Archival Image Storage
with Digital Technology
The following is a conversation
from the Sito Mail List regarding digital storage of images.
Hi fellow sitiods
Question. I am working on
archival stuff in my studio. Does anyone know
the low down on digitally
storing images from scans. what is the best
dpi for quality and economy.
In short. If I am scanning images of art
and I want to be sure they
are viable from a reproduction standpoint,
what is the best solution?
Cecil
Hey Cecil,
On your question, I would
use 300 dpi.
Small World: Today in my
Drawing II class a student of mine,
Gabriel Sheets, asked if
I knew you. Seems you and his parents
are old friends. I come
down to my office to check for mail
and there's this email from
you.
Bob (Anderson)
Bob Anderson - bazooka@mail.utexas.edu
University of Texas at Austin
Department of Art & Art History
Senior Lecturer, Studio Division
ART 1.208, 512-471-0913
Austin, TX 78712-1104
Regarding digital storage
of images from scans, I think full 24-bit
color, 300dpi is sufficient
for most painted works (but I'm no
technical expert-- just
have experience). The main idea is method
of reproduction though--
do you intend to reproduce by color
halftoning, or by continuous
color (dye-sub, etc.), or perhaps by
some printing process not
invented yet? And is this digital replica
supposed to stand for the
original?
If you're just planning on
printing half-toned images then 300 may
even be too generous, but
for more sophisticated printing it may be
insufficient. Of course
a 300 dpi, 24-bit color 6"x9" TIF-compressed
(lossless) image would be
about 15-20MB, so 300 may be all you can
afford.
If you're only interested
in scanning line-drawings (black/white--
single bit color), then
1200dpi should be more than sufficient for
any printing process now
and hereafter (assuming intelligent printing).
+j
Jesse Reklaw
weekly dream comic *** submit your dream!
reklaw@nonDairy.com
http://www.nonDairy.com/slow/wave.cgi
nonDairy Publishing
PO Box 200206 New Haven CT 06520-0206
300dpi sounds good so what's
the best way to store those big images? a
zip drive I guess? That
seems like a heck of an expence if you have a
lot of images. Yes I am
hoping to store images in such a way that I can
make use of the copyrights
throught making high quality prints at some
point even if the art is
sold but of course that needs to be as cost
effective as possibe. Would
it be better to photograph the work and scan
after the fact? My collages
fit on the scanner and I can tell an obvious
difference in the quality
of the image compared to a scanned photo. It's
just that I don't want to
have my works all sold and then later kick
myself in the butt because
I didn't get the best reproduction that I
could.
Cecil
So you want to put those
images on tape ehh? How long do you expect your archive to last?
My own experience is that magnetic media degrades over time. If you
need proof, find an old cassette tape and play it. With the price of recordable
CD's approaching affordable, consider that route instead. It's not proven
to be totally archival, but we know they last a lot longer than magnetic
tape, and isn't subject to accidental erasure from outside energy fields.
(unless you melt one! (-: )
My thoughts:
As for the scanned image
matching the original, finding the best scanner
you can lay your hands on
is the answer to that. Using a variety of the "low end" scanners I have
seen a LOT of variance in how the image is handled. I've also seen differences
using the same scanner with different hardware! (found that one outr myself
when my motherboard quit) There are some promising looking slide scanners
on the market, though I haven't tried them. A good slide of your artwork
scanned and then archived to CD would be a good bet. You can also store
the slide in an archival environment and it will last almost as long
as the CD.
The rest of the SITO list is more competent to comment on output, so I'll
leave it to them to comment on file size/type/dpi etc.
-PCS [PETER.C.SMAKULA@monsanto.com]
The rules are...
MORE! ALL THE TIME!
IN EVERY FORMAT CONCEIVABLY
NECESSARY!
SAVE EVERYTHING.
PRAY CONSTANTLY!
Based on nightmare-rush-foul-ups
and the F--- factor frequently encountered in
the art production world,
I scan and store any image in the highest color bit
depth and the highest possible
MAXIMUM resolution.
My limits are set by the
quality of the scanner I am using, and the capacity of
whatever media I am storing
or transporting the image on.
