Re: Sharpness in Tiff Scans
- From: Raphael Bustin <rafeb@xxxxxxxxxxxxx>
- Date: Sun, 01 Jun 2008 16:16:47 -0400
On Sun, 01 Jun 2008 06:28:55 -0500, Mike Fox <mikefox@xxxxxxxxx>
wrote:
0
Even the sharpest film images don't look all that great in
4000 dpi scans. As others have pointed out; the higher
the resolution, the uglier the scan will look. IMO, film
tops out at around 2500-3000 spi "equivalent" and
anything much beyond that is overkill.
(There may be occasional detail above this limit, but
it is quite rare...)
Here's a page full of scan samples at full resolution with
which to compare your own scans.
http://www.terrapinphoto.com/jmdavis/
You may find it interesting.
I agree with others that JPG vs. TIF is entirely
irrelevant, so long as JPG compression is held to
reasonable levels.
rafe b
www.terrapinphoto.com
I went to your page of scan samples--very impressive. You've done a
great deal of research and are knowledgealbe far beyond myself. If
you would, I'd appreciate your thoughts on several questions.
I'm archiving my family's history in 35 mm slides by scanning them and
putting them on DVDs. I want to leave for my children's children a
pictorial history of their ancestors. And of course, I want the best
quality pictures for them. That's the question--how to achieve the
best for a 100 years in the future!
I've started with a Nikon film scanner at 4000 dpi and 16 bit color
in TIFF. I only crop, balance faded colors, and filter to remove
dust. It seems to me that appling filters to sharpen, remove noise,
etc only adds artifacts to the image that block future generations
and their improved technology to produce a better images. Should I
just leave a 'raw' image for the future or make the best looking
picture now? Does 'dust removal' do any damage?
Of course, 4000 dpi and 16 bit color in TIFF on a 35 mm make a 100 MB
file. I'm not happy with that, but if that's what it takes, so be it.
But you say that's overdoing it, that 3000 dpi fully exploites all the
information in the image. I believe in the future, images will be
viewed more and more on screens; and thinking back, I see consequences
for limiting the dpi. When monitor screens were 640 x 480, an 800 x
600 image would overflow the screen. On today's monitors, it's
looking pretty small. For the distant future, shouldn't we try to for
as many dpi as possible even if the software is just interpolating
between the film grain? Doesn't upsizing an image really degrade it?
Does 16 bit color provide real value in my scheme? I can see your
point on JPEG vs TIFF. I'll save just once before burning to a DVD
and won't be getting repeated save degradation. What is a
'reasonable' JPEG compression?
Thanks
Mike Fox
Wow, lots of questions.
You have to decide for yourself whether to compress the images
or not, and what resolution to use. The resolution you "need"
depends on what you plan to do with the images. For large
prints, you always want lots of pixels. For viewing on a
monitor, not nearly so much. (see www.scantips.com)
Or you have to make a more fundamental decision: pick and
choose which images deserve your best efforts (scan time,
Photoshop time, and storage media costs...) Scanning
a lifetime's worth of images is a daunting task.
Storage media is cheap these days --- but you ALWAYS need
to have backups, preferably more than one backup set.
There have been many discussions over the years about the
value of 8-bit vs. 16-bit color. For the last few years I've
decided to go with16-bit because media costs are low
and processing power is plentiful. The benefits aren't
entirely clear, but hey, it's the "safe" option, sort of...
The "old" thinking went this way: 8 bits per color is fine,
so long as you start with a good scan and so long as your
image doesn't need radical color fixups. If you find yourself
pushing really hard on the controls in Photoshop to get the
colors or gamma right, stick with 16-bit. On the other hand, if
they look good right off the scanner, then 8 bits will do.
The extra bits give you "room to maneuver" in terms of
color and gamma shifts. That's the main benefit.
I think digital ICE is the best thing that ever happened to
film scanning, and use it roughly 100% of the time. At least
in the normal setting, I cannot detect any loss of detail or
resolution from having it on. It's as close to magic as
digital imaging gets.
As for JPG storage (vs TIF) -- it's appropriate for an
image in its final form -- but should be avoided for
any image that's still a "work in progress." It's the
saving-to-JPG step that loses information.
Experiment with and understand JPG compression
levels. Bottom line, JPG can cut file sizes typcially
by 75% or so before visible artifacts become
apparent.
rafe b
www.terrapinphoto.com
.
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