Digital BW, The Print

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 - the latter being highly correlated to the size of the pixel.  All
else being equal (including noise), greater bit depth increases dynamic
range.  This is a big "sales point" for the digital backs that are true 16
bit.  Anyway the point of the matter is there is more to a digital camera
than the number of pixels as we all know.


> From: Jeff Medkeff <medkeff@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Sat, 02 Jul 2005 12:38:40 -0800
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Artifacts with Digital images
> 
> 
> 
> Steve Kale wrote:
> 
> 
>> And better yet, more bit depth....unless you don't like dynamic range... ;-)
> 
> Wandering a bit off topic here, but it is kind of a myth that bit depth
> correlates to dynamic range. Dynamic range is physically related to the
> range of possible photosite well potentials, often called "well depth."
> This range can be sampled in as few or many bits as you want at a
> constant dynamic range.
> 
> This is why even an 8 bit ADC on an old MF digital back with gigantic
> 24mu pixels buys you so much more dynamic range than any miniature
> format (35mm size or smaller) digital camera on the market today, even
> if you read out the latter at 12 bits. The latter cameras typically have
> photosites on the order of 6 to 12 mu, and that provides a firm limit to
> the potentials available in each pixel.
> 
> What I'm getting at is that if you want more dynamic range, you should
> obsess about getting a bigger sensor with bigger photosites, rather than
> one that has an ADC that reads out more bits. I'm sure Nikon or Canon is
> going to come up with a 16 bit RAW file in the next couple generations,
> and photographers are going to freak out over it as though it is the
> Second Coming of dynamic range. But it won't actually make any
> difference to dynamic range unless there are also significant
> differences to the sensor engineering compared to current sensors.
> 
> Couple examples: I use a couple of scientific cameras that read out 16
> bits, but they have more than a stop less dynamic range than Canon's 1Ds
> II which reads out at only 12. Similarly, comparing a jpeg to a raw on
> the latter camera convinces me that there isn't a great deal of
> difference in dynamic range between the two, if any; but there is a
> useful difference in how well that range is sampled. I keep hearing
> photographers say that raw has more dynamic range than an in-camera
> jpeg, but I have a very hard time measuring this difference with my cameras.
> 
> One of the most frustrating things about digital is the fixed bit depth
> and dynamic range of the sensors. Whereas you can switch to a high
> contrast film to sample subtle tonal differences in the real world over
> a larger range of densities, digital is not so flexible. I think this is
> the source of a lot of the 'growing pains' that former film
> photographers experience when they pick up digital for the first time.
> 
> --
> Jeff Medkeff
> Eagle River, Alaska