Some years ago, I bought a special slide/ negative scanner to digitise a large number of photo
Using it, I did about half the job & saved them to the hard drive on our then XP PC.
Most less complex pictures came out OK, but several with rocks having a wide range of both colour & texture variations came out as "best guess" flat brown.
As it happened, the XP crashed, & in trying to get it back, I lost the pictures.
Luckily, I kept the original photos, so if I will be able to do it again.
This time, I will probably use an old fashioned slide duplicator & a digital camera to get the better image fidelity.
Many of the slides are about 50 years old, the dyes are still true colours, in fact, the only imperfections are some dust on them ( & those of the device looking through the viewfinder) 
The digitised ones were lost in a couple of months.
Down the "memory hole", as George Orwell put it.
If you're going to scan them again, it might make sense to do bracketed triple exposures, two stops each, that way you will be able to extract much more of the film dynamic range.
Its a bit like shooting "raw" images with a better digital camera.
By the way, have you ever tried the two programs which go under the name "testdisk" - They are available on Linux but I think they also are available on other platforms.
"TestDisk checks the partition and boot sectors of your disks.
It is very useful in forensics, recovering lost partitions.
It works with :
* DOS/Windows FAT12, FAT16 and FAT32
* NTFS ( Windows NT/2K/XP )
* Linux Ext2 and Ext3
* BeFS ( BeOS )
* BSD disklabel ( FreeBSD/OpenBSD/NetBSD )
* CramFS (Compressed File System)
* HFS and HFS+, Hierarchical File System
* JFS, IBM's Journaled File System
* Linux Raid
* Linux Swap (versions 1 and 2)
* LVM and LVM2, Linux Logical Volume Manager
* Netware NSS
* ReiserFS 3.5 and 3.6
* Sun Solaris i386 disklabel
* UFS and UFS2 (Sun/BSD/...)
* XFS, SGI's Journaled File System
PhotoRec is file data recovery software designed to recover
lost pictures from digital camera memory or even Hard Disks.
It has been extended to search also for non audio/video headers.
It searches for following files and is able to undelete them:
* Sun/NeXT audio data (.au)
* RIFF audio/video (.avi/.wav)
* BMP bitmap (.bmp)
* bzip2 compressed data (.bz2)
* Source code written in C (.c)
* Canon Raw picture (.crw)
* Canon catalog (.ctg)
* FAT subdirectory
* Microsoft Office Document (.doc)
* Nikon dsc (.dsc)
* HTML page (.html)
* JPEG picture (.jpg)
* MOV video (.mov)
* MP3 audio (MPEG ADTS, layer III, v1) (.mp3)
* Moving Picture Experts Group video (.mpg)
* Minolta Raw picture (.mrw)
* Olympus Raw Format picture (.orf)
* Portable Document Format (.pdf)
* Perl script (.pl)
* Portable Network Graphics (.png)
* Raw Fujifilm picture (.raf)
* Contax picture (.raw)
* Rollei picture (.rdc)
* Rich Text Format (.rtf)
* Shell script (.sh)
* Tar archive (.tar )
* Tag Image File Format (.tiff)
* Microsoft ASF (.wma)
* Sigma/Foveon X3 raw picture (.x3f)
* zip archive (.zip)"
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There is also ddrescue and a new one I just saw recently, this is from the debian package..
"Magic Rescue scans a block device for file types it knows how to recover
and calls an external program to extract them. It looks at "magic bytes"
(file patterns) in file contents, so it can be used both as an undelete
utility and for recovering a corrupted drive or partition. As long as
the file data is there, it will find it.
Magic Rescue uses files called 'recipes'. These files have strings and
commands to identify and extract data from devices or forensics images.
So, you can write your own recipes. Currently, there are the following
recipes: avi, canon-cr2, elf, flac, gpl, gzip, jpeg-exif, jpeg-jfif,
mbox, mbox-mozilla-inbox, mbox-mozilla-sent, mp3-id3v1, mp3-id3v2,
msoffice, nikon-raw, perl, png, ppm, sqlite and zip.
This package provides magicrescue, dupemap and magicsort commands.
magicrescue is a carver and is useful in forensics investigations."