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Guest
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 Posted:
Wed Dec 22, 2004 7:24 pm Post subject:
Re: Adjustments in TWAIN vs PaintShop Pro? |
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Don wrote:
| Quote: |
On Mon, 20 Dec 2004 15:08:36 GMT, DavidTT@att.net wrote:
Don, it seems like we are back to discussing raw scan again <g>.
It's hard to beat the advantages of a raw scan! ;o)
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Right, and a topic seldom addressed in books and online tutorials.
That's why I suggested drafting a raw scan faq for this group a while
back, but never got around to it. |
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Guest
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| Posted:
Wed Dec 22, 2004 7:32 pm Post subject:
Re: Adjustments in TWAIN vs PaintShop Pro? |
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Don wrote:
| Quote: |
On Mon, 20 Dec 2004 08:50:00 -0800, "Mark" <nospam@thanksanyway.org
wrote:
However, tonal (dynamic) range can be
improved by, for example, scanning twice - once for highlights and
once for shadows - or simply tailoring the range to the part of the
image where the object of interest is.
Can you direct me to a tutorial that describes the process
of multiple-pass scanning for highlights and shadows?
That idea is new to me. It sounds intriguing.
The procedure is generally known as "(digital) contrast masking" so if
you google for that you'll get quite a few hits. I'm not aware of a
tutorial as such because I did it the hard way, but I'm sure there is
one somewhere. Maybe someone else can chime in...?
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[snip]
| Quote: | The basics are as follows (again, please ignore if you know this):
The dynamic range of a scanner (i.e. the ability to expose both bright
and dark areas equally well) is often insufficient. The result of this
is that if you expose for highlights the shadow areas are a
featureless dark mess. Conversely, if you then boost exposure to bring
out the detail in shadows, the bright areas are all "burnt out" and
become a featureless white.
The idea is, therefore, to scan twice. Once, tailoring exposure to get
the most out of shadows, and then scan again but tailoring exposure to
get the most out of highlights. After that the two scans are combined
resulting in an image with equally well exposed dark and bright areas.
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Or, shoot the same image multiple times on a tripod, each time with a
different exposure. Then select and scan two (or more) frames to combine
in PS.
| Quote: | Well, that's the theory... ;o) In practice the first problem is
alignment of the two scans. Depending on how picky you are, you may
want or need to do subpixel alignment (i.e. move one image a fraction
of a pixel).
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For me, this is *the* most difficult part of the process. The tutorials
are mostly for two exposures captured on digital cameras. These captures
are easier to align in PS since there is no scanner misalignment
involved. |
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Don
Guest
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| Posted:
Thu Dec 23, 2004 10:20 pm Post subject:
Re: Adjustments in TWAIN vs PaintShop Pro? |
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On Wed, 22 Dec 2004 14:24:34 GMT, DavidTT@att.net wrote:
| Quote: | On Mon, 20 Dec 2004 15:08:36 GMT, DavidTT@att.net wrote:
Don, it seems like we are back to discussing raw scan again <g>.
It's hard to beat the advantages of a raw scan! ;o)
Right, and a topic seldom addressed in books and online tutorials.
That's why I suggested drafting a raw scan faq for this group a while
back, but never got around to it.
|
The main problem (for me at least) is time. I'm sure there's a lot of
good info in these threads but it takes to time to consolidate them...
:-(
It is interesting, though, how "natural" the concept of raw scans
seems. A large percentage of people who get into scanning
instinctively want to scan raw even though they may not even know what
to call it.
Don. |
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Don
Guest
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| Posted:
Thu Dec 23, 2004 10:20 pm Post subject:
Re: Adjustments in TWAIN vs PaintShop Pro? |
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On Wed, 22 Dec 2004 14:32:19 GMT, DavidTT@att.net wrote:
| Quote: | Well, that's the theory... ;o) In practice the first problem is
alignment of the two scans. Depending on how picky you are, you may
want or need to do subpixel alignment (i.e. move one image a fraction
of a pixel).
For me, this is *the* most difficult part of the process. The tutorials
are mostly for two exposures captured on digital cameras. These captures
are easier to align in PS since there is no scanner misalignment
involved.
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Did you catch my message on how I go about sub-pixel alignment in
Photoshop (although other software can be used also)? If you haven't
I'll search my archives and dig it up.
Even though sub-pixel alignment causes a very slight blurring it
basically solved the alignment problem for me. I "move" the image
which contains less data. Currently, that's the shadows and a slight
blurring there is not even noticeable. The only thing is that the
whole process, including combining the images afterwards, is time
consuming...
Don. |
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