Along with Moose's analogy, I was thinking about cooking. One reason why
recipes only get you in the neighborhood is because of the slight
variations in source foods, temperature, humidity and ambient odors. For
those of us who use salt, we add varying degrees of salt based on the
nuances of the above. Also, there is the factor of tasting and how a
person's own chemistry changes and the preference for saltiness changes
from hour to hour.
One of the best excercises I've ever done for myself in regards to image
resizing and sharpening was making up a test image of converging lines. I
was always struggling with nasty artifacts and sawtooth edges on resized
images. Lines in the images would get various aliasing patterns. So, I
built an image that had converging black and white lines (later changed to
colors for other tests) and worked it until my resized (downsized for web
display) image looked correct. I ended up needing to blur the image first
BEFORE resizing. I applied an anti-aliasing filter over the image with a
pixel-spread and density which scaled to the final image-size. The greater
the shrinking, the greater the spread. After the image is resized, I apply
a two to three pass sharpening method.
I mention this because these settings I use do get me in the neighborhood,
but no two images will be able to use the same settings. Under ideal
conditions and with an image of known sharpness (perfectly sharp edges in
my lines), the methodology worked well. But if the image isn't quite as
razer-sharp, different settings are needed--especially in the sharpening.
Also, if there is a lot of smudgy patterns (OOF grass, for instance), the
method must be adapted otherwise the blotches get really blotchy. Images
taken with the 35-80/2.8 on the E-1, for example, need different processing
than images taken with the 35/2.8--even at the same settings.
The salt and pepper shakers on the dining room table are there for a
reason. Don't be afraid to add a shake when you need it.
AG
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