Fading problem

[Florin]

Hi everybody. I need an advice about a problem with the background of a new portraiture I`m doing right now:
http://i47.tinypic.com/2wqy1ch.jpg
The image is 800 dpi / gray scale / 8 bits channel.
As you can see, when I`ve adjust a little the levels, fading was lost and now I have these "bands" which can`t be smoothed. I tried all kind of blurs, I changed the mode to 16 bits channel, 32 bits channel and nothing, tried to paint the area again but no way, everything failed.
Any suggestion?

Regards

[Der_W]

Re: Fading problem

That looks like banding to me.
Does it occur in print as well?
If it does, you could try to add some noise to those areas, that'll break up the banding a little (how much depends on the strength. I'd suggest something about 0,7 Gaussian monochromatic).
Maybe you'll want to blur it first heavily (to get more uniform banding all over) and apply the noise afterwards.

[Florin]

Re: Fading problem

Hi Jonas. No, I`m not ready yet, I`m still working on it. And, I`m not printing, just deliver the final art. My cilents commented sometimes about some banding details. This banding is visible every time when levels or curves are used. In the past I used the noise, as you say, and this helps a little but just at the end, when the job is done.
The bands also appear in the RGB mode, some yellow and magenta colors sometimes.
Thank you

[mistermonday]

Re: Fading problem

Florin, the best way to avoid the banding is to edit in 16 bit. That will go a long way to mitigating banding when doing a levels adj.
Now that you have it, there are a number of ways to eliminate it. One quick method would be to select the affected area and apply a Gradient Map adj layer. Select 1 single color or two close colors (or shades of Gray) for both ends of the gradient. If the result is too smooth, you can just Filter>Noise>Add Noise; Monochromatic, Uniform, 1%.
Regards,
Murray

[Florin]

Re: Fading problem

Thanks M. I`ll try this. Let`s see how it works. As I said before, changing to 16 or 32 bits mode did not helped.
Cheers

[secretagents]

Re: Fading problem

http://www.richardrosenman.com/media...es/diffuse.zip

[TommyO]

Re: Fading problem

Florin,
I would agree with Murray's approach; I like Secretagents as well. He is correct in that once the banding is there, there is no way to reverse it. You must edit or replace that area.

Banding is caused by performing a "destructive" editing process to a rather uniform but gradient color area. The result of something like "levels" will force the existing gradient to be "remapped" over a broader area... the result being similar to interpolation... but never as smooth a gradient. So, you see banding start to occur. Another common problem is pulling a low bit-depth image into a higher bit-depth image. The low bit-depth image will often have banding after this process.

You may have a problem with a template you are using to replace backgrounds. Check those templates for banding issues, or for bit depths that may be lower than your most common edits, i.e. you edit images in 16-bit, but your templates are in 8-bit. You may need to recreate the templates and save in several bit depths. That way you can pull in whichever template that matches your current images' bit depth.

[Florin]

Re: Fading problem

Thank you so much, all of you. I like a lot the Secretagents sample. I`ll use the filters in a while.I was also ignoring the technical detail, thanks Tommy, very good explanation. I had very often this problem when use levels or curves. As I`m working with very high resolutions, 800-1000 dpi, I avoid the 16 or 32 bits mode because the image turns to hell, 200-300 Mb. On 8 bits it is more confortable. I have some first class 8 Gb RAMs but I tried to avoid an overcharged work file.
When it will be ready I`ll upload a sample.
Many thanks again

[4personnen]

Re: Fading problem

You could test adding noise on it then a small amount of blur, sometimes it's works (not garanteed) , and just one thing...is it at 100%? I know it sounds obvious but, sometimes if the displays show a smaller view it happens...

[Florin]

Re: Fading problem

Yes, I did this, adding noise. It`s a damn problem. Once it appears we have problems. Almost always when I`m using levels or curves. Thank you

[unimatrix001]

Re: Fading problem

Florin, I opened a new image at 800 dpi ran a grey to darker grey gradient then added noise to it... you could start around 4 monochromatic and go from there. Before the noise i did a levels on it the banding got real bad. added noise and there was no banding you will need to play around with the noise level to get what is comfortable for you ... btw you do really nice work.

[secretagents]

Re: Fading problem

Glad you like my example guys. I think that preventing or eliminating banding is down to one single thing: dithering, as to perceptually simulate more luminosity levels than the 256 that are actually possible with the 8 bit per channel images we always have to fall back on. On the pic I posted I applied multiple times the linked diffuse filter at a radius of about 20 on small selections until I was satisfied with the overall aspect. On some places such as the near the arrow (which shouldn't be there normally anyway) the diffusion generated unwanted artifacts which I eliminated easily with the built-in Photoshop dust and scratch filter. I also applied a little a bit of gaussian blur overall after the diffuse processing as to even out as much as possible. Of course applying too much of it would make banding occur again as it would get rid of the dithering completely.

I tried to figure out a method for dithering making use of the Photoshop dissolve blend mode but could not figure out anything satifactorily in the end.

[Craig Walters]

Re: Fading problem

i get these bands sometimes when working with smudge or 'push'. one would think you could simply lower the opacity on those brushes to smooth out the gradient, but in fact, you have to raise the opacity. just one of those things.

also, in psp, if you airbrush and use smudge/push ON THE SAME LAYER, you can get this and other weird effects, so it's always best to put those two tools on separate layers from each other.

[unimatrix001]

Re: Fading problem

Florin I found this video on smoothing a gradient. its for a blue sky but should work with what you are having problems with.
http://vimeo.com/4569340

[Florin]

Re: Fading problem

Thank you so much