how to avoid "color banding" "banding" and "posterization" ?

[pure]

how do you avoid "color banding" "banding" and "posterization" ?

i got some critics from an image stock-company like "gettyimages"
when they inspected my retouched images

additionally they mentioned

"blurring in the sky"
"no neutral blacks"
"The shadow read too heavy"
"Inconsistent noise"

what could this mean please? "blacks should be around 3-10 and not 0, like in your images"


thanks

[Swampy]

What resolution are you working at? Is this for prepress? It should be a minium of 300 DPI (ppi).

Banding is usually associated with gradients. Were you trying to run a gradient across a large area (like a full 8.5 x 11 spread)? Even at high (prepress 300 ppi) resolutions you can get banding. If applied as a layer or mask, try running a slight gausian blur on the gradient.

"blurring in the sky" There is probably luminacity artifacting in the sky so you need to fix it
"no neutral blacks" I don't understand their terminology
"The shadow read too heavy" Shadow areas call for too much black on the printing plate.
"Inconsistent noise" JPEG artifacting, run something like NeatImage or NoiseNinja

"what could this mean please? "blacks should be around 3-10 and not 0, like in your images"? Check your levels dialog box under "Options". to see where you have black/white set for clipping. Most printers want at least .10% for each. Also make sure your Color Settings are set for something as shown below for process printing.

[Ant]

Don't blur your sky without graining/noising it up to match the grain/noise that is in the original image. Make sure your shadows/blacks are not blocked up and have printable detail *a better option than 3-10 is just to stick around 8 - look in your info pallette and see what they are reading and adjust them accordingly. Make sure your blacks are not cast in color - look again in your info pallette when you bring the color picker over the black areas - they should be more or less equal when it comes to the numbers of the colors.

Google banding. It occurs when colors overlap - most likely something you are doing in post is causing this. Sometimes, a little noise can help, but don't go above 6 generally. Other times you have to selectively blur and clone and heal and dodge and burn to remove it. Sometimes you have to do all of the above. If you can live without whatever you are doin to the file that is causing it, don't do it.

You are really messing with things beyond where they need to go if you are getting posterization. This could also mean a lot of things depending on who is using this term and if it is being used correctly. check Google.

[Ant]

http://en.wikipedia.org/wiki/Color_banding
http://en.allexperts.com/q/Adobe-Pho...ing-images.htm
"When banding occurs in images, it can be mistaken for posterization, but it’s more complex than that. Banding is caused by the failure of an algorithm during an image conversion, such as switching to a new color mode. If too many near-identical image tones spread out farther than its computational area, the algorithm can fail, and the conversion may produce tonal edges called bands. To eliminate banding, use the Add Noise filter to add pixel variation to adjacent tones........"
http://www.graphics.com/modules.php?...icle&artid=371

[pure]

thanks for that quick help!

i work at 300dpi, 5100pixel wide images from a canon 1ds mark II. they have around 48MB as TIFF.
i develop with phase one, leaving it untouched in developer and retouch it in CS2 or 3 (colorspace adobe-RGB)

usually the photographer used also a greycard.
first step for me is to open the greycardimage, duplicate it over the image i retouch and use a levels-layer, selecting the medium picker and picking one point in the image with/in the greycard to get the right grey balance, then i use about 5 or 10 or 20 masked levels-layers to adjust the contrast by alt-clicking into the levels-window and later i also change the colors of the skin or the sky (less red/yellow skin usually and less magenta in the sky)

i can report that i get banding or noise even if i only use one layer with lets say changing the sky from redblue to greenblue, then i see the banding stripes in the sky. is that normal? the more level-layers i use, the more banding i can see.

- in detail, what are you doing when the color picker reads color in the blacks? (if the numbers are not equal)

- one possible solution i see is to develop 24bit images instead of 16 bit.
would that prevent banding? i dont know. but working is only as half as fast as with 16bit images (saves very long, needs much ram and so on)

[Swampy]

The number of layers should have nothing to do with artifacts / j'peging. What resolution do you have your monitor set to? You didn't say wheter PC or Mac, but if PC, do you have an upgraded graphics card?

I set black in the color picker to RGB 0-0-0.

I don't think bit depth is an issue. If you are seeing considerable banding on the screen, I would say it's a graphics card/monitor resolution issue. I work on a Mac with a 20" Apple display set to 1680 x 1050 and millions of colors. I've never seen banding on my screen when working with high resolution images. May get it when I print, but that's because my Postscript laser only does 1200 DPI where as a 4 color press is gonna do 2400 DPI or better.

[Godmother]

I'm happy for you Don't know what's happened in your life but it sure has improved your comments.

[Swampy]

Excuse me, Godmother?

[cricket1961]

Keep your blacks around 5-5-5 or 10-10-10 and not 0-0-0.
The companies need to have room when conversions are done to keep detail and avoid plugging on press.

Chris

[NancyJ]

You can alter your black-point in photoshop levels to be something other than 000 so when you run your levels adjustment it will use whatever figure you choose as 'black'

Edit: Looks like swampy beat me to it - that'll teach me for posting when I'm in a hurry

[pure]

swampy i also work on an imac 24" and a connected 20" apple cinema display, which is calibrated well. the imac is only for the palettes. the people who want to buy the images
report that banding in my images when we sent a few to them for inspection.

the banding usually appears quick as i relatively often work on beach images, the models are usually underdeveloped and the sun is very strong. banding appears in the sky when i remove the magenta from it to make it more moody.

i would like to know which number you mean in the levels window, the one below or the one in the middle on the left each...? (output or input)

do you set the black point for each image you work on, i guess, by moving the slider to 10 and not to 0, like its shown in my window, the number below. (outputlevels) (0 – 255)

thx

[Swampy]

Pure, Are you shooting in RAW? Just curious.

Is it banding or luminance artifacting? I'm no photographer, but are you using any kind of filters in the strong sunny situations?

To set your black and white clipping points in Levels... go to the Levels Option button and set the b/w points there.

[TheVeed]

swampy and ant give excellent advice.

If banding is occurring because of a color move, sometimes it helps (like Ant has discussed) to bring noise into it.

What I do, is I'll add noise to the mask, which sometimes really helps. I usually add 4-10, but generally stay within 6-8, depending on the file size, then I use the Fade Filter and set it to Luminosity. That way, you only get the grain in the greys of the mask, which has worked well for me.

Try it out, see if it works.

[pure]

wow thanks swampy
some more detailed questions if you like:

is it stored there in the levels options "forever" or do i have to change it
for every image? also, does it only affect when i do auto-correction, as there is written auto in the box ( i dont work with auto-corrections)

you have added 0.10 there. (why exactly that number please?) are these the 2 boxes i have to set to 8 or 10?
like someone mentioned before...i quote : "Check your levels dialog box under "Options". to see where you have black/white set for clipping. Most printers want at least .10% for each."


for the banding, i also added noise (gaussian at 3) today, and it helped i guess.

(yes i get raw images, i develop with phase one or CS2, sometimes i only get JPGs, but rarely, and the photographers are shooting with a H1 Hasselblad or Canon 1d, but i dont know if they use polarizers or UV-Filters, i guess not)

[Swampy]

Pure

You will have an option when you change the levels options to save it as default and it will be there forever and all adjustment dialogs will adhear to your rules. I have .10 in there because it was recommended in some tutorial I saw long ago (could have been in a Kelby or Eisman book). It indicates 10%. Anywhere from 5-10% should be good. (PS understands percentages).