we've seen, meaning there's no cost to shooting at ISO 100 and pushing the files later, rather than using a higher ISO. This means you can keep the ISO down and protect multiple stops worth of highlight information that would otherwise be pushed to clipping by the hardware amplification.
ISO invariance isn't an end in itself: there are cameras such as the Sony a7R II that are ISO variant because their higher ISO results are so good, not because their low ISO DR is deficient. However, a look at our standard test scene shows its high ISOs are extremely good, so you're not losing much in comparison with these dual-mode sensors. The K-1's files have a very high level of flexibility when it comes to processing.
Conclusion
In conclusion, the K-1 gives one of the best Raw dynamic range results we've ever seen, when shooting in single shot mode and absolutely outstanding results in circumstances where you can use the pixel shift mode. The multiple sampling of the same scene effectively gives a 2EV dynamic range boost, meaning it out-performs both the D810 and the 645Z by a comfortable margin. Less noise (though multiple captures) and multiple 14-bit values at every pixel mean it can give outstanding levels of DR for static scenes where you can use the Pixel Shift mode.
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