Digital BW, The Print

David Whistance wrote:
> 
> 
> I'm not sure where this comes from. 16 bits of data gives 2 to the power of
> 16 shades of grey, ie 65,536 of them. Should be plenty to divide by 17
> stops, particularly as the relationship between a stop and a set of shades
> of grey is arbitrary - you can map them how you like with either the scanner
> software or Photoshop. What does surprise me is that Steve gets this from
> an Epson V700, however I've seen some of his images and he does undoubtedly
> capture a very large SBR with detail at both ends so I'm sure he's right.

No one is questioning that David gets a tremendous SBR; it's the
specific number that sounds too good to be true.

Dynamic range of a sample is limited to log-base-2(#levels).
This is a theoretical limit; it assumes a perfect sampling
chain.  Real-world performance is not going to be as good
in general, there's a noise floor in the electronic chain,
flare in the optics and limitations in the A/D converter itself.

So, in theory, the most that could be represented in a scan is
16 stops; practically speaking, it's probably more like 14 stops.

Cheers,
Dana