M240 blue sky banding when converted to monochrome

[Leica Duncan]

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Hi

 

I am having some issues with monochrome conversion. I am finding that if I try to simulate a strong red filter (that is receding the blues and perhaps boosting the reds in LR 5), I quickly developed distinct posterisation/banding in the blue areas, for instance the sky. I am working with dng files, but I have tried shooting raw and jpeg together and both file types exhibit this problem. I have also tried shooting with a polariser (in colour), the jpeg file shows distinct circular banding straight out of the camera, even the DNGs are visibly 'patchy' when viewed at 100%. Is this 'normal'? I hope not! I have tried similar edits with my D300 files and they seem to be far more forgiving. Anybody having a similar experience?

 

Thanks,

 

Duncan.

 

PS. I have search this topic without success. Apologies if this has been covered in a previous thread.

[nico1974]

Best to use SilverEfex fo your B&W conversions as this eliminates the posterisation/banding issue for me.

 

You could also try to increase the "colour noise" slider in LR - this seems to help a lot.

 

I am having very similar problems with my Nikon D800E but not with the Ricoh GR.

 

Posterisation (this is different to the noise issue) is also often visible if your display, adobe products and graphics card are not optimised for 10bit output.

 

Very useful info here - 10 Bit Output Support

Edited May 6, 2014 by nico1974

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[Leica Duncan]

Thanks nico1974.

 

I have just been experimenting with the color noise reduction and I am finding that reducing it, whilst obviously giving more 'grain', actually renders less 'blotchiness' (more descriptive than technical terminology perhaps) and thus a smoother tonal range for the files in question. Your suggestions encourage me to think that the issue is in my processing and not a problem with my camera. I think I will investigate SilverEfex next, I know many recommend it.

 

Thanks again,

 

Duncan

[mjh]

I am having some issues with monochrome conversion. I am finding that if I try to simulate a strong red filter (that is receding the blues and perhaps boosting the reds in LR 5), I quickly developed distinct posterisation/banding in the blue areas, for instance the sky.

Blue sky naturally contains very little red so in the red channel there may be just 40 to 100 levels of brightness, depending on the brightness and saturation. If you eliminate the contribution of the green and blue channels and maybe increase the contrast then in some situations, banding may be unavoidable. This effect would be less pronounced in a raw file but it would still be visible.

[Leica Duncan]

Blue sky naturally contains very little red so in the red channel there may be just 40 to 100 levels of brightness, depending on the brightness and saturation. If you eliminate the contribution of the green and blue channels and maybe increase the contrast then in some situations, banding may be unavoidable. This effect would be less pronounced in a raw file but it would still be visible.

 

Yes, that makes sense. My concern was that the kind of conversions that I am trying to make I have attempted before with other cameras, such as my D300 or my GF1 and found the banding/posterising to be less evident than with the M240 files.

 

 

Duncan

Edited May 7, 2014 by Leica Duncan

[jaapv]

Using 8 bits files if you are in Photoshop (the default setting ) will also contribute to banding. Use 16 bit Adobe RGB or Prophoto RGB. This does not apply for Lightroom which will choose the correct settings automatically.