Raw compression can limit dynamic range
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Raw compression can limit dynamic range

Above: The a7R II does not offer a lossless 14-bit Raw option, so you may experience posterization at high contrast edges when pushing Raw files, visible in the shot on the left.

The dynamic range we've come to expect from Sony sensors allows photographers to expose more creatively. It allows one to underexpose a scene (by conventional standards) in order to protect highlights, then raise darker tones to make them visible again, as we've done here with the Nikon D810. This can lessen the need for multiple exposures and filters, which may or may not be practical for the shot at hand.

With the a7R II, Sony continues the tradition of lossy Raw files, with no option for, say, the lossless 14-bit Raw used to create the D810 image above (which comprises a Sony sensor, no less). This isn't going to affect all your photographs, but it can rear its unsightly head at high contrast boundaries of pushed files. Have a look at the area around the sign in the ISO 200 + 5EV shot at upper left vs. the native ISO 6400 shot at the right. The posterization artifacts are due to Sony's lossy compression, which you can read more about in Iliah Borg's excellent study here. You'll also see in Iliah's article that this can particularly be an issue with star(trail) shots, which tend to have sharp, high contrast transitions.

We think this is particularly a shame, especially as this camera is aimed at professionals. More so when you look at how little extra noise the pushed ISO 200 shot has compared to the ISO 6400 shot. This is because of the high dynamic range, and ISO-invariance, of the camera, which means that realistically you can save much of your image brightening for post-processing as opposed to increasing your ISO setting in-camera, which affords you stops of highlight range (which is why the sign isn't blown in the ISO 200 shot). However, you'll be limited in your ability to do so because of Raw compression, essentially meaning the camera isn't as ISO-invariant as it could be.