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[filmscanners] Re: Density vs Dynamic range



On Tue, 11 Jun 2002 11:46:10 -0500, Laurie Solomon wrote:
>Thank you for this very lucid and clear definition;s clarify
>things
>for me on this front with respect to the concept of "resolution."   Then,
>am
>I correct in saying that notions such as dpi, ppi, number of pixels, and
>bit
>depth are all means of measuring resolution but from different
>perspectives?

I'll jump back in for a moment.  Resolution is being used in the sense of
being able to separate something into parts.

DPI, PPI,# of pixels are all ways of measuring how a scanner can separate
an image into multiple(Ok, thousands or millions of parts) in space.

Bit depth will determine how finely a color can be described as different
"shades" of R, G, or B.  Or how many shades of R,G, or B there are to
describe the color at any individual pixel.


As far as the rest of the argument - be careful what you take from it.
There is just too much arguing and misinformation flying around as fact.
Add to that a good dose of arrogance and asocial behavior, and a real
discussion just doesn't seem to be happening.

Jon




>
>-----Original Message-----
>From: filmscanners_owner@halftone.co.uk
>[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Anthony Atkielski
>Sent: Tuesday, June 11, 2002 3:11 AM
>To: laurie@advancenet.net
>Subject: [filmscanners] Re: Density vs Dynamic range
>
>
>"Resolution" can refer both to the ability to distinguish between
>different
>intensities and the ability to distinguish between spatially separated
>details.  It can be used to refer to the distinctions between different
>hues
>or saturation levels, too.  It just means how much or how many
differences
>can be seen or rendered in some aspect of the image.
>
>----- Original Message -----
>From: "Laurie Solomon" <laurie@advancenet.net>
>To: <anthony@atkielski.com>
>Sent: Tuesday, June 11, 2002 06:34
>Subject: [filmscanners] RE: Density vs Dynamic range
>
>
>I am not going to get into this highly technical discussion where I do
not
>belong as an active participant; however, I do have a question.  When you
>say, "Resolution here is the number of discrete shades of R, G or B," are
>we
>using the same term, "resolution," or using the term in the same way as
>when
>we speak of "resolution" in terms of ppi, dpi, line pairs, or number of
>pixels?  If so, I am confused since I did not think that this really had
>anything to do with the number of discrete shades of R,G, or B but with
>the
>number of R,G, and/or B pixels that there were regardless of the shade
>they
>portrayed.  I further understood the number of discrete shades to be
>represented by "bit depth" not "resolution."
>
>If the term, "resolution," is not designated the same thing as indicated
>by
>ppi, dpi, line pairs, and numbers of pixels but  is being used
differently
>or to designate something entirely different then knowing this is the
case
>would reduce my confusion and clarify the comments for this layman.
>
>-----Original Message-----
>From: filmscanners_owner@halftone.co.uk
>[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Jonathan King
>Sent: Monday, June 10, 2002 10:45 AM
>To: laurie@advancenet.net
>Subject: [filmscanners] Re: Density vs Dynamic range
>
>
>Ok, I bitten my tongue long enough.  It hurts!
>
>
>On Mon, 10 Jun 2002 10:32:30 -0400, Austin Franklin wrote:
>>
>>
>>>However my point is that if you can reduce the noise level then you can
>>>increase the number of steps (by halving the step size) with real
>>>benefit, but without altering the range.
>>
>>Hi Peter,
>>
>>Correct, but that INCREASES the dynamic range.
>>
>
>
>
>No it doesn't.  You are confusing dynamic range and resolution.  Doubling
>the number of steps & halving the step size will keep the same dynamic
>range, but it will double the resolution.  Resolution here is the number
>of discrete shades of R, G or B.  Peter's point is that if the noise of
>the system is greater than the step size, decreasing the step size will
>just digitize noise - Not Good, unless you play with digital processing
>techniques, as alluded to.
>
>
>
>
>>>My principle argument was that a 5000:1 ratio does not specifically
>>>define
>>>that 5000 steps are requires
>>
>>Well, yes it does...that's what it means, with respect to what we are
>>talking about.  Go download a few linear CCD specs (or if you want, I
can
>>mail you some), and you'll see they talk about it in exactly the same
way
>>I
>>do.
>>
>Try this one, unless there is a better example.  It looks like a nice CCD
>for a 4000dpi, 120 film scanner?
>
>http://www.kodak.com/US/plugins/acrobat/en/digital/ccd/kli8023Long.pdf
>
>FYI Kodak defines dynamic range pretty much the way engineering schools
>I've attended in the U.S., and apparently Ireland, do:  Max. Output level
>divided by the dark noise level.
>
>>>Just a quick question - do CCDs really use a +/- voltage swing? I'd
have
>>>thought that would have introduce noise problems around 0.
>
>It looks like the Kodak chip uses only positive voltages, but the output
>has a DC offset that the buffer amplifier and A/D have to deal with.
>
>
>If you want to split technical hairs, please at least be willing to state
>and consistently use terms.  First Nyquist, and now this.  It has the
>appearance of trying to baffle the non-technical( Wow, photographers
don't
>need engineering degrees? ;), but doesn't provide any clarity.
>
>Best Regards,
>
>Jon
>
>
>
>
>
>
>
>
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