My original scans range between
400 to 1200 DPI which can mean big files but I like the safety net.
My solution for storage has
been Stuffing my ZIP back-ups, then transferring the contents to CDR disk
when I have near 600MB of stuffed files. If you can't
spring for the recorder,
your local service bureau can help. Also I think there
are mail order services
available for boonie bound bit bashers.
Some people like MO but I've
had trouble with that media. Fool me once...
The ONLY time I worry about
how small to make a file is when I am delivering a final file to web or
printer.
Regards Stevenlee
Hello everybody,
As for scans, my philosophy
is to scan with way more resolution than
I need so I have a lot to
work with afterwards. I figure on how much
disk space I want to use,
say 25 MB, and then increase the dpi
resolution until the scan
size will be just under that size. Once I
have cleaned up any "speckles"
and such and am happy with the colors, I
reduce the image to what
will be 600 or 300 dpi when I print it out.
As for image formats I did
some experiments with various images
including scanned photos,
raytraced images, and random noise at various
color depths, converted
them to almost every possible format, and also
tried various compression
packages like PKZIP, compress, gzip to see
which combination would
take up the least file space. I found that
24-bit true color TIFF with
LZW compression took up the least space
without losing any of the
original image data. Second best was gzipped
pbmplus PPM format, and
third RLE encoded SGI RGB images. Your mileage
may vary depending on the
content of your images.
If you don't mind some loss
eg. if your pictures have lots of smooth
gradients and not sharply
contrasting areas, high quality JPEG's get the
best compression, and if
you do ~90% quality the image will be darn near
the original, though I suggest
you check the result before you delete
the original.
If you have line drawings,
or pictures with only a few colors, GIF will
probably give you the best
compression. However, GIF is a 256 color
color-mapped image format
and is very crappy for images with smooth
gradients and/or lots of
colors because your images will be quantized
down to 256 colors.
If you use Floyd- Steinberg error diffusion
dithering, the result may
be palatable, but probably not great for
reproduction. Also
I suggest doing the quantization in YIQ, YUV, or
maybe XYZ colorspace if
possible rather than RGB--those color spaces
more closely approximate
the behavior of our color perception, so the
colors will usually look
more uniform and closer to the original than if
you use RGB. I use
ImageMagick on a linux box to do that.
As for archive media, for
long term storage forget about tapes. If
tapes are your only option,
I suggest you use BRU archive software
because it does a better
job of recovering from damaged media (it uses
some parity bits and checksums
to help "fill-in" lost data). Exabyte
tapes and tapedrives are
pretty good, also HP has some new DAT drives
that are nice. I don't
care for the "Travan" or QIC type tapedrives
like the Seagate or Iomega
drives, I think they're noisy and slow, and
stuff may be stored in some
proprietary format. DLT media may fare much
better in the long run,
but the hardware is a lot more expensive. I
don't know about the durability
of ZIP disks or LS-120, but that's a
puny 100 or 120 MB, and
I wouldn't count on it, as far as I'm concerned
it's already pretty much
obsolete though some people love those things.
Writable CD's are dirt cheap
these days--I just bought a case of 25
Kodak 70-minute CD-R for
$80 on sale at a local computer store. Don't
buy the cheapo noname brands.
If you're running some version of
MS Windows, the IDE CD-R
drives may do fine and some are faster than
the SCSI CD-R's especially
if you also want to use it to read CDROMS.
If you're running linux,
there aren't any drivers for the IDE CD-R's
yet, just for the SCSI,
so you will have to pay a bit more or write your
own drivers, but there's
a pretty nice package called "X-CD-ROAST" for
writing the CD's.
Also count on having at least 650 MB disk space for
mastering the CD, preferably
on a SCSI disk though I've been using
Ultra-IDE and have no problems.
I have an HP 6020i SCSI CD-R on my
linux workstation and it
works great. If you want to mass-produce the
CD's, Kodak makes a 75 and
150 disk CD-R system that looks pretty nice
for a few $1,000's.
As for DVD (4 GB capacity)
I would wait awhile until some stable
standard emerges, else it
could go the way of the beta-max.
