CONCLUSION: In this test, the results are very dramatic in
showing that the 8 bit image suffers from far more posterization
and subsequent loss of detail than the 14 bit image. Because
this is such an extreme example though, the differences
seen from adjusting most images will not reflect the differences
seen here. However, for the sake of preserving as much data
as possible and enhancing image quality if heavy adjustments
are made, it is recommended that all scans be made in 14 bit
mode as default.
Many people downplay the significance of bit depth because
they don't realize just how much images are adjusted behind
the scenes. Remember that every image, even ones that will
never be touched by Photoshop, have heavy
gamma adjustments made (~2.2 for PCs) to compensate for your
monitor's non-linear response. For many scanners such as the
LS4000, this operation is performed on 8 bit data if you scan
in 8 bit mode, resulting in significant loss of data. By scanning
in 14 bit mode, you can ensure the gamma adjustments and color
management are performed on 14 bit data to minimize posterization.
If you want to save disk space or need to use tools that work
only in 8 bit mode, you can convert the files after you import
it and still preserve most of the data.