Reducing Noise without reducing sharpness

There are some noise reducing softwares on the market such as Noise Ninja 
and Neat Image. I wonder if it is possible to do something similar with 
PP11. ie reduce grain or noise without reducing sharpness. I have tried to 
use the noise reducing filters but notice that they tend to lose shatpness. 
Is there a trick to it by using channels?

Kind Regards

Chris 

On Fri, 6 Jul 2007 22:36:13 +0300, "Chris Nicola"
<chrisnicola@hotmail.com> wrote:

>
>There are some noise reducing softwares on the market such as Noise Ninja 
>and Neat Image. I wonder if it is possible to do something similar with 
>PP11. ie reduce grain or noise without reducing sharpness. I have tried to 
>use the noise reducing filters but notice that they tend to lose shatpness.

>Is there a trick to it by using channels?
>

Re commercial or home-made filters, like any automatic tool you should
never use blindly.  Automatic filters can never interprete content,
they just do mathematical operations. One definite exception for this
type of filter imo - avoid using on hair.  Hair is high-detail
low-contrast and will be over-smoothed in some areas.  Treat
separately from rest of image or as below.  Using the filtered image
directly is fine for non-critical work, especially if you use the
filter's sharpen capability as well.

If I'm using a commercial filter of the type you describe, I make the
smoothed pic a layer on top of the original.  Where I feel the image
has been over-smoothed I used a transparency brush (or clip mask) to
partially or totally remove the smooth layer and show the original
below.

I don't know about channels.  I've read so many times that there is
usually most noise on the blue channel but every image I've checked
shows nothing of the kind - all channels look the same noise-wise.
Having said that, last week I worked on an image that had stripes on
the blue channel!

If you want to smooth in PP you need to create an edge-preserving
smooth filter or sequence.  The basic principle is to detect edges and
mask so that they are not smoothed:

Detect the edges of the image using an existing edge filter (in
Effects) on a duplicate layer.  Make sure the detected lines are bold
enough.

Convert the result into black and white.  May need to be inverted and
contrast adjusted.  This is going to protect the edges so make sure
the result covers the desired edges. It's fairly obvious just looking
at the black and white.  Not enough protection, edges smoothed.  Too
much protection, some noise is also protected.

Convert layer into mask then hide black and white layer.  Invert mask
to select the area to be smoothed.

Create object from mask
Create mask from object

Apply suitable smoothing filter to new object.  Over-smooth ready for
next step

Adjust transparency of smoothed new object manually to give desired
smoothing effect.

Combine smoothed object with background, delete any crap hanging
around.


Once you've got it working manually, create a script or macro - best
to be interactive (looped) for setting edge level and degree of
smoothing.  You can make variants using different smoothing filters.

If you routinely have images of similar type, you can fix the edge
level and smoothing amount and incorporate into a fully automatic
script/macro with no manual intervention.  I've got about 6 variants
that I can select from, normally used for batch processing.

I've posted an illustration of the midpoint of my own interactive
edge-preserving smooth filter at:
http://www.starman-imaging.com/imaging/EPS_Filter.jpg (300Kb)

Starman*