----- Original Message -----
From: "David A. Mann"
Subject: Re: Is the New LX Going to Be a Digital
Camera
> William Robb writes:
>
> > I do have a question about film to digital
> > comparisons. What is the comparative image
depth
> > of film to digital capture? I know the
digital
> > guys talk about 36 bit depth, but how does
that
> > tranlate to the capture depth of a long
scale
> > film such as Portra?
> > Is 12 bits per colour the equivalent of 12
stops
> > of tonal range?
>
> Not necessarily. Each bit might not
represent a doubling of the actual light
> intensity, even though it will represent a
doubling of signal out of the CCD's
> analogue electronics.
>
> 12 bits will represent a range of 4096 levels
(per colour). The important part
> is how the range is scaled. Those 4096 levels
might represent a 1-stop tonal
> range with _heaps_ of tonal detail within that
range. Which is great if your
> lighting is flat. But when the sun comes out
it'd respond like lith film :)
>
> In reality there's a bit of a tradeoff
between tonal range and tonal detail, within
> the limits of the CCD (dynamic range,
linearity and noise).
That is sort of where I was going with that
question. In digital, we hear lots about image
resolution, like as if that is the most
important criteria, but not so much about image
depth. This is also a concept I am a bit fuzzy
on. I know it roughly translates as tonal range,
and that more is better (possibly even more
important than absolute pixel count).
What I would like to know is what sort of
dynamic range in stops (a concept I do
understand) does a CCD chip have? Is it variable
based on software or is it hardware limited?
Is it closer to a short range slide film such as
Velvia? Or closer to a long range print film
such as Portra NC?
Or is the question to general to give a specific
answer to?
Thanks
William Robb
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