In a comment in DearMYRTLE's community on G+ I mentioned that we have been offered to take part in a scanning project - 6.000 portrait photos from around 1900.
Scanning should be for archival storage.
600 or 400 dpi, 24 bit color, TIFF-file with LZW-compression is under consideration.
Metadata should be included in the file.
I did some tests with my EPSON V750 PRO scanner and perhaps they could be of use for others.
I plan to do the scan from within my Photoshop CS5 software.
The software which is included with the scanner is EPSON Scan but also Silverfast - a much more capable scanning program.
The EPSON scan program does not support saving with LZW-compression. However this can be done as conversion with programs like freeware IrfanView.
I did scan a sample with the EPSON - one at 400dpi and one at 600dpi.
600dpi >> 46 MB >> 32MB after LZW-compression
400dpi >> 21 MB >> 14MB after LZW-compression
The latter is my preferred method - scans quicker and takes less space on harddrive. For single scans I would choose higher resolution but for so many ....
Next test will be from within the Photoshop*.
I "Import" the file from the scanner.
I can choose to scan with the EPSON program via the WIA-support or via the VueScan-program which I also have installed.
The result is quite similar.
When I have done cropping (if necessary) I do not make any other adjustments unless quality is very bad.
Since I want to include Metadata** I switch to File properties under Archive and can input information from a template and add information particular for this picture.
* Metadata is included "inside" the picture file and ensures that information is kept with the picture. It should be noted that some programs strip the metadata when you make changes (like changing from TIFF to JPG)
Finally I "Save as.." TIFF and tick LZW - lossless compression.
** I did check with an older Photoshop Elements 8.0 and from what I can see all steps can be made with PE.
SOME MORE ...
I could not resist to try two "new" archival formats: JPEG2000 (13 years old!?) and PNG. These formats are suggested by some archival institutions.
JPF (JP2 compatible) >> 8,5MB
PNG >> 10MB
Both formats are non-destructive
However not all programs or browsers support these formats and I am not sure they can include Metadata.
I stick to the old faithful TIFF with a bit of LZW-spice..
A comparison between JPEG2000 and JPG .
PNG versus TIFF
Why you should be using LZW compression on your TIFF images.