Question about scanning negatives

On Tue, 23 Sep 2008 14:14:59 -0700 (PDT), Scott W
wrote Re Question about scanning negatives:

On Sep 23, 6:25*am, Archibald wrote:
I'm scanning some of my color negs using a Nikon Coolscan IV (2900
dpi). I'm scanning at 48 bits in the hope of capturing maximum tone
gradations. It seems to work great... only problem is the TIF files
are weighing in at around 65 megs each. There will be several hundred
scans, maybe even a couple of thousand (depending on how long I can
tough it out...) and that's a lot of hard drive space.

So my question is, is there a recommended way to reduce the file size
without losing data that matters?

The scans are roughly 11 megapixels, about the same as with digital
cameras, yet are way bigger than digital camera output. There must be
a lot of unnecessary data in there...
Do a test, save some of your better scans as jpegs at the highest
quality, lowest compression, and see if you can see any real
differences between the jpeg and tiff images.

That's a good suggestion. I would bet that even at a *mid-level* . jpg
quality that you won't be able to see the difference and will reduce
file sizes by at least a factor of 10.

"Archibald" wrote in message
...
I'm scanning some of my color negs using a Nikon Coolscan IV (2900
dpi). I'm scanning at 48 bits in the hope of capturing maximum tone
gradations. It seems to work great... only problem is the TIF files
are weighing in at around 65 megs each. There will be several hundred
scans, maybe even a couple of thousand (depending on how long I can
tough it out...) and that's a lot of hard drive space.

So my question is, is there a recommended way to reduce the file size
without losing data that matters?

The scans are roughly 11 megapixels, about the same as with digital
cameras, yet are way bigger than digital camera output. There must be
a lot of unnecessary data in there...

Archibald


Pay attention and only scan negs that really matter.

--owner of an 8000ED

"Archibald" wrote in message
...
On Tue, 23 Sep 2008 17:16:48 -0400, Alan Browne
wrote:

Archibald wrote:
I'm scanning some of my color negs using a Nikon Coolscan IV (2900
dpi). I'm scanning at 48 bits in the hope of capturing maximum tone
gradations. It seems to work great... only problem is the TIF files
are weighing in at around 65 megs each. There will be several hundred
scans, maybe even a couple of thousand (depending on how long I can
tough it out...) and that's a lot of hard drive space.

So my question is, is there a recommended way to reduce the file size
without losing data that matters?

The Dmax of the scanner is 3.6 (manufacturer claim) indicating:

10^3.6 = 3981 levels per color. That fits into 12 bits (4096), so the
48 bit (16 bits per color) is at least 4 bits/color of waste ... or 12
bits total per pixel that is deep in the noise.

In reality you can throw away at least 1 bit to noise, so it's really 11
bits/color or 33 per pixel. 33/8 * 11.262 Mpix = 46 Mpixels for the
useful information in simple compression. However, the scanner does not
store that way. (Check you Nikon s/w; maybe there is a compressed mode).

However, in photoshop, you can save the TIF compressed. Try that. You
should get about 10% - 20% depending on image content.

If I resave using LZW compression, the file size INCREASES by about
20%.

Archibald


As it's a lossless compression, images with a lot of detail can end up
larger than when they started. Dark images compress best. Alan's advice to
use ZIP compression is good, as is the advice to save most of them as JPEGs,
and only the best as TIFF's. As is my advice to not scan them all. In my
experience, not all of them are worth the time.

Scott W added these comments in the current discussion du jour
....

As far as I know all of the tiff formats as lossless. Of
course you can cut the file size down by truncating to 8
bits/color, and there are not that many scans that show any
benefit from more depth then that anyway.

Yes, they are. The rather large sizes (for the day) of TIFF drove
the JPEG spec many years ago.

Anyway, I don't compress files. *Memory is much cheaper than
my time. Get an external drive (1TB or so) and you'll be
quite happy.

I agree with that, but the other constraint to huge files is seek
and access time on the HDDs, internal or external, as well as the
huge load on the CPU to process high mega pixel files. And, most
apps write their undo data back to disk for safe keeping so that
multiples the uncompressed size on disk as many times as you want
to save undos. My PC is a 2.6GHz AMD and this sort of thing brings
it to its knees. To do much better, I would need at least a quad-
core processor, lots more than the 4 gig of memory I have now and
all new apps to support an O/S that can use this neat stuff.

