Banding of colormodulation with brushtool in PS 7.0

HS
Posted By
Hans_Schuetze
Jul 31, 2004
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448
Replies
19
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Closed
I noticed a rather strange difference when using the brush/ airbrush tool in PS 7.0 vs. PS 6.0: It seems that whenever I´m trying to create a smooth transition from light to dark (respectively from one color to another) in PS 7.0 with the brushtool (with or without the airbrush mode activated), rather obvious banding of the color/tonal values appears, giving the modulation from dark to light a posterized look. The transition is no longer smooth, but appears in steps. This effect becomes increasingly noticeable the darker the color gets that is being applied while repeatedly moving the brush over the same area. In PS 6 that phenomenon was absent, both the brush- and the airbrushtool worked just fine. It seems as if this occurance can be somewhat suppressed by activating the "disturbance" function in the brushes palette (sorry if that was not the right word, I´m using the german version of PS and am not sure if the term is chosen correctly), at the price of giving a somewhat grainy appearance to the modulation

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HS
Hans_Schuetze
Jul 31, 2004
More Info on this problem:

I forgot to add that in PS 7.0 both dithering/ scattering and structure in the brushes palette are switched off!

Hans
P
progress
Jul 31, 2004
are you sure its not a problem of working in something like CYMK?
AS
Ann_Shelbourne
Jul 31, 2004
Try reducing the Flow setting to 50% or less (it affects the way the Brush works even when Airbrush is not selected.
I understand that 50% Flow is equivalent to the way that the Brush worked in earlier versions of Photoshop.

Also try decreasing the Brush Spacing to less than 25%.
TL
Tim_Lookingbill
Jul 31, 2004
What zoomed view % setting are you viewing and what’s the image ppi? How big is the brush size in pixels?

Start with a 300ppi new RGB doc. Create a 100% black swatch and zoom in to 700% or any view that lets you see the individual pixels. Pick a light color like 100% RGB yellow from the swatch palette 50% opacity, 100% flow. Click once in the black swatch at 20 pixel brush size and once more close by but not overlapping at 100 pixel size. Compare the edges of the two spots at the current closeup view and then at reduced zoom levels to see if it changes.

On mine the 100 pixel size shows stairstepping/slight posterization but on the 20 pixel it’s smooth. If this is what you’re talking about, there’s not much you can do because of the 8 bit nature of the graphics card and PS having to spread data evenly across a wide area in the file and translating it to the graphics card. I’ld like to see if this same thing happens in a 16 bit RGB image but the airbrush tool doesn’t work on 16 bit images in PS7. Turning on smoothing in brush palette preference doesn’t make a difference. This same type of banding shows up in the gradient tool as well even when dithering is used.

I don’t have PS 6 so I don’t know if the same holds true. Are they the same between the two PS versions under the same parameters described above?
TL
Tim_Lookingbill
Jul 31, 2004
oops! I didn’t catch Ann’s suggestion. I’m going to try it to see if it changes anything.
TL
Tim_Lookingbill
Jul 31, 2004
Well, I played around with the brush palette prefs and found that adjusting between flow and hardness settings seemed to reduce some of the apparent stepping at 700% view on the 300ppi file.

Spacing pref only affects the spacing between the spots that make up an airbrushed line not the smooth transition of brush edge.

Boy! There sure is a lot of customizing you can do in the brush palette I don’t remember existing in PS 4 and 5.

WOW! Talk about a tweaker’s paradise! 8)
AS
Ann_Shelbourne
Jul 31, 2004
The CS Brush palette is spelunker’s heaven.

Just try playing with the Dynamics tabs: Shape, Color, and Other for starters.

If you are not yet using a tablet, this is surely the moment to get one.
MO
Mike_Ornellas
Aug 1, 2004
There is a bug in PS 7 that I showed Mark H. personally with respect to this issue.

The fix is to upgrade to PS 8.

Not sure if 7.0.1 fixed it.
TL
Tim_Lookingbill
Aug 1, 2004
Is this in reference to what I’ve posted or Hans? Or are ours both the same?

And I have PS 7.01.
TL
Tim_Lookingbill
Aug 2, 2004
Fixed the airbrush feathered edge stairstepping appearance against dark background problem.

Here’s what I did:

System: Pismo Powerbook, OS 9.2.2, Virtual Memory on, PS 7.0.1 US Prepress defaults, 19" Princeton EO90 CRT with Apple’s canned sRGB profile as system monitor profile.

Fixed it by fiddling around haphazardly with the color settings and restarting PS that caused something to kick-in somewhere, so forgive my lengthy retracing of steps:

1). With PS open with no docs, checked the "Blend RGB Colors Using Gamma" set to 1.0 in Color Settings.

2). Quit and restarted PS and created new 300ppi RGB doc as before with black swatch patch. Set airbrush to 100pixels, 100% opacity and flow, foreground color to a light color. Zoom view at 400%. Clicked and held down mouse for a fully filled spot and did a second one click spot. Stairstep showed up and oddly when creating the spots straddling the edge of the black patch and white background, the portion of the spot on the swatch was bigger than on the white no matter how long I held the mouse down.

3). Went back into color settings without a restart of PS and turned off the Blend RGB using gamma with 1.0 selected by switching back to US Prepress defaults which turned it off.

4). Did the same two kinds of spots in the same doc and I got smooth nonstairstepping edges and the odd spot shape coverage over the swatch edge behavior went away. Now the spots form a nice round circle straddling the edge of the black swatch and white background. Adjusting flow and opacity either way from each other didn’t induce any changes in smoothness.

