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Posterisation/banding issues ?

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  #1  
Old 04-27-2010, 03:07 PM
powaq powaq is offline
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Posterisation/banding issues ?

Hi there,

I'm new around here (well, newly registerd. Have been reading for a long time). And I'd like to start of with a big posterisation issue I'm having in one of the images I took last week.

This is a screen shot of the image at 25% zoom in PS CS4:
http://www.benoitvermeeren.be/forumpics/pic.png

You can see some posterisation banding stuff going on in the left car seat.

This is a crop from the lower left corner at 50%, still some funky muddiness going on.
http://www.benoitvermeeren.be/forump...terisation.png

But when you look at the 100% view:
http://www.benoitvermeeren.be/forumpics/100percent.png

There are no artifacts visible there (or am I looking at it in the wrong way?).

So what gives, which view is correct ? The zoomed out or the 100% view ?
Is it a display issue or an image issue? If it's a display issue, then I assume the 100% view is the correct view?

If it's an image issue: what would be the best way to correct this? There's not too much info in the RAW file left...

Oh this is what it looks like when I do a soft proof with my Epson 9800 printer profile for the paper I use on that printer:
http://www.benoitvermeeren.be/forumpics/epson.png

I'll be printing that image on lambda and not that printer. So I shouldn't be too worried about it.
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  #2  
Old 04-27-2010, 06:31 PM
anwer anwer is offline
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Re: Posterisation/banding issues ?

Tips in this link http://www.cambridgeincolour.com/tut...terization.htm
might be helpful.

Last edited by anwer; 04-27-2010 at 08:42 PM.
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  #3  
Old 04-27-2010, 09:04 PM
TommyO's Avatar
TommyO TommyO is offline
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Re: Posterisation/banding issues ?

Powaq,

I suspect your 100% view is more accurate, only exaggerated by the zoomed view. Whether you worry about it or not depends on your final print size.

However, the issue originates from the deep blacks and possible lower bit depth. Images with such deep hues are best dealt with when 16 bit. Only convert to a lower bit depth after editing. You may have meant something similar when you said, "There's not too much info in the RAW file left... Did you mean you are seeing data loss in the histogram ? The histogram is a good measure of how much data is being lost and whether posterization may occur.
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Old 04-28-2010, 12:05 AM
CanonGirl CanonGirl is offline
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Re: Posterisation/banding issues ?

I see nothing, in ANY image. Except, there is some teeeny bit of 'mottling' in the right car seat - if you smooth it out slightly it will go away.

But, I don't know if this is going to gin-orma print, or to web, or to 'normal' sized print.

I am viewing on a 19" laptop Nvidia Graphics Card on an HP HDX CT1000. SUUUPER Glossy monitor.

And a 24" Dell Monitor. A teeny bit more 'mottling'.
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  #5  
Old 04-28-2010, 07:56 AM
anwer anwer is offline
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Re: Posterisation/banding issues ?

yes there is posterization in left seat. if you cover the right side (brighter side)
of the picture with a paper you will see the posterization on left seat clearly. it seems that converting the picture into 16 bit tiff file and say in lightroom adjusting the exposure ,recovery and little bit of temperature, and may be
brush tools as well, appears to make posterization less noticeable. histogram
will have lesser spikes than what we see now.
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  #6  
Old 04-28-2010, 11:48 AM
CanonGirl CanonGirl is offline
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Re: Posterisation/banding issues ?

I am not here to 'argue' the point, the o.p was asking if we SAW it. I am saying I DIDN'T see it. And responded with what I DID see.

And I did look at ALL the images in BOTH monitors.

I'm sorry, but, I don't know how you can tell me how CLEARLY I will see it.

In my monitors I DON'T see it, and perhaps it is because mine aren't is brightly lit as the O.P's and the others who DO see it.

I did not open in LR
Nor did I open in PS CS4
Nor did I convert it to 16bitt Tiff in sRGB or RGB

I just opened it with flock, not IE8 or Safari or Firefox.

Peace

Last edited by CanonGirl; 04-28-2010 at 11:49 AM. Reason: typo
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  #7  
Old 04-28-2010, 12:15 PM
anwer anwer is offline
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Re: Posterisation/banding issues ?

i was not argueing . even i did not see the posterization at first and was wondering
where was the posterization at first place and took me one hour to see it. so my
reply was not actually to your post. i am new member and still not familiar with
buttons (post reply, quick reply etc etc of this forum). anyway i appolozise for
the incident and assure you that when posting i did not even remotely thought
that it would be taken as if i am refering to you.
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  #8  
Old 04-28-2010, 12:25 PM
CanonGirl CanonGirl is offline
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Re: Posterisation/banding issues ?

nooo I didn't mean 'literally' I mean figureatively! as in what can/can't be seen since I didn't change to 16/tiff/sRGB or RGB.

Thats all I was saying.

I am new too.

And i didn't mean to sound like a jerk. And now I feel bad! Im sorry - I didn't mean it to be taken 'that way'!

and about the clearly comment, that is why I said about the SRGB and the RGB and not changing it. And stated the monitors I was using. That is what I meant by seeing clearly!

Thank you for the note! and I didn't mean for that to sound like I was argueing, I was using it as a form of expression - maby debate should have been better?

Sorry if I am the one who came off ill-tempered!


Peace (still)!!
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  #9  
Old 04-28-2010, 12:31 PM
anwer anwer is offline
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Re: Posterisation/banding issues ?

well english is not my native language and i feel pharase (yes there is posterization)
and (you can see clearly) were not the right phrase to use. next time will be more
careful when posting.

Last edited by anwer; 04-28-2010 at 01:10 PM.
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  #10  
Old 04-28-2010, 02:17 PM
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TommyO TommyO is offline
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Re: Posterisation/banding issues ?

Powaq,
I forgot to mention.... posterization is lessened when making most initial adjustments in ACR. This is simply due to the additional headroom you have when staying in 16-bit and working on a linear gamma. Once you bring it into PS and begin applying curves or levels, you start loosing data. Posterization is also more inherent with stretching the histogram vs compressing it.
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