Re: Scanner woes

Don wrote:
On Tue, 30 May 2006 22:44:19 +0100, Alex Wilde
<awilde@xxxxxxxxxxxxxxxxxx> wrote:

However, in practice scanner software editing tools are usually a poor
substitute (i.e. a very limited quick-and-dirty subset) of standalone
external editors like Photoshop. They exist only for marketing reasons
and people for whom that's good enough and they can't justify the cost
of a dedicated editor or wish to spend the extra time.

I understand this, and would rather edit in PS. I won't edit all the
images, just the ones that I want to print, but I thought I might as
well scan them all as best I could, then they can always be edited at a
later date.

Yes, that's the gist of scanning "raw". You get the most out of the
scanner, archive that as your "digital negative" and then work on a
copy i.e. to print or make JPGs for screen viewing, reducing size as
required.

However, since you have the originals, once you get a bigger monitor
or higher resolution printer you can go back and create another print
or JPG to accommodate your new peripherals by making the most of them.

But the biggest benefit of this "digital negative" is that it is
fixed. The original (analog) film will continue to deteriorate and you
can't make a lossless copy. Digital data is frozen in time and you can
make as many lossless copies as you want. Of course, you have to make
sure you refresh and check your archives at regular intervals but
that's another story.

I usually have to convert the images I've edited to 8-bit anyway, but I
leave the original in 14-bit so I can maybe take more advantage of them
if I later get more up to date software. If I'm gonna scan all these
boxes of negatives, I only wanna do it once.

Exactly! That's precisely the point I was making above! Should've read
until the end before replying... ;o)

Basically, I would only use Analog Gain, ICE (if appropriate or
desired) and set gamma to 2.2 (in case of Windows). Strictly speaking
the data from the scanner comes as gamma 1.0 (called "linear gamma")
but since monitors are set to 2.2 there's little point in using 1.0.

While slide film is engineered to reproduce the scene accurately (in
some cases with an intended bias towards saturation), transforming a
negative into an accurate color file takes a little more: profiling.
The simplest profiling will correct for colors being mixed-up instead
of pure (Matrix) , and having different gammas. Sure, in principle, you
can edit gammas in PS. With SelectiveCorrection, you can even correct
for the unwanted response of (say) the blue-sensitive layer to green,
etc... That is 9 possible adjustment parameters. The chances of hitting
the right values by just looking at the screen are slim. Matrix-Gamma
profiling will take care of that for you. Creative editing is somthing
else that should not, imho, be mixed with correcting for the media's
little defects. Then again, you could (having determined the film
profile with appropriate methods) apply the profile in PS. But why not
do that right at the scanning stage?
(Note: to be fair, you can also do it right after scanning, with a
command-line batch procedure using the jpegicc utility).
And, with the technical rendering issues being (mostly) taken care of,
one may go one step further, and tell the scanner software that you
want the white and black points at x% of the histogram, with x
conservatively small (for me white 0.1%, black 1%, you choices may be
different). Now the range of available numerical values is
efficiently used, and, depending on personal judgement, you might
consider that a moderate-compression (quality 90+, or 10 in PS scale)
jpeg is adequate and still robust enough for further creative editing.
One film in 16-bit tiff will fill the better part of a DVD. In
high-quality jpeg, the storage is of order 1/20 of 16-bit tiff.
Do note that I do *not* advocate to give the scanner software *any*
freedom to "interpret" the colors, as in "AutoWhiteBalance" or
"AutoLevels", etc... Just to take care of the repetitive part of image
processing.

Bernard

.

Relevant Pages

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