An added note, in a previous session yesterday, I had turned on dither in the Gradient tool Option box. It didn’t change anything in this session but thought I’ld include it just to cover all bases.

I am now looking at two differently smooth edged airbrush spots within the same doc after saving it to TIFF and reopening. Some are stairstepped and others are smooth. It now stays smooth when I restart and create a new RGB doc in PS set to US Prepress defaults.

It seems it IS a preference bug in color settings that kicks-in or fixes itself with turning on/off Blend RGB Using Gamma selection.
AS
Ann_Shelbourne
Aug 2, 2004
Tim, try this:

Make an 8-bit 300 ppi document with a light colored background.

Set the Brush palette to:
"Other Dynamics"/Opacity/Fade (Jitter at 0%).
All other Brush palette Options UNchecked. (Smoothing doesn’t make any difference). Default Black and white colors.

Then click and Shift click to draw a fading stroke of paint.

Do this with Flow set at 50% and at 100% and both with Airbrush and with the ordinary Brush.

Zoom in to 100%.

On my machine, a G5 running CS on 10.3.4, I see definite "stepping" (with either brush) when Flow is set at 100% but I get smooth strokes when Flow is at 50%.
TL
Tim_Lookingbill
Aug 2, 2004
Ann,

Did as you instructed. I don’t know if we’re talking about the same description of stairstepping. I get faint ringlets as if the stroke is made of a tightly wound spring laid flat. Setting flow to 100% seems to accentuate the ringlet edges at your settings.
I take it this is what you’re talking about. Sampling with the cursor definately shows it’s in the data according to the info palette, not just the preview.

If I adjust the fade number up from the default 25 to 200 and spacing under Brush Tip Shape to 3% and hardness set to 50%, it seems to reduce it considerably at the expense of hard drive chatter and slowed cursor response probably indicating the calculations involved in adding extra smoothing levels.

What I’m talking about on mine is comparitively minor to your issue and has to be seen at 400% or greater zoom view. It concerns the smoothness of edge transition fade to background around the entire edge of the stroke or spot.

I have a feeling what you’re seeing on your system is a combination of both our issues, maybe.
AS
Ann_Shelbourne
Aug 3, 2004
It was indeed the ringlets which I was talking about. I assumed that it was something like that which was troubling Hans.

You will also see the ringlets if you are using Color Dynamics to fade from a foreground to a background color. (Try fading from Black to white over a pink background.)

I was using an ultra-soft soft brush (0% Hardness)—a harder brush makes the ringlets even more apparent.
Cutting Flow back to 50% and decreasing spacing definitely smooths out the ringlets when using a soft brush but nothing helps with a hard brush.

The edges are very much affected too: the stroke looks like a string of beads—particularly with harder brushes.

You can’t really judge this except at 100% because, at other viewing percentages, interpolation comes into play so you are not seeing a true representation of what is actually being painted.
AS
Ann_Shelbourne
Aug 3, 2004
Do you really want to see the ringlets?

Just paint the strokes on a transparent layer and add a Layer-style Emboss.

Wowee!
DK
Doug_Katz
Aug 3, 2004
Hey, where’s the setting for an "ultra-soft" brush? Can I get a mega-soft one too? How ’bout an über-soft one? I expect these would be useful, not just for painting, but for tickling toes too, huh?
HS
Hans_Schuetze
Aug 3, 2004
Hi and thanks to all for your input!

Maybe I should have given more backgroundinformation: The brushes I´m using had soft edges since I attempted to create a modulation between colors. And I only use the RGB mode when painting. But as far as CMYK is concerned: Much earlier I noticed a somewhat similar phenomenon in older PS-versions when converting an RGB-image into CMYK: In some areas of the image one could see banding similar to what I´m experiencing now, just not as obvious.

Tried some of the suggestions, unfortunately to no avail: Changing the colorspace (in RGB mode) didn´t help, also reducing flow to 50% (or any other percentage) produced the same problem. It just delays the moment when the described banding appears. Like I said, the darker you get with a chosen color (especially when the multiply mode is selected) the more obvious this phenomenon becomes.

Somebody mentioned that this issue has been adressed already and supposedly has been changed in Photoshop 8.0. Assuming PS 8 means PS CS (please correct if I´m wrong): I tried PS CS at my appledealer, and the same problem occured there as well.

As of now, all I can do is use PS 6.0 when it comes to painting with softedged brushes. Maybe this will be fixed in later PS-Versions.

Once again, thank you for your help! Should I come up with a solution I´ll post it here!
TL
Tim_Lookingbill
Aug 3, 2004
So is this ringlet appearance a feature or just a default setting Adobe thought would be useful?

It seems reducing the ringlets could be further diminished if one could change the tonal role-off edge shape of the brush head. But I guess we did that with fade level, hardness and spacing. Has anyone discovered any other hidden pref that could affect this?

Oh well. A tweaking I will go. 🙂
HS
Hans_Schuetze
Aug 3, 2004
Hi Tim,

pretty sure it wasn´t intended, because it just looks bad…..

Your idea of being able to change the tonal roll-off edge of the brush has some appeal, though, since I get the impression that this kind of banding might stem from there. But I might be wrong. I just wish there was a way to get rid of it….
AS
Ann_Shelbourne
Aug 3, 2004
Brushes paint Spots. That is the problem.

A high-opacity brush, even with 0% hardness, still has to fade the color from full density in the center of the paint-spot to zero color at the edge.

For ultimate smoothness, you just have to use multiple strokes of large, soft brushes that are set for reduced opacity and reduced flow.

If you do that, you won’t get the ringlets.

[Hans: My tests were done on Photoshop CS which is version 8.]

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