Digital BW, The Print

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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