For those people who insist on keeping huge image files,
because they are worried about loss of detail, it is really a
good idea to also keep a copy of all the images in a much
smaller format. The reason is the smaller versions are going
to be much easier to make multiple backups of. It is all find
and good to have all of your massive images on one huge
external drive, but it also a good idea to have a set that is
compressed to the point where keeping multiple offsite copies
is not too painful.

In many cases more then 95% of the real information in a photo
can be stored in less then 5% of the file size.
Getting 99% of the real information into a file 10% is
normally not a problem

I would likely save the as-scanned version pristine on an external
as you suggest but immediately crop it and reduce to whatever I
wanted the final size to be before I worked on it for the reasons I
cite above. I don't print very many of my car pictures so don't
need ultra large pixel or file sizes to do slide shows.

--
HP, aka Jerry

"Don't say 'can't' when you really mean 'won't'"

Scott W added these comments in the current discussion du jour
....

Some care in needed when compressing film scans, odd things
can happen to the grain, but it sure worth trying and seeing
where artifacts first start to show up. It is a good idea to
zoom in to about 400% to get a good idea of just what if
anything is changing.

This is also true of scanning both prints and photos printed with
half-tone processes, but compression and resizing can also be a
positive thing by actually reducing grain turned into noise in the
digital image.

--
HP, aka Jerry

"Don't say 'can't' when you really mean 'won't'"

Keep in mind that JPEG compression affects spatial resolution very
little. The big effect is in tonal range. So you are not losing much,
if any, spatial resolution.

The only spatial resolution loss is in very low contrast areas where the
compression may combine very close shades of a color.

Keith nuttle wrote:
ta in there...

Archibald

This may not be the way most people would see this but I am working on
scanning a lot of old family pictures. The question I asked when I
started this project was "Is the innate resolution of the pictures worth
maintaining the best high resolution image files for the pictures. (Is
it necessary to maintain a 10 mega pixel images of pictures that are of
1.3 mega pixel quality.)

I decide to keep the files in sizes more inline with the original images
than in files of current capabilities

I scan the pictures to high resolution JPG files that preserve the
resolution of the original pictures and provide economy in storage. Even
after manipulation and resaving the quality of the original 50 to 100
year old photo is maintained.

On Tue, 23 Sep 2008 16:25:58 +0000, Archibald wrote:

I'm scanning some of my color negs using a Nikon Coolscan IV (2900 dpi).
I'm scanning at 48 bits in the hope of capturing maximum tone
gradations. It seems to work great... only problem is the TIF files are
weighing in at around 65 megs each. There will be several hundred scans,
maybe even a couple of thousand (depending on how long I can tough it
out...) and that's a lot of hard drive space.

So my question is, is there a recommended way to reduce the file size
without losing data that matters?

The scans are roughly 11 megapixels, about the same as with digital
cameras, yet are way bigger than digital camera output. There must be a
lot of unnecessary data in there...

Archibald

For starters, you might want to revisit the concept of adequacy. What do
you intend to do with the pictures? If you're looking at making 3x4 foot
posters of every one, then maybe you 'need' 11 mp. If, on the other hand,
you'll be viewing most of them on the computer and print only a dozen or
so, then it would suffice to scan them all in at 1mp and rescan the ones
to print (say 8x10 inches) at 3 or 4mp.

Archibald wrote:
I'm scanning some of my color negs using a Nikon Coolscan IV (2900
dpi). I'm scanning at 48 bits in the hope of capturing maximum tone
gradations.

That is far in excess of the tonal resolution (color depth)
of film. You can reduce that to something more in line with
the properties of film without losing anything.

It seems to work great... only problem is the TIF files
are weighing in at around 65 megs each. There will be several hundred
scans, maybe even a couple of thousand (depending on how long I can
tough it out...) and that's a lot of hard drive space.

So my question is, is there a recommended way to reduce the file size
without losing data that matters?

The scans are roughly 11 megapixels, about the same as with digital
cameras, yet are way bigger than digital camera output. There must be
a lot of unnecessary data in there...

Archibald