Digital BW, The Print

On 3/28/02 12:04 PM, "Martin Wesley" <mwesley250@...> wrote:

> 
> ----- Original Message -----
> From: "Kevin Gulstene" <kevin@...>
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Sent: Wednesday, March 27, 2002 11:27 PM
> Subject: Re: [Digital BW] Dynamic Range Definitions and Print Tones
> 
> 
>> While the heavy weights take a well deserved breather I thought I'd throw
> in
>> my two cents.
>> 
>> <Geek mode on>
>> Dynamic range has a very specific meaning to people involved in signal
>> processing and designers of optical, audio and many other types of
>> equipment.  That definition is just as Austin has stated.  Dynamic Range
>> (DR) = 10log10 (smallest signal/largest signal).  Some of the confusion
>> comes from the definition of the numerator.  The "smallest signal" is not
>> the least dense or the least grey, it is the difference in density (or
>> greyness or whatever you are measuring) between one sample and another
> which
>> is the smallest possible amount greyer (or more dense or whatever you are
>> measuring).
>> 
>> If you accept the definition above, then Dynamic Range does describe the
>> number of intermediate values.  The number of intermediate values is the
>> range of values divided by the "smallest signal".
> 
> Kevin,
> 
> Thank you for the nice concise explaination. My concern with a print is that
> the "smallest possible amount grayer" will go to zero if the print or medium
> is continuous in tone which renders the expression meaningless for this
> application.

I think I am with you on this.  While I agree the "smallest possible amount
greyer" will get much smaller as the sensing technology improves, there will
always be some level at which there is a smallest possible amount (ranging
from the practical limits of our eyes to the other extreme of quantum
whatevers). More importantly we should keep in mind the purpose of the
textbook definition which is to characterise a system and not an attribute.

The text book definition of Dynamic Range is appropriate for measuring a
system.  We would have a similar problem discussing the dynamic range of a
negative.  On the other hand it is quite easy to see how the term applies to
a scanner.  In the context of a scanner (a "system" for measuring the
density of a negative) Austin's Diagram makes perfect sense.  There is a
minimum density of the negative (film base + fog) and a maximum density that
can be read by the sensor, and there is a "smallest increment of grey" that
can be measured by the "system".  This smallest increment is determined by
the system (# of bits in the ADC, the 'noise' introduced when amplifying the
signal from the sensors, etc).

In my mind, it is much easier to apply the text book definition (which I
think we agree can differ from the common use definition) to a system for
measuring an attribute of a print, than to the attribute of the print.

Ouch, I have to go find the Tylenol now.
>> 
>> <Geek mode off>
>> 
>> Having said that, it seems to me that a perfectly meaningful and
> unambiguous
>> (in any ordinary sense of those words) conversation can be had between two
>> printers using "dynamic range" and "density range" interchangeably to
>> describe the range of tones produced by an ink/paper/workflow combination.
> 
> Absolutely and this has been a common practice for quite some time.
> 
> Martin
> 
> 
> 
> 
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