Tim,

The amount of disk space a scanned image requires is a function of both the
dimensions of the scan, the resolution of the scan (i.e. the number of dots
per inch) and how many colors the scan uses.

When all other factors are held constant, a 16 grey scale image will be a
lot smaller than a thousands of colors image.

You have to make some decisions on how the image will be used.  If the
scanned image potentially replaces a chemical print, then you need very
high resolution scans, on the order of 40-50 mb minimum for a black and
white image.  On the other hand, if the images are to be used in a catalog
to show what you have, then a 4 X 5 inch image at 65 dpi in grey scale may
be sufficient.  That image may be around 150 kb.

The number of images you can squeeze onto a CD-ROM will depend again on all
of the above factors.

We are scanning some of our historic photographs (grey scale) so that the
scans are roughly 8 inches by 10 inches and 100 dpi.  These images are
about 800kb each, which means we can easily fit them on a floppy disk.
And... remember that an 8X10 at 100 dpi is equivalent to a 4X5 at 200
dpi...also  weighing in at 800k.

These images will be used in on-line catalogs, CD-ROMs and the Internet.
They are probably also of sufficient resolution to meet the needs of most
researchers.  However, they are NOT high enough resolution to replace
chemical prints.

So, we could fit roughly 1000 of our images onto a 1 gb storage medium.  To
find out how many you could fit on a CD-ROM, just check the storage
capacity (which I don't know off hand).

Jim

>Help!
>
>My institution is considering switching to digital photography for
>collections records, but we're having trouble finding out how much disk
>space a scanned image will require.  We cannot deal with the one image
>per one 3.5" floppy disk that one saleman told me (10,000 disks for
>10,000 items?  Surely not?).  I don't think we will need the highest
>resolution scans for reference images, but how high of resolution should
>we consider, and how many bytes will they take up?  Do black and white
>images require significantly less space, or is there much difference?
>
>If we purchase a CD write drive, is there an approximate number of images
>we might hope to store per CD?
>
>Any advice given on or off list would be greatly
>appreciated!
>
>
>Thanks!
>
>Tim Talbott
>Curator of History, Early American Museum
>[log in to unmask]

Jim Angus
Internet and Hypermedia Programs
Natural History Museum of Los Angeles County
900 Exposition Blvd.
Los Angeles, CA  90007

voice:  213/744-3317
fax:    213/746-2999
eMail:  [log in to unmask] = [log in to unmask]
        [log in to unmask]
        [log in to unmask]
        [log in to unmask]