At 09:59 AM 6/3/2001 -0500, Tom Scales (in response to a request for
post-processing information from Alan) wrote:
>I would say it is two things:
>
>1) I usually apply a small amount of 'unsharp mask' (Don't ask me why
>unsharp means sharpen). That really makes the details jump out.
Actually, the term originally comes from darkroom work, where a copy of the
negative was made that was slightly blurry, and was then used as a "mask"
against the original. I've never tried this technique in the darkroom (and
probably never will, now that I have a more flexible and less smelly "digital
darkroom").
In digital terms, "Unsharp Mask" creates a slightly-blurred negative image
(using Gaussian blur) of the image you're trying to sharpen, and then uses
"compare and contrast" algorithms (plus some custom tweaking by the user) to
produce averages and enhance differences in such a way that the original image
looks sharper. According to the book "Photoshop in a Nutshell" (2nd edition),
p. 363, "The [duplicate] image is never visible, but is used as a mask that
protects and exposes certain areas of the [original] image. ... The
differences between the two images determine the amount of sharpening applied
to each pixel in the image. The greatest amount of sharpening occurs where the
two images are most different. Little sharpening occurs in areas that are most
similar."
>2) I'm using a Polaroid Sprintscan 4000. The difference between 2700dpi and
>4000dpi is most obvious in details like this.
There's no substitute for having huge amounts of detail in the original image,
that's for sure. The closer your DPI/LPI gets to the theoretical resolution of
the film + lens combination, the better off you are when you need to do
post-processing.
Also, don't forget to save the original image in some "lossless" format (the
most frequently-offered one in scanning software that I know of is uncompressed
TIFF [or TIFF with lossless compression]), and then work with a copy of that.
[snip]
>> Btw I am sure I am doing something wrong because Tom's picture of flowers
>> have a lot more micro detail on the flowers. Hum.... Tom ???
Get closer. Seriously. If your scanner's not up to extracting huge amounts of
detail, give it more sheer area from the print or negative to work with.
And don't be afraid to experiment lots. Some pictures I dick with for up to an
hour, until I get something I can live with. It's not cheating -- all the
greats did lots of darkroom work to achieve similar results. This is just
"electronic darkroom work."
Good luck.
Garth
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