Photography Thailand Forum

[David Procter]

Here's the other one...

[agitlits]

David,

I must say, no. 2 is clear winner for me here! The background subject in no.1 has little effect in my opinion, where is in no.2 it make the image. Like it a lot.

Alex

[David Procter]

Thanks for your comment.

[Chris Savery]

I think this banding problem is likely caused by too few steps of gray values over that area. There is likely not enough range in the tones there for it to be spread more evenly. Drag your eyedropper over the area in question and see how many grayscale values are in use around the eye. If it is only varying by a few steps (numerically) then that would be the issue and the answer would be to try and use more - but how to do that without at the same time widening the contrast I don't know. Perhaps it would maintain better tones there if it were kept as an RGB image instead of grayscale? But even if converted back to RGB now it would not remove it and you would have to apply noise (mono) and blurr to try to soften it (just in those areas). That would seem to perhaps offer more tonal values by varyng slightly the balance of RGB (which would mean it is very slightly off gray as well).

The other thing is that posterization can be caused by a monitor that doesn't have good response and it may be helped by better calibrating the black/white levels. I have seen that when a monitor is not well setup it can exhibit banding in some tones values.

Just ideas to try. In grayscale there is only 256 values and if the face is of limited contrast it may only use a range of 4 or 5 for that entire spread of tones.
Chris :)

[Chris Savery]

I decided to take your image and look at it in PS. It seems along those bands that the values jump by 3-4 at a time from 45 to 50 to 53 to 57 so it is not because of lack of tones but something has caused it to jump  sevreral tone values rather than blend nicely in single value steps. I'm mucking around with ideas for fixing that now. One thing that is rather tedious is you can use the smudge brush with a very small radius to manually blend them and that helps. I did try adding noise and blurring but it just comes back about the same. I guess the noise doesn't alter the average tone values and so when blurred they just come back to where they were. Will see what else I can do that may help out.

It could be that in the original in-camera jpeg conversion it just doesn't have enough source tone values (in the dark tones there are very few available compared to the lighter tones), and the conversion tends to posterize them.

Chris :)

[Chris Savery]

Ok. I did play around with several ways to do this but this result is the one that was least effort and most satisfying. Hope you don't mind me doing this - I was just looking for something to do this morning...

Done like this. Make duplicate image by using Select All, Copy to clipboard. New image, Paste. (Ctrl N, ctrl V).
Blurr image fairly strongly (around 12-13) with Blurr, Lens blur (in PS CS2).
Drag the result as a layer onto original image.
Add Layer mask with Reveal All (black). Click on mask icon in layer palette (on that layer).
Use a white paintbrush, opacity 50% flow 100% (can try variations) and radiius 9 very soft and draw along the lines of banding.
Zoom in 200% and paint around until you've blended out the along the lines. A bit slow but not too much.
Wouldn't want to do for every image but not too bad for one that you want to fix up.
Can turn layer on/off to see effect. COuld also adjust opacity for layer but I didn't do that.
I could have done more but I just wanted to see if the method works.

It does show that it's possible to do and the banding is likely the result of either jpeg conversion or some process done after that. I do believe that having the raw file would likely allow more control of the conversion but hard to say.

Chris :)

[David Procter]

Thanks Chris,
I really appreciate the time you've put into helping me and I have learnt a lot from this discussion.
You've done a good job on the picture and I see no trace of the banding. Very interesting use of the eyedropper to ascertain the tonal values. I tried to mix up the pixels by cloning different pixels from different points to increase the tonal range but of you dont have the range to start with you've had it. Thanks again for having a look.
david