Banding when using any blur tool in photoshop

[dv8or]

I am having some serious issues with banding being introduced to an image when using blur tools in photoshop cs3. I am working on blurring an entire image of a model against a black background. Does anyone have any idea how this can be avoided?
Help appreciated.
Marc

[mushmush]

Hello Marc,
I don't usually use the blue tool itself.
I tend to select an area I want blurred- lasso or quick mask to select-
- cut and paste- then blur that layer- it seems to give me a little more control. You can also erase the areas of that layer if they bleed over an area you want left alone.
As far as the banding::: a 16 bit file converted to an 8 bit file may help - not sure why but it seems to.http://www.retouchpro.com/forums/ima.../surprised.gif

At some point the blur actually begins to become counter productive- it begins to increase the banding.
View the individual channels - looking for a smoother gradient in one channel-
this can be used in channel mixer- maybe set to Luminosity mode.
In extreme cases I've used a duplicate layer used a good deal of "add noise"- then faded that to about 2-3% opacity.- I hope this helps

[mushmush]

Oh Yeah- and try converting to LAB color space- might help too

[namphoto]

first off I'm assuming you mean banding in terms of rough gradient or color transitions. What are your intentions, I don't know of very many if any retouchers who use the actual blend tool itself. If you're trying to just blend a subject against a black back ground, it seems much more appropriate to do so by having a strong cutout with no matting around the image at all then you can mess with your selections and feather if you want that soft transition from front to back, though it'd just be easier if you told us what you wanted to do..

As far as 8 bit vs 16 bit you have it wrong mushmush, downsampling an image from 16 to 8 would not help an images rough banding problems as decreasing the color depth would decrease the colors that are needed in between a transition to make it smoother.


Ok so I know this is long but if you're talking about banding in another term as in the weird stripes you get between a light and dark area with a quick gradient transition, or quick blurring, that's pretty much natural. It's called mach banding.

[Quantum3]

2 parameters causes the banding:

1) The bit of depth of your image (you have to work in 16 bpc).
2) Your monitor (unless you have an Eizo 16bpc).

Note that the banding will not appear when you print out the image.

[dv8or]

Thanks for the response - sorry for my tardy acknowledgement...
I have tried a variety of ways of selective blurring but unfortuately the areas I need to blur are the problem areas blurring. Adding noise does seem to help the image but the tradeoff is the noise. I will try the conversion to 8bit and see if that helps...
Marc

Originally Posted by mushmush

Hello Marc,
I don't usually use the blue tool itself.
I tend to select an area I want blurred- lasso or quick mask to select-
- cut and paste- then blur that layer- it seems to give me a little more control. You can also erase the areas of that layer if they bleed over an area you want left alone.
As far as the banding::: a 16 bit file converted to an 8 bit file may help - not sure why but it seems to.http://www.retouchpro.com/forums/ima.../surprised.gif

At some point the blur actually begins to become counter productive- it begins to increase the banding.
View the individual channels - looking for a smoother gradient in one channel-
this can be used in channel mixer- maybe set to Luminosity mode.
In extreme cases I've used a duplicate layer used a good deal of "add noise"- then faded that to about 2-3% opacity.- I hope this helps

[dv8or]

Thanks for the reply - I was not very clear about what I am trying to achieve. I am purposefully trying to introduce blur to replicate an image taken out of focus so need to blur the whole image. The banding is occuring as a result of the blur no matter what tool i use. Adding noise before blurring does help but is not ideal. The "Mach" banding is exactly what I am talking about...
Marc

Originally Posted by namphoto

first off I'm assuming you mean banding in terms of rough gradient or color transitions. What are your intentions, I don't know of very many if any retouchers who use the actual blend tool itself. If you're trying to just blend a subject against a black back ground, it seems much more appropriate to do so by having a strong cutout with no matting around the image at all then you can mess with your selections and feather if you want that soft transition from front to back, though it'd just be easier if you told us what you wanted to do..

As far as 8 bit vs 16 bit you have it wrong mushmush, downsampling an image from 16 to 8 would not help an images rough banding problems as decreasing the color depth would decrease the colors that are needed in between a transition to make it smoother.


Ok so I know this is long but if you're talking about banding in another term as in the weird stripes you get between a light and dark area with a quick gradient transition, or quick blurring, that's pretty much natural. It's called mach banding.

[dv8or]

Thanks for that - I am working in 16 bit mode with an apple 20" display which is calibrated. Unfortunately the banding on screen does show up in print and that is what my issue is I am afraid. Any thoughts?
Marc

Originally Posted by Quantum3

2 parameters causes the banding:

1) The bit of depth of your image (you have to work in 16 bpc).
2) Your monitor (unless you have an Eizo 16bpc).

Note that the banding will not appear when you print out the image.