--
"Jonathan F. Dill" (jonathan@carb.nist.gov)
http://www.umbi.umd.edu/~dill
Hi
List, interesting discussion.
For my money and if archival
quality is more important than cost, I would
photograph the paintings
with a medium or large format camera using
professional low-contrast
film and from a copy stand or other controlled
lighting environment. Then
I would have a professional grade PhotoCD made in one of the high-end formats
that support higher resolutions. Finally,
I'd keep both the film and
CD under archival conditions until needed.
As far as cost, the above
is more expensive than using consumer grade
stuff, but you should get
a much better set of archival documents. As
others have pointed out,
consumer-grade scanners (and film) can vary
greatly in quality and are
not really optimized for archival purposes--too
high contrast, poor color
dynamic range, color shifts. Photo-copy work is
not too hard to learn, or
if you live near a college with a good art or art
history department, it pretty
easy to find a student who is knowledgable
and willing to do the job
below professional rates.
PhotoCD, especially the higher-end
professional formats, is a really cost
effective way to get high
quality with out having to buy your own
equipment. Use a custom
PhotoCD shop, don't get your PhotoCD made through your local developer
as typically they are contracted with a volume shop that does not optimize
the digitization of each negative or transparency
and you'll often get a color
cast to your images. Again, a custom
shop--especially if you
get the higher-end professional PhotoCD made--is a little more expensive,
but for archival purposes of things that really
matter to you, its the way
to go.
- Dave
Dave Poindexter
Program Director for Computer
Graphics & Design, Keiser College
1700 Halstead Blvd. Bldg.
#2, Tallahassee, FL 32308
phone: 1-850-906-9494;
fax:1-850-906-9497
mailto:poindexter@scri.fsu.edu
"I wasn't expecting the Spanish
Inquisition." --Monty Python
Dave Poindexter wrote:
> For my money and if archival
quality is more important than cost, I would
> photograph the paintings
with a medium or large format camera using
> professional low-contrast
film and from a copy stand or other controlled
> lighting environment.
Then I would have a professional grade PhotoCD made
> in one of the high-end
formats that support higher resolutions. Finally,
> I'd keep both the film
and CD under archival conditions until needed.
Sounds reasonable to me.
Most of my "work" has been raytraced images of
molecule models for scientific
journals--I like the colors to be aesthetic,
but mainly what matters
is good contrast and not so much being able to
reproduce the colors accurately
at a later date.
--
"Jonathan F. Dill" (jonathan@carb.nist.gov)
http://www.umbi.umd.edu/~dill
First of all, get
the best scanner that you can afford. It makes a
huge difference in the quality
of the scanned work. In response to the
question of scan or photograph-and-scan,
I think it would depend on the
media involved. A
pen-and-ink drawing would scan well, but an oil
painting probably would
not.
Second, on the question
of storage, it depends on the amount you are
willing to spend and how
much storage space you're going to need. If
you're looking for the cheapest
solution for a small amount of storage
space, a Zip drive is probably
your answer. If you're willing to
spend a bit more, my suggestions
would be either a CD-RW drive (they're
not that much more than
a standard CD-R and the rewritable media is a
big plus) or a Jaz/Jaz-II
drive. (The Jaz-II is a brand new product
that will store 2GB per
cartridge.) And, of course, DAT tape is also
an option, albeit a somewhat
inconvenient one.
The things that would make
up my mind between the options is 1) short
term cost, 2) long term
cost, 3) storage space required, and 4) length
of storage time. A
Zip drive is certainly the cheapest short-term.
You can pick a drive up
now for about $150. However, they're fairly
slow, they don't store much
per cartridge, and it works out to be
about 10c/MB. Jaz
drives are around $300, and they're much faster.
They're about 8.5c/MB.
CD-RW drives are between $400 and $500 for an
HP quad-speed write (though,
depending on the feature that you want,
you can pay up to $800.)
CD-R media is about 1c/MB, but you also need
to have 650MB of free drive
space in which to master the CD. CD's also
have the longest shelf life
and the lowest failure rate. Also keep
in mind that CD-R's don't
always burn properly the first try. CD-RW
media works out to about
3.2c/MB.
Hope this helps!
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