Julian writes ...
> At 02:31 11/01/01, shAf wrote:
> > What you say is true, but you haven't taken into
> account the CCD's
> >response to exposure ... that is, it can't be changed.
> This means if
> >you overexpose, then you either need a very high value to represent
> >the thin area of
At 02:31 11/01/01, shAf wrote:
> What you say is true, but you haven't taken into account the CCD's
>response to exposure ... that is, it can't be changed. This means if
>you overexpose, then you either need a very high value to represent
>the thin area of the film, or you lose the detail
Hi Erik.
Erik Kaffehr wrote:
> ...Practical measurements on existing scanners seem to indicate that the
> real
> dynamic range (including CCD, elektronics, external light internal
> refkections seem in the order of 2.5, that is 8-9 aperture stops.
Acer claim a 3.2 D range for the Scanwit 27
Julian writes ...
> Can someone help me here with some basic facts regarding this
> dynamic/density range business?
>
> I am having a fundamental problem comprehending why the
> number of bits is even vaguely related to any
> supposed density range. ...
>
> For example, I could have a density ra
No I did mean 10^12 being the approximate result of my postulated 40 bits
i.e. 2^40 = 1.0995x10^12 ~= 10^12
I should have said...
The difference of course is the resolution...
In the former case, there are only 2^4 = 16 levels between darkest and
lightest density.
In the latter case, there ar
: "Julian Robinson" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, January 10, 2001 8:41 AM
Subject: Re: So it's the bits? (Was: filmscanners: Sprintscan 120 now
on B+H web site ...)
> Can someone help me here with some basic facts regarding this
> dyna
Can someone help me here with some basic facts regarding this
dynamic/density range business?
I am having a fundamental problem comprehending why the number of bits is
even vaguely related to any supposed density range. I understand the maths
quoted here and in many other posts, but fail to u
Hi!
A 14 bit number means a range 2 raised to the power of fourteen, that is
16384.
Density units are log 10 so we get log (16384) -> 4.21
A simpler way:
1 bit means essentially one one aperture stop which is 0.3 Density units (log
2).
14 * 0.3 -> 4.2
Or you could also say that the range is
So what you are saying is that the dynamic range is the number of bits
in the Analogue Digital Converter, and has very little to do with the dynamic
range of the CCD? Wouldn't it be nice with a signal to noice ration instead,
like -50 dB?
Regards
Erik
On Tuesday 09 January 2001 11:02, you w
> In summary, dynamic range is just another way of saying how
> many bits the A/D converter uses:
>
> 10 bits = 3.0
> 12 bits = 3.6
> 14 bits = 4.2
Would you please explain this more? What is the source of the information,
or the algorithm, you used to come up with these numbers?
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