Digital BW, The Print

In a message dated 11/28/2003 5:47:47 PM Pacific Standard Time, 
DigitalBlackandWhiteThePrint@yahoogroups.com writes:

> You can't get infrared B&W from any
> conversion of RGB, nor can you get UV from RGB conversion.  The reason
> for this is the same as indicated above.
> 

Neither can B &W film unless it's responsivity happens to be in that band. 
One of the pluses of Tech pan is it's extended red sensitivity (besides the 
microfine grain).

You can easily photograph Infra Red with digital. In fact, solid state 
sensors are wildly sensitive to IR. This is where they have the greatest Quantum 
Efficiency. Camera designers heavily attenuate that responsivity with Cyan 
filters to try and only keep the visual light response. Stephen Johnson was lucky 
enough to get one of the rare Kodak 460 (6 MPix) cameras that has not IR filter 
or Bayer filters on it. So he can filter out the visible light in part or in 
it's entirety if he wishes.

Anthony.......it's not that we don't get it, it's just that we don't all 
agree with you from a practical standpoint.

As long as each of the RGB channels can record a full, printable dynamic lum
inance range (7-8 stops) over the entire 400-700 nm band at unity gain (which 
the Foveon X3 can), from the original scene, there is no infomation missing at 
all, and you can post process anything you prefer later. If you want the full 
dynamic range of the chip available to you, then optionally  shoot RAW in most 
cameras (which you must in the Sigma) and you can extend that luminance range 
for all the channels and move your printable window later.

The minute you use your "narrow" minded (band) filter over the lens, you 
restrict that frequency responsivity and create a unique relationship with the 
resultant densities on the film, but you are now STUCK with it? So are you going 
to expose a sheet of film with every filter in the bag and apply all those 
filter factors and bracket, too? What's so unique about that? When you do the 
full bandwith capture with ALL the colors of the original scene, you can be even 
more selective, manipulative, and selective later on from just a single RAW 
exposure, or several (on a tripod) if you wish to record an extended dynamic 
range.

For gosh sakes, all we are trying to do is get a few hundred smooth gray 
tones from paper white, to Dmax of the inks. Why make it so difficult?

Claude


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