Hi John and all,
From: John Hudson <OM4T@xxxxxxxxxxx>
>On the few occasions I raise the in-camera ISO rating to 1600 or beyond to
>capture images, especially of people, in poorly tungsten lit surrounding
the
>images are invariably "noisy".
>
>To what extent can this noise be reduced using Photoshop to give the
>impression that the image was taken with lesser ISO rating?
Since you mention specifically tungsten lit sorrounding... that kind of
light has less blue than other colours, especially red. Of course, WB
setting (either for in-camera JPEG compression, or developed from RAW) will
"correct" this by amplifying the blue signal... at the expense of much more
noise and/or quantization artifacts.
With plain PhotoShop (or other image editing software, like GIMP) you can
see and adjust each colour channel separately. Compare the blue channel of
your noisy pictures to the other channels, you'll check what I say... so, a
possible workaround for this case without using any specific noise reduction
plug-in, is to make a noticeable blur on the blue channel only -- experiment
a bit, but a Gaussian blur of 11 px. radius seems to work for me.
Surprisingly, most detail is well preserved -- if any, the picture may look
like some longitudinal CA, but I find them more pleasant than the blue blobs
everywhere of my high-ISO pictures -- I admit the GF1 is not
state-of-the-art here, though.
Please note that this won't work on daylight WB high ISO pictures... Also, a
80A filter on the lens with the WB setting at daylight will definitely
improve the pictures straight from the camera -- at the severe cost of
almost two stops :-(
Hope this helps,
--
Carlos J. Santisteban Salinas
IES Turaniana (Roquetas de Mar, Almeria)
<http://cjss.sytes.net/>
--
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