RE: [APML] Picture Window Pro vs. PhotoShop

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

Philip Perkins wrote:

> And as we know, 8 bits is all that is needed for any image to 
> be viewed by the human eye, by whatever medium.  

Sorry, but I can't agree. I have viewed test images from DLP Cinema 
projectors with very high brightness and contrast ratio, and 
capable of 15-bit linear grayscales. The difference between 8-bit 
gamma-encoded images and 10-bit gamma-encoded images is quite 
noticeable. The 8-bit images have obvious posterization near the 
black level (which is where you will most see the difference). 
For *this* medium (bright, high-contrast projected images) viewed 
by the human eye, eight bits is NOT all that is needed. 

The number of bits that are needed to display an image without 
noticeable steps anywhere in the grayscale (most noticeable near
black) depends on (a) the contrast in the image, (b) the 
brightness of the image, and (c) the encoding method of the data 
(e.g., linear, log, gamma/power-law). The higher the contrast 
(density in photographic terms) and/or brightness, the more bits 
are needed. Linear encoding needs more bits than gamma encoding, 
etc. Which all means, to get this back on topic, that the number 
of bits needed for a print may be different than the number of 
bits needed for display of the same image on a monitor. Or on a 
projector. It is true that 8 bits works well for these 
applications most of the time. But not all of the time.

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