Digital BW, The Print

>> But, in short, most people are of the mind that bit depth and
>> dynamic range
>> are independent qualities, or that's how I've interpreted them.
> 
> Well, they just aren't.  You absolutely do need so many bits to represent an
> entire range of integer density values over a particular dynamic range.  It
> just works that way.  It's like saying counting and numbers are independent.

>> I'll venture
>> they may be right when considering the attributes of a file already before
>> us, but not realize it's a little different when we are discussing the
>> elements of a capture device.
> 
> I am specifically talking only about image capture devices.  I don't know
> what you mean by the attributes of a file already before us.

Put aside how the image was captured; I'm talking (for the moment) about a
file of unknown origin (which is what I mean by "a file already before us").
You can have a file with a DR of 4.0 of any bit depth, and you can have a
file of any bit depth with a DR of 1.7. In this sense BD and DR are
independent. I'm just saying that the DR of such an image certainly can be
adjusted independent of it's BD once it's in hand. You can adjust the file's
end points and spread or condense the tones at will without needing to alter
it's bit depth in order to do so.

Now, I can see if you put in the qualifier that it is essential that the
tones in the file also be contiguous integer density ratio values. (which I
take it you are saying is how digital capture devices work) then I can see
how that changes things.

Am I making sense? Am I getting you right?

>> That¹s because Leaf provides you untonede (linear) raw data.
>> Newer scanners
>> can provide high bit files that are toned.
> 
> Toning has nothing to do with it.  Toned data is NOT raw data.  Toning data
> also does NOT really spread it out, setting the setpoints spreads it out,
> whether you chose to tone it or not.  He is talking about something other
> than raw data.  You CAN get both high bit raw data, and high bit toned data
> out of newer scanners.

I think colloquially he's referring to setting endpoints as toning, but I
agree with you that any manipulation of the file makes it something other
than raw. But a lot of scanner operators would love to get toned highbit
data from their scanners. I think he was just speaking to the possibility of
that option.

>> and you can have a scanner with 12 bits and a dynamic
>> range of 3.8.
> 
> Absolutely wrong.  A dynamic range of 3.8 specifies integer ratio values
> from 1 to 6,309, which means you need a number of bits that can hold these
> numbers, and 12 bits can only hold 4,096 different values.
> 
>> Bit depth is the number of steps. Dynamic range is
>> the height
>> of the star case. You can have a staircase that¹s 20 feet high and have 40
>> steps. You can have a staircase that¹s 30 feet high and have 30 steps.
> 
> He is right, but contradicts his example above!  If you have a bit depth of
> 12, as he states above, you only have 4,096 steps.  If your dynamic range is
> 3.8, which is 10**3.8 or 6,309...you don't have enough steps to hold it.
> Pass this along to him and see what he has to say.

Austin, if you'd like to help me somehow put all of this into a coherent
question, or challenge, to put out there to those "experts" who declare that
DR is independent of BD, I'll be happy to post it. I'd love to hear their
responses. OTOH, THEY may very well appreciate the education!

Thanks again,
Todd