by selecting less than 100% opacity for the history brush and then painting over the
area where you want to reduce the effect of the noise reduction software. I suggest
a low value, say 20%, for the history brush.- Layers. My personal favorite. Duplicate the layer and then run the noise-reduction
software on the bottom layer. Use the eraser tool (select an opacity of about 20%)
with a soft edge to gently rub out those parts of the top layer where noise is intrusive;
or you can even vary the opacity of the entire layer until you are satisfi ed that you
have the balance between noise and detail correct.
Sometimes getting the balance right between noise removal and
detail retention is diffi cult. If you overfi lter an image, the microstocks
will reject it. If you have too much noise in your image, the micro-
stocks will reject it. Talk about being caught between a rock and a
hard place! Using the above tips will help you minimize the risk of
rejection; but, if all else fails, you have to get devious and add noise
to the fi ltered image.
“Whoa!” I hear you murmur. “Add noise? But you just mentioned
that noise is bad!” Strangely, adding some noise can add realism back
to the fi ltered image, if done with care. It is not cheating. All that
matters is that the image looks good to reviewer and buyer alike.
My suggestion is to use a free Photoshop plug-in from Richard
Rosenman called the Grain Generator, available from http://www.richardro-
senman.com. Choose either minimum or standard, setting between 2%
and 7%, and see how the fi nished article looks at 100% on the screen.
It only works on 8-bit images, but you’ll be saving your fi les as 8-bit
JPEGs before submitting them, so that’s no problem. I think you’ll fi nd
that adding a little noise can sometimes have real benefi ts. I have used
this trick quite a few times to good effect, and the images look better
for it, even when printed! Of course, it is better to prevent noise in the
fi rst place, but shooting conditions may not always allow for that.
An alternative to the Rosenman fi lter is to use the noise fi lter in
Adobe Photoshop (Filter > Noise > Add Noise). Select Uniform and
around 5%. I fi nd this is easier to use than the grain fi lter in Photoshop
(Filter > Artistic > Film Grain).
Artifacts
I hate artifacts. They are more trouble than the sort of noise mentioned
in the preceding section. Most often they are the result of compression
applied when saving images in JPEG format.
Figure 5.11 is an example of part of an image with heavy JPEG
artifacts visible. The most common cause of visible JPEG artifacts is
saving a JPEG fi le at a quality setting that is too low. The JPEG fi le
format uses lossy compression. File size is reduced by throwing away
some image data. At the highest-quality settings, the data lost are often
ARTIFACTS 91