Digital BW, The Print

It depends. For a given number of pixels the
additional surface area of a full frame (24X36mm)
sensor would provide a larger pixel and thus better
signal to noise (all other things being equal). But
the camera makers are in a race for megapixels based
on the marketing value of winning that race. Thus
Canon, who have a full frame sensor have opted for
16.7 megapixels i.e. pixel sites where Nikon, with an
APC size sensor have limited to 12.4mpx. MF makers
such as Hasselblad and Mamiya have even larger sensors
but are stuffing 22.5mpx onto them. Dalsa is building
the sensors for Mamiya and Dalsa have peltier cooled
sensors in use for the motion picture industry. So
they have the technology to make a difference but
given price premium that would be required it is very
unlikely (IMHO) that techology will trickle down to
still cameras.

woody

--- Richard <richard@...-bulldog.com> wrote:


---------------------------------
On the basis of what you have claimed below, can we
assume a single bit chip
24x36mm would be the ultimate?

Richard

> -----Original Message-----
> From: DigitalBlackandWhiteThePrint@yahoogroups.com
>
[mailto:DigitalBlackandWhiteThePrint@yahoogroups.com]
On Behalf Of Jeff
> Medkeff
> Sent: Saturday, July 02, 2005 10:32 PM
> To: DigitalBlackandWhiteThePrint@yahoogroups.com
> Subject: Re: [Digital BW] Artifacts with Digital
images
> 
> 
> 
> Steve Kale wrote:
> 
> 
> > Yes I guess this is a bit off this topic but there
is an interesting
> > discussion here from which I conclude we want
greater bit depth and
> lower
> > noise
> 
> Amen to that.
> 
> 
> > All
> > else being equal (including noise), greater bit
depth increases dynamic
> > range.
> 
> No, that's just not correct. Sorry, it is not my
intention to be merely
> contentious; I think this is an important user issue
with respect to
> digital cameras. All greater bit depth gives you is
better (finer)
> sampling of the dynamic range the sensor can sense.
> 
> If you take a Kodak test strip - one with "black" at
one end, "white" at
> the other, and a bunch of grays in between - you
could slice that up
> into 8 equal pieces with an x-acto knife, or you
could slice it up into
> 12 equal pieces. Although the size of the pieces
gets smaller, your top
> and bottom ends remain the same no matter which you
do.
> 
> This is analogous to what is happening in a digital
camera - well
> potential is being amplified and sent through an
analog-to-digital
> converter. You could have that converter output in
eight bits, ten,
> twelve, or fifty, but changing ADCs would *never*
change the potential
> in the well. The only thing you change with bit
depth is the tonal
> "distance" between steps. Remember these sensors are
linear, unlike film!
> 
> It is more correct to say that all other things
being equal, greater
> photosite size increases dynamic range. The rubber
meets the road for
> photographers when choosing a camera; there isn't
much relevance to this
> at exposure time when you are already committed.
Paul's 8 megapixel XT
> is a great camera. But it and its brother the 20D
both have less -
> considerably less - dynamic range than Canon's 1D
mark II. The 1D II
> does not read out more bits, nor does it have more
pixels, nor is it
> lower in intrinsic noise. What it has are larger
photosites.
> 
> OTOH when shooting a scene with a large dynamic
range, then you want as
> many bits as you can come by - I don't dispute this.
This isn't because
> it lets you record more range before blowing the
highlights or burying
> the low end in mud; it is because you want all the
flexibility you can
> get when you pull that range to the gamut of an
output device and start
> to put tree trunks in the histogram. This is a
separate issue.
> 
> All this is measurable. Don't take my word for it;
if dynamic range is
> important to you, it is a pretty easy job to compare
the dynamic range
> of different cameras to an adopted level of the
signal's statistical
> significance.
> 
> 
>  > This is a big "sales point" for the digital backs
that are true 16
> > bit.
> 
> The digital backs have greater dynamic range, but
this is not a result
> of their bit depth. Rather the reverse is true -
they *need* to sample
> with more bits due to the greater dynamic range; if
they did not, the
> flux differences between adjacent ADU's would
eventually grow large
> enough to appear posterized even in the
unmanipulated, linear image.
> Somewhere around here I've got images read out from
engineering grade
> sensors that show just this effect, using 35mu
photosites and 8 bit ADCs.
> 
> --
> Jeff Medkeff
> Eagle River, Alaska
> 


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