measekite wrote in news:mEale.1684$rY6.1596
@newssvr13.news.prodigy.com:

When you reduce the effect of noise in a program like photoshop

1. How effective is it in reducing noise?
2. What are the undesireable things it does when noise it reduced?

I would say that the effectiveness of noise reduction varies from image
to image. For example, if the main subject is reasonably well
illuminated, its intrinsic noise levels will likely be low. If the
background is darker, then that's where the noise is likely to show up.
If the background is out-of-focus, then applying noise reduction to it
will not disturb much detail, so the noise reduction will be fairly
"invisible" but effective. If the entire image is noisy, then it may
fundamentally already have less detail as a result of the noise. Hence,
applying noise reduction may reduce the details even further, and also
affect the tonal transitions, to make the end result look a bit
"plasticky". To some degree, the undesirable effects of noise reduction
are a subjective assessment that depends on the print size and the image
quality desired by the photographer.

It may be instructive to investigate the effects of noise reduction on
images for yourself. That way you can readily gain some first hand
experience. There are a number of demo or freeware versions of noise
reduction software that can be installed on your computer. Then, it is
possible to download some images from the digicam review sites that have
specifically been taken with varying ISO values and therefore varying
degrees of noise present. Apply the the noise reduction and see what you
get, and you should then be able to reach a judgement as to how important
noise might be for your purposes.

Keep in mind that using a ZLR at ISO 200 or ISO 400 will result in images
that are quite a bit noisier than those from a DSLR at the same or even
higher ISOs.

--
Witold.