on 8/26/02 11:35 AM, Austin Franklin at darkroom@ix.netcom.com wrote:
> Hi Roy,
>
Hi Austin,
...
> When you set the setpoints, these 2000 values are then mapped out to occupy
> the entire range. You then apply your tonal curves to the high bit,
> setpointed data.
Ok, Austin, let's go with your numbers.
Is the number 2000 now a measure, indication or whatever
of the dynamic range of the image at this stage?
Read it into PS. Convert 16-bit to 8-bit -- now 256 levels.
Is the number 256 now a measure, indication or whatever
of the dynamic range of the image at this stage?
If you answered "yes" to both Dyr questions, does the 8-bit image
have 1/8 the dynamic range of the 2000 level image?
Austin, we all know how scanners and printers work, I'm asking
the three above questions from a definitional point of view --
YOUR definitional point of view.
>
>> Going further, the printers themselves
>> don't print 256 levels.
>> Some of the best results these days are quadtone
>> inkjets. That's 4 levels of gray ink plus of course the white of the
>> paper i.e. 5 levels total. Each dot on the paper can be one of 5
>> possible gray values. So, we have images going from 16384 levels
>> to 256 levels to 5 levels -- and we're all pretty happy with the
>> results.
>
> That is not how printing works. There is a dither/halftone pattern
> involved, and the number of perceivable tones that are printed are far more
> than 5. Piezo can clearly print in the hundreds, and they claim "more than
> a thousand". You REALLY don't believe a quadtone printer only prints 5
> perceivable levels?
Yes, I know how printers work and all that. Simple question:
If I've got a densitometer that measures an area exactly the same size
as one dot on the paper, how many possible levels do you expect it to
be able to report?
--------------------------------------------
>
> Possibly to someone who doesn't understand this, because your "answer" is
> simply a wrong answer. Dynamic range IS unquestionably the number of
Actually, you've had many, many people question the claim, otherwise there
wouldn't be so many posts about it. To date, you're the sole person that
I know of to actually argue your side of the debate.
> levels. I'll reference you to something I've already posted, but appears
> you either ignored, or missed:
>
>
>
> It CLEARLY states that the number of digitization levels is the same as
> dynamic range, providing you want to digitize down to noise.
>
> "The dynamic range is often represented as a log ratio..."
> "This ratio also gives an indication of the number of digitization levels
> that might be appropriate for a given sensor...Unless there is a desire to
> resolve ... noise".
I see the words "...indication...that might be appropriate..."
and you translate that to "...is the same as...". Hmmm.
>
>> Please, think about it.
>
> Oh, I have...and I keep reaching the same conclusion ;-)
>
> Austin
>
Roy
Roy Harrington
roy@harrington.com
Black & White Photography Gallery
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