Digital BW, The Print

Anthony,

> No, they are not.  Photons of certain energies produce a reaction more
> readily than others.

Look at the B&W photoresponse curve.  Along the ENTIRE spectrum of the film,
they produce nearly similar reaction.  This is what's important, as the B&W
film is NOT color sensitive because of this response.

> > Look at the film response curve for B&W film.  It's reasonably
> > flat, up to the point of fall-off.
>
> It looks irregularly curved to me.  It can be dramatically changed by
> filters, too.

Well, it's not irregular enough to be significant.  Yes, it can be
dramatically changed by a lense cap as well.  They both have the same
relevance to this discussion.

> > Now, does the RGB data not have this "intensity"
> > information?
>
> RGB data, like B&W data, is an integration of the area under one or more
> curves.  The curves themselves are lost in the process.

And, that's not relevant.  If the intensity information is maintained, then
you've got all you need.

> > Does it matter that different combinations of RGB
> > produce the same intensity?
>
> What matters is the spectral distribution in the original scene.

Not at all.  What matters is the INTENSITY of the original scene.

> I'll try again, although I'm not optimistic that anyone who hasn't already
> understood will understand from this:
>
> Set up two omnidirectional microphones in the middle of an orchestra, and
> record some music.  At the same time, set up two other microphones, in two
> completely different positions, and record the music with those, too.

Yeah, they will be very different in amplitude, and it also depends on how
they are aimed, but no matter what, since the distances between the sound
and the microphones are different, which changes the amplitude, the results
will be different.

> Now take the recording from one set of microphones, and transform
> it into a
> recording of the music as heard from the other two microphones.

I don't believe it can be done, since there are complex frequencies
involved...which is an entirely different case from converting RGB color
data into B&W data.  Audio is NOT point sourced, images are.  Audio data is
also not static, it requires surrounding data to evaluate a single point.
Image data does not.

> You may be
> surprised to discover that it cannot be done.

Not surprised at all, being that I designed a lot of digital imaging
equipment, and consulted to a lot of top sound engineers (both live and
studio) who used our equipment.

> In fact, even if you use two mics for the first recording, and
> only one mic
> for the second (like RGB to B&W), it still can't be done.

And once again, your analogy is entirely irrelevant.  Image data is static,
audio data is not.  Image data is point sourced, audio data is not.

Austin