Bad RAW implementation in the NX 20MP cameras!

Started Jul 24, 2012 | Discussions thread
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dlacoutu
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Bad RAW implementation in the NX 20MP cameras!
Jul 24, 2012

Well, you've all seen the "weird color circle banding issue on NX200" thread...

Having seen some strange shadows posterization effect myself in shots that should be okay, I've spent some time trying to understand the problem.

Facts I've been able to reproduce:

  • the circular posterization effect appears only with NX lenses, on dark pictures,

  • a shadow posterization effect (anywhere in the frame, regardless of the lens used) can be obvious at 100 iso even in JPEG, then gradually disappears with higher iso.

  • any shadow lifting, even gentle, shows these ungainly posterization bands in shadows.

From my limited knowledge of RAW format, it seems that Samsung does a two-step "optimization" on the RAW data, prior to the JPEG conversion:

  • first "optimization" is to clip shadow data under a given threshold (to limit the RAW file size?).

  • second "optimization" is to apply a vignetting correction to the RAW data, for given lenses.

They are made in this order, as you'll see below...

This behavior creates two problems.

First problem is that you cannot do any shadow adjustment in post-processing, even on the RAW file.

Take the following example: these two shots were taken using the same aperture and speed.
First one taken at 800iso:

Second one taken at 100iso then pushed +3Ev in post-proc:

The 100iso shot should end up roughly identical to the 800iso shot, but you can see by yourself what happens in the shadows...

Both shots were processed using Samsung RAW converter, but you get similar results with RawTherapee and Adobe Camera RAW.

Second problem is that, on dark pictures, the vignetting correction actually add its own vignetting "banding" to an already badly beaten up RAW data. As the shadow data is already clipped, the vignetting correction actually appears as discrete banding all around the picture, as seen in the other thread...

Funnily, using an higher ISO value actually helps hiding these ungainly posterized shadows, as the added noise does not get clipped in such a way.

So, in their current state, low-iso RAW files from the NX200 and NX210 are nearly impossible to handle properly, and even the slightest shadow lift will show these artifacts.

From what I've seen, there is no reason to think that the NX20 and NX1000 will behave differently.

So, Samsung, please, fix this!!! Your cameras are otherwise excellent, but this is a major bug!

 dlacoutu's gear list:dlacoutu's gear list
Samsung NX100 Pentax K-5 Samsung NX200 Pentax smc FA 50mm F1.4 Samsung NX 30mm F2 Pancake +6 more
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