- How to use noise
- in computer art and photo-retouching
D'Lynn Waldron, PhD.
- .
Noise is a very important filter for the computer artist and photo retoucher.
- .
- A- Noise Can Be Used To:
- - 1 Simulate and replace film grain
- 2 Add a natural sparkle to skin
- 3 Prevent gradients from banding when printed
- 4 Break up blocked shadows and blown highlights
- 5 Prepare a surface on which to apply texture filters
.
- B- Noise Controls:
 Various noise filters come with one or more of these controls.
Their effects can be seen in the filter preview window.
Grain size: which should be adjusted to match that of the film or be appropriate
to the scale of artwork.
Grain density: which should be adjusted match that of the film or be appropriate
to the artwork.
Grain color:
__ Multi-color is used for most full color images and
adding sparkle to skin. The grain of color film is multi-color.
__ Monochromatic is used for grayscale and toned images
to avoid adding unwanted speckles of color.
__ Selective hue is available in some third party filters
and can be used for any of the above.
Grain distribution:
* Normal or Even distribution gives
a mechanical appearance and is less visible than Gaussian.
* Gaussian gives a more clumped appearance
that is more visible and more closely resembles the clumping found in film grain.
Grain blur
* Grain may need to be blurred in another
filter to match that of the film, or to otherwise make it more suitable to the image,
such as skin tones.
* Try various blur filters, including
Gaussian, to soften noise.
.
- C- Preparing To Apply Noise
- 1 Save a copy of the base image without any noise.
2 Make two layer copies of the base image.
3 Activate the top layer copy to apply noise to it.
.
- D- Applying And Adjusting Noise
- 1 Apply noise to the top layer copy.
2 Use the Noise Filter preview window to select the appropriate
__ size, density, color, and distribution.
3 Use blur if needed on the applied noise.
4 Adjust the transparency of the layer with noise.
5 Selectively fully and partially erase areas of noise.
6 Duplicate noise layer and turn off the eye to make it invisible.
7 Merge the visible noise layer with the copy of the base layer under it.
8 Save all the layers as a Photoshop file.
9 Separately save the Merged layer only, as a flattened
__ IBM TIF file, LZW lossless compression
This universal format can be read by both Mac Photoshop and IBM
.
- E- Using Noise To Simulate And Replace Film Grain
- __ When an image is drawn in the computer, or when
a photograph is retouched, the result is a smooth, plastic look.
__ The steps above to simulate and replace film grain.
__ Remember to consider using additional filters to
adjust blur, or contrast, hue, transparency, etc.
.
- F- Using Noise To Add A Natural Sparkle To Skin
- - If you look at anyone's skin that is not covered with heavy make-up, you will
see that it is actually a myriad of tiny colors, as the Impressionists have show
us.
- Computer painted skin has a plastic look, which adding noise will take away.
- The size. distribution and color, as discussed above should be appropriate to the
image.
- Remember to consider using additional filters to adjust blur, or contrast, hue,
transparency, etc.
- Some parts of the face should have little or no skin grain, and to accomplish this
you selectively erase in the layer to which you have applied the grain. Completely
erase over the eyeballs, partially over the lips, and usually some or all over the
hair.
.
- G- Using Noise To Prevent Banding In Gradients
- - Many printing processes will create banding in computer generated gradients
because they are not able to precisely match all the colors.
- Adding grain will reduce or eliminate banding in computer generated gradients when
they are printed.
- Blurring can reduce any speckled look.
.
- H- Using Noise To Eliminate Blocking In Highlights
- - Areas with no color at all, print as white paper and in photo-realistic imaging
this gives a blown-out appearance to those areas.
- Putting some noise into totally white areas in photo realistic and other images
where pure paper is not wanted, will improve the look of the printed image.
- Because the grain filter will not work in white, you will have to create a very
slightly toned layer for this, and then carefully erase to the area you want then
adjust transparency, contrast and blurring.
.
- I- Using Noise To Eliminate Blocking In Shadows
- - Except where solid color is wanted for some graphics, a solid block of color
looks unnatural and can be ugly in a print. This is particularly true in shadows
in hair and on skin. The very judicious addition of noise can improve this.
- Remember to consider using additional filters to adjust blur, or contrast, hue,
transparency, etc.
.
- J- Using Noise To Prepare For Texturizing
- - Many texture filters do not work properly, or at all, on a perfectly flat color.
- Using the steps above you can add grain to the area to be texturized so the filter
has something to work on.
by D'Lynn Waldron, PhD.
©2001 www.dlynnwaldron.com
Winner of the Millennium Golden Crane Award for lessons in the graphic arts.
The Design Center and Photoshop Tips & Tricks sends out a warm thanks to D'lynn
for her continued support with great content for Design Center readers. If you have
a technique to share, just let us know!
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