Digital BW, The Print

On 3/28/02 1:22 PM, "Martin Wesley" <mwesley250@...> wrote:

>> 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.
> 
> Hmmm. That is the same as saying there are no analog systems since the very
> concept of analog means continuous.

Not at all. An analog system or device is one that represents data variation
by a measurable physical quality. You are arguing that that is continuous,
not me.
> 
>> Not even the
>> sun crossing the sky.
> 
> The rotation of the earth occurs in small steps and not in a continuous
> motion? An apple falls to the ground in distinct intervals? I know back to
> my rubber example but reality moves form state to state hitting all the
> positions in between without breaks or step changes.

I am just being pernickety. At the sub-atomic level it all falls apart. An
electron does not trundle from A to B like a billiard ball. For this reason,
neither does the sun. It is almost infinitely unlikely, but perfectly
possible, that one day the sun will hop from one point of the sky to the
other. That's the nature of quantum unpredictablity.

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

> Not as a representation of the scene perhaps but... [SNIP]

We are talking about it as a representation. That's the whole point of the
discussion.

>> All of these things appear continuous if you squint hard enough but we
>> are not squinting in this discussion.
> 
> I don't have to squint at all to look at the real world and see that is full
> of continuous tones and motions. Remember the idea of usable or meaningful
> values. Taking things down to the level of quantum mechanics may not be
> helpful in establishing values to assess the relative merits of one printing
> medium over another.

Certainly agreed.
>> 
>> 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.
> 
> Well you can control where those 256 bits fall within a tonal range and if
> you can do that, any tone is available to you even if you can only get a
> finite number of them into a particular print. Think of it this way. Within
> the range, what density can't I reproduce in an inkjet print?

You can map each of those 256 brightness values to any output value you like
but that doesn't make it a continuous tone image. There are still 256
brightness levels in the output image with discrete steps in reflectance
between them.

-- 
John Brownlow

http://www.pinkheadedbug.com