Andy,
So, are you speaking of reciprocity failure where the actual photon
count needs to be considered? That would be at the fringe -- long
exposures where exposure = intensity × time no longer is true? It
seems to me that that would apply whether the medium was film or CCD.
But, I have no idea where this discussion would go, wrt A to D
conversion,etc.. I've read the Wikipedia article on this subject, but
it seems to apply to film only. Having said that, I don't pretend to
understand it (I'm a mechanical engineer who only needed to understand
a few things about optics, and it wasn't covered in the physics course
I took on optics at the University of Minnesota in the 50s!).
Roger
On 31 Mar 2008, at 9:39 PM, ADavidhazy wrote:
Roger,
Insightful as usual!! The truth is that I don't know the details of
my question. It is just that it struck me that electronic devices
somewhere along their "response" chain behaved like or somewhat like
film at the "toe" and "shoulder" of a film characteristic curve. And
maybe even in the midportions possibly. Is "reciprocity" or the
"reciprocity law" (actually I don't think it is a "law") followed by
digital devices since we've been shown it is not by "analog" ones
like film?
My questioning was probably actually pretty basic in scope and
understanding.
But anyone who cares to enlighten me ... by all means!! ;)
andy
Roger Eichhorn wrote:
Interesting question. Linear with respect to what? Intensity of
a single color? Or over what wavelength span? By what
measure? Output vs. input, in what units? Before or after A to
D conversion? Do you place the blame on the A side, the D side or
in between? Or am I missing the point entirely? The CCD sensors
favor Green over Red and Blue. Does this enter the picture (pun
intended)?
Roger
On 31 Mar 2008, at 4:24 PM, ADavidhazy wrote:
Robert,
Given that, why would we care a whole lot about the devices we
use being
linear?
Because I don't believe it and I think students should also
question such "absolutes" so I just wanted to be more confident
myself that I was not totally out in left field so to speak!
;)
andy
