Re: Flatbed scanners vs Pro Photo CDs
Re: Flatbed scanners vs Pro Photo CDs
- Subject: Re: Flatbed scanners vs Pro Photo CDs
- From: Jan Steinman <email@hidden>
- Date: Tue, 5 Dec 2000 09:12:43 -0800
email@hidden (Bruce Fraser):
Bit depth has no direct relationship to dynamic range. dMax is an
analog limitation of the sensor, the point at which th esystem noise
overwhelms the signal...
Andrew Rodney <email@hidden>:
Dynamic range and bit depth have absolutely no correspondence. You can have
a 10 bit scanner with a dynamic range of 3.8 and a 12 bit scanner with a
range of 3.3...
C'mon, guys -- stop the knee-jerk response and use your noggins! :-)
Go back and re-read what I wrote. I did not write, "dynamic range and
bit depth are the same thing," I wrote, "Bits-per-pixel and Dmax
should roughly correspond." (copied directly from my posting)
Yea, you can put a 500 horsepower race car engine on a Volkswagen
drivetrain, also. But I'd suggest that should a car manufacturer do
it, it's strictly for marketing, rather than performance. If they
came up with some cheap engines, it might even make marketing sense,
since there are so many people who buy "on spec" rather than "on
performance." But it doesn't mean you can deliver a significant
portion of 500 horsepower to the pavement!
So good sensors are expensive, and good ADCs are cheap. Load a
scanner up with lots of bits you can't deliver meaningful data
through, and then hand it off to the marketing guys.
You can digitize all the worthless bits you want -- they're still
worthless. I stand by my statement. In a well-designed system,
dynamic range and quantization level WILL roughly correspond. (Before
pouncing on your keyboard, please note WELL-DESIGNED, and ROUGHLY! :-)
most CCD scanners, whatever their dynamic range, return a fair
number of bits as noise...
Well, now -- if you actually read what I wrote, isn't that what I
meant? If that wasn't clear, I apologize for not writing more clearly.
Also be aware there is no
universally accepted way of measuring dynamic range...
I guess we can sort of agree on that, except I don't believe the most
optimistic and pessimistic way of measuring this would be off by more
than a couple tenths -- ESPECIALLY since they tend to be inflated in
the same direction by marketing folks -- but I'm willing to be
educated here.
--
: Jan Steinman <
mailto:email@hidden>
: Bytesmiths <
http://www.bytesmiths.com>