Raw Dynamic Range

On this page we are taking a look as how tolerant Pentax K-1 II files are to being pushed and pulled.

Key takeaways

  • Like its predecessor, the K-1 II has excellent Raw dynamic range.
  • Shadows of higher ISO files can have some artifacts and loss of detail due to noise reduction and filtering of the Raw.
  • The K-1 II sensor is ISO-invariant, but higher ISO Raw files appear to have less noise than underexposed, pushed lower ISO files. This is due to increased noise reduction at higher ISOs.
  • The K-1 II does not have a dual-gain architecture for increased high ISO dynamic range, unlike some of its peers.

Exposure Latitude

K-1 II Raws have extensive latitude, just like the original K-1 and peers like the Nikon D750. Raw files are tolerant of extreme adjustments; this 5 EV push has barely objectionable noise. However, there are some artifacts - visible as broken up text in the pushed crop - due to some filtering of deep shadows. This is not evident in the original K-1. This filtering - possibly some form of noise reduction - is likely the reason for the lower noise levels in extreme pushes compared to the original K-1. The filtering is irreversible and can leave behind artifacts and reduce contrast and detail, particularly at higher ISOs. Note the more random nature of the noise in the K-1 grey patch. It's unfortunate that this filtering cannot be turned off, as destructive processes should be saved for post-processing.

ISO-invariance

A camera with a very low noise floor is able to capture a large amount of dynamic range, since it adds very little noise to the detail captured in the shadow regions of the image. This 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 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.

At first glance, the K-1 II doesn't appear ISO-invariant: an ISO 6400 shot looks cleaner than an ISO 100 shot pushed 6 EV. However, we sent files for analysis to forum members Bill Claff, Jim Kasson, and Iliah Borg, who all confirmed significant noise reduction in Raw at ISOs 640 and above, and even some form of Raw filtering at base ISO. It's this noise reduction that makes the ISO 6400 shot cleaner than the pushed ISO 100 shot, but this also comes at the cost of detail and contrast. This is particularly obvious when comparing against the sharper ISO 6400 shot from the original K-1. Even the pushed ISO 100 shot from the K-1 II appears to have slightly less contrast than a similar shot from the K-1, likely due to some filtering even at base ISO.

In summary, given that the K-1 and K-1 II share the same sensor, we expect the K-1 II's sensor and electronics itself to be essentially ISO-invariant, like the K-1. However, noise reduction makes the K-1 II appear less ISO-invariant, but only due to forced noise reduction at higher ISOs. In fact, to retain more detail, you may be better off shooting at lower ISOs and boosting exposure to retain more detail and apply selective noise reduction yourself. Ultimately though, that's a workaround for an arguably poor decision on Pentax's part: namely, to force noise reduction - typically reserved for JPEG - onto even Raw shooters.

Importantly, the K-1 II does not have dual gain architecture, like most recent cameras from Nikon and Sony, to boost high ISO performance. Instead, Pentax appears to have chosen mandated noise reduction to give the appearance of better high ISO performance. We feel that noise reduction should be a choice left up to Raw shooters.