Posterisation/banding issues ?

[powaq]

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.

[anwer]

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

[TommyO]

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.

[CanonGirl]

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'.

[anwer]

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.

[CanonGirl]

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

[anwer]

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.

[CanonGirl]

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)!!

[anwer]

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.

[TommyO]

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.

[CanonGirl]

Again, Anwer, no worries, my sincerest apologies. It was a mis-understanding on both of our parts. I'm thinking more so on my part!

Again, nice meeting you - and I used the wrong words myself, and I apologize if i mad you feel less than appreciated for you contributing to the group.

Peace Anwer!!! peace!!!


Best,

Kimberly

AND MOST IMPORTANTLY... I hope that the OP (which stands for original poster.. I hope he can get his issue taken care of !!)

As my observation was probably not value added.

thanx again Anwer

[Quantum3]

I have replied to this topic many times, so forgive my direct speech.

1) Monitor is responsible of banding.
2) Bit of depth too.
3) Zoom too.

1;3) See the image at full pixels and check again for the banding.
2) take the pics in RAW 12 or 14 bits and edit in 16 bits.

Do a print, probably the picture is right, whatever would be the bit of depth or the monitor you use.

Mart

[powaq]

Thanks for the replies already guys!

Sorry for my late reply but I've been real busy the past few days.

Bit depth is not the issue, all my pictures are taken with a D700 in 14bit RAW and edited in 16bit. There is no point in using 8bit, I never use it. I only convert to 8bit when outputting for the web or a printlab that doesn't support 16bit files.

What I meant with "There's not too much info in the RAW file left..." is that the left side of the image is slightly underexposed (I was lying in front of the fill flash in the trunk of the car so I stopped some of the light coming through, my own stupid mistake). Bringing up the exposure in Aperture (or ACR, I use Aperture mostly) results in a greyish image. I already added a layer with a slightly higher exposure for the backside of that seat. So going even further results in a) the left side is too bright, making it unnatural and b) introduction of noise/artifacts etc.

This is my histogram:
Spiked histogram

This is my histogram after pressing the warning triangle:
Smooth histogram

The smooth histogram looks great I think, no spikes going on. (a lot of the black is caused by the black "widescreen" bars I think).
Either way I'll bring it in this week for a lambda print. We'll see from there.

Actually my main question was: *what if* I can't get anything usable out of the RAW file anymore and I have to fix the posterisation ? Just for any image in general. Not necessarily this one.
Do I add noise to a layer and mask it ? Do I noise a channel, blur somewhat? Paint? Any ideas?

[TommyO]

Originally Posted by powaq

Do I add noise to a layer and mask it ? Do I noise a channel, blur somewhat? Paint? Any ideas?

Not something I deal with a lot. But, from a technical perspective, I think it would depend on the colors you are dealing with.

For blacks (as in this case) you may wish to desaturate to remove contaminant colors. (Verify in CMYK)That alone may do it. If not, then isolate and repair; the repair method dependent upon the situation... i.e. solid, gradient, etc.

Just a thought.