Photoshop posterization problem

[decu]

Hi gues, im experiencing a problem with a photoshop posterization when im using brushes. They looks like im using a 256 color. Example is attached.
16bit RGB, Photoshop cs4, monitor nec 2190uxi, monitor is two weeks ago calibrated, gpu nvidia 8800gt. Hope for your help.

[KarimNassar]

what color space are you in? the broader the color space the more posterisation you will get. reset your brush settings in the brush palettes just in case also

[decu]

monitor is calibrated, so there is my own color space for this monitor. anyway if i change it to srgb result is the same. Brush reset too doesnt help...

[pavel123]

I am not sure how posterization with brushes work, but posterization does imply that you reduce number of colors, actually way less then 256, more like 10 or 15.

[Quantum3]

Posterization? Where?

[decu]

May be posterization is not the right word, i dont know the name of this effect.

[Quantum3]

I mean, I don't see posterization in the attachmed image.

[Quantum3]

By the way, monitors sometimes shows posterization when the zoom size is not 100%. Better try doing a print, prints have much more tonal values than monitors. If you see posterization in the print, then you have a problem.

[decu]

My monitor shows allot of tonal values, and this problem appears 2-3 weeks ago..

[pavel123]

The attached file looks pure white to me.

A more detailed description of your workflow and the issue itself could be very helpful.

[mistermonday]

Decu, The posterization has 19 perfect concentric circles from 236 to 256 with each concentric ring incremented by a value of 1 over the previous ring.. The first thought that comes to mind is that someone applied a radial gradient to a layer and then did Image>Adjust>Posterize with a value of 19. However, there could also have been many other ways that could have caused this effect. To know exactly what caused it would probably require more detail of the workflow and what was done to the image.
For those who can not see the effect, you probably need to recalibrate your Monitors or perhaps you are using LCD monitors that can not be calibrated in that range.
Regards, Murray

[mistermonday]

Other things that come to mind are combination of camera lense and jpg processing by the camera. It could also be a bad / low quality scanner. But again there may be many other explanations. So more info would be useful.
Regards, Murray

[Quantum3]

Originally Posted by decu

My monitor shows allot of tonal values, and this problem appears 2-3 weeks ago..

Didn't find so much info about your monitor, but it's a $1500 monitor. All monitors below $3000 are not professional monitors and tends to show no more than 256 tonal values per channel, meaning that these monitors are not able to show a full range of tonal values above 256 per color or gray scales. Also, all these monitors are just 8 bits of depth and also below the sRGB gamut and also, all these technical stuff represented by 72 pixels per inch, so we can say we just see quite less than a 25% of the total information held by any digital image.

These are professional monitors 16 bits made (for color and gray scale images) with a gamut a bit over Adobe RGB 1998 and they cost an eye of the face: http://www.eizo.com/global/ but still 72 PPI.

[decu]

Originally Posted by mistermonday

Decu, The posterization has 19 perfect concentric circles from 236 to 256 with each concentric ring incremented by a value of 1 over the previous ring.. The first thought that comes to mind is that someone applied a radial gradient to a layer and then did Image>Adjust>Posterize with a value of 19. However, there could also have been many other ways that could have caused this effect. To know exactly what caused it would probably require more detail of the workflow and what was done to the image.
For those who can not see the effect, you probably need to recalibrate your Monitors or perhaps you are using LCD monitors that can not be calibrated in that range.
Regards, Murray

Murray
I didn't do anything with the image, its just a white background with 19% gray brush point. Try to do this on your PC, is the result the same?

[Quantum3]

Photoshop brush is not the best thing in terms of accuracy.