Digital BW, The Print

On 3/27/02 mwesley250@... wrote:

>Finally the "number of tones" present in a print does not depend upon the
>dynamic range or the range or the min and max. A print is an analog image
>and by definition has continuous tones that flow from one to another
>without any step change or gaps. Just as the sun sets in a smooth motion
>and not in increments, so the shades of gray flow in a continuous tone print.
>
>A silver print or negative is continuous tone by the nature of the
>chemical processes that produced it and an inkjet print is continuous
>tone by virtue of the dither pattern, variable droplet size, etc. that
>are used to produce it from a stepped digital file. By the definition of
>continuous tone there are no steps and any tone value between the limits
>of min and max can be created. Even though our eyes and instruments
>cannot distinguish between two tones, if they are too close together in
>value, does not change the fact that an infinite number of tones are
>available to the print maker in either silver or ink to create their image.

Both of these statements are true and not true. In a sort of general
hand-wavy practical way they are true, but they are inaccurate when you
get close to them.

1. No analog systems are continuous at the quantum level. Not even the
sun crossing the sky. Quantum noise is a limiting factor in many micro-
electronic systems.

2. A silver print or negative is not continuous at the granular level in
terms of its representation of the scene.

3. An inkjet print is certainly not continuous since each channel is
(currently) only capable of representing 256 shades of gray.

All of these things appear continuous if you squint hard enough but we
are not squinting in this discussion.

It is *absolutely not true* that an inky printmaker has an infinite
number of tones available. All bw output processes currently only output
8 bits or 256 tones. A quadtone system is *theoretically* capable of
representing many more tones... 256 to the power 4 in fact, which is a
hell of a lot, but no drivers that I am aware of address this ability.




-- 
John Brownlow

http://www.pinkheadedbug.com