Author Topic: Posterization problems (Read 4158 times)

PaulieWalnuts · « **on:** December 19, 2007, 13:06 »

I'm having some problems with posterization (example http://en.wikipedia.org/wiki/Posterization). It's nowhere as bad/obvious as the Wikipedia example but can be seen faintly in shadows when viewed at 100%. It's really obvious at 200%.

I've switched to shooting RAW with my Nikon D80 and convert the NEF to a PSD with ACR and then the final is saved as a 8-bit JPG. I try to nail exposure while shooting and make minimal adjustments in ACR and PSE. This has helped but it's still a time consuming pain to paint/smudge the posterized shadow blobs. If I don't like the quality of the end result I don't even bother submitting it anywhere. I spent three hours shooting last Saturday and scrapped most of them because they would take too long to fix.

I'm guessing it's something in my workflow that is causing this. If it's equipment, then I may upgrade (D300?) or even switch (40D?).

Anybody else running into this and have suggestions?

Paul

sharply_done · « **Reply #1 on:** December 19, 2007, 14:04 »

It helps to introduce a small amount of localized monochromatic noise (2%?) on a neutral gray layer set to Overlay blending mode. You can also try using the clone tool set at softest and 15% to 40% opacity to blend posterization lines. Avoid using the blur tool, as it tends to introduce posterization. The smudge tool can sometimes be of use, too, but not that often. Downsizing may also help rescue an unusable shot.

I'm a bit curious about your "nailing the exposure" statement: you should be aiming to overexpose your images as much as possible without blowing the highlights, then bringing the exposure back to something acceptable by adjusting the levels.

hatman12 · « **Reply #2 on:** December 19, 2007, 14:55 »

Nazdavie, in addition to sharply_done's suggestions, please check that you are not using colour space sRGB either in your camera or in Adobe (or other processing application). sRGB uses a more limited colour bandwidth. You camera and Adobe should be set to use Adobe RGB.

Naturally you shouldn't be using 'web colours only' when you save files.

You shouldn't be getting these problems with your Nikon so it is something in your processing method.

fauxware · « **Reply #3 on:** December 19, 2007, 16:25 »

I m using D80 and I never had this kind on problem so far.
I expose to the right as sharply_done says (great advice to reduce noise too), I convert with ACR or Nikon Capture NX in 16 bit tiff with Adobe RGB color space and then save as jpg 8 bit minimum compression.
I hope this can help you

PaulieWalnuts · « **Reply #4 on:** December 19, 2007, 19:05 »

Sharply - I shoot and make adjustments until non-white highlights blow and then back off a step or two. At that point the histogram is normally spread evenly and hitting the right side. I've seen complaints that the D80 exposure is hot but mine tends to underexpose a bit. My rejection rate is pretty low but that's probably because I've learned not to waste time on questionable images.

Hatman - I've been alternating between sRGB and Adobe RGB. Adobe RGB does seem to reduce the issue but not eliminate it. I'm saving as JPG at 12 quality.

Fauxware - Can you do me a favor and check your finished JPG shadows at 200% and let me know what you see?

Thanks for the tips!

ale1969 · « **Reply #5 on:** December 19, 2007, 19:21 »

Quote from: hatman12 on December 19, 2007, 14:55

Nazdavie, in addition to sharply_done's suggestions, please check that you are not using colour space sRGB either in your camera or in Adobe (or other processing application). sRGB uses a more limited colour bandwidth. You camera and Adobe should be set to use Adobe RGB.

Naturally you shouldn't be using 'web colours only' when you save files.

You shouldn't be getting these problems with your Nikon so it is something in your processing method.

Take in count that if you shoot in raw, color profiles are decided upon conversion time. Raw files don't have an embedded color profile so the camera settings just influence their jpg preview.

At the very end you have to grown accostumed to the LCD display of the D80 and don't blindly trust it.

For example most of the time when it warns you about overexposure it's not likely so, there is a "safe" zone before real overexposure and I sometimes managed to gain about a 2/3 stop exposing to the right (with the obvious great results in natural noise reduction and expanded color dynamic range).

I'm still messing with it and there's really very little rules beside experience, so when in studio shots I feel free to bracketing to the right as much as possible, in "shot now or never" situations better feel safe and maybe just add the 2/3 stop of the d80 underexposure meter.

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Author Topic: Posterization problems (Read 4158 times)

PaulieWalnuts

sharply_done

hatman12

fauxware

PaulieWalnuts

ale1969

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