RE: [APML] Picture Window Pro vs. PhotoShop

["Koebel, Alen" <Alen.Koebel@christiedigital.com>]

Thor Olson wrote:

> Jerry is right though, the display itself
> is really only an 8-bit device, and if the same 8-bit frame
> is displayed from a 16-bit original, there is no physical
> distinction.

The operative word here is "same." It could be that in converting from 
the 16-bit frame, the software "dithers" the data in the least significant
bit or bits according to what is in the byte not being displayed, instead
of simply truncating it. This is a common technique that trades off some
spatial noise in the image for better perceived tonal gradations near 
black. 

> The issue here is most likely dynamic range of the print versus
> the monitor.  Many prints have a tough time making a 100:1 contrast
> range from black to white.  CRTs are considered a 100:1 device, and
> projected slides in a dark room can approach 1000:1.  Obviously with
> a smaller contrast range, fewer levels (bits) are needed to smoothly
> span the range.

Dynamic range AND the transfer curve (value in, light out). The transfer
curves are different for all the display devices you mentioned above. As
an extreme example, a display device with a linear curve needs many more
bits than one with a power-law curve (the CRT monitor being a typical
example of the latter). BTW, that figure of 100:1 for a CRT monitor 
would only be true in a lighted room. It will be much higher (>1000:1) 
in a dark room. 

--  APML Archives at <http://astro.umsystem.edu/apml/>  ---
             Unsubscribe at <majordomo@seds.org>