Re: Scanner woes

If i use a 3 bit A/D i will have 8 buckets for data. If i use an 8 bit A/D i will have 256 buckets. i will get very different results for a continuous tone image if i use the 3 bit A/D and stretch it to a 8 bit range (using levels in PS for example). i will have 8 different tones with gaps between in the 256 different tone levels! (This is what happens during leveling when you see gaps open up in the histogram of the image where before there were values in a narrow band only). Using the 8 bit A/D i can more or less get a continuous gradation from "white" to "black". If the image only has 3 bits worth of range, then Don is correct and it will not make any difference.

A practical example of this is a "line art" scan of a typed *** of paper - a 1 bit A/D implementation. Everything is "black" or "white". OCR software does a little bit better if the scan is done in "grey scale" - 8 bit, 16 bit whatever, so that it can see some of the smudges (and half tone patterns) that connect the dots on the page and interpolate the pattern more or less correctly to make a letter.

BTW, anyone heard from Kennedy lately ?

regards,

Alex Wilde wrote:
In message <pf0p72ta4pm6v6egi5bp212j0i2udo14j4@xxxxxxx>, Don <phoney.email@xxxxxxxxx> writes

No. That's a common misconception. Scanner software is actually
composed of two *unrelated* components: the actual scanning (i.e.
getting data from the scanner) and the editing tools.

So, in theory, it doesn't matter if you let the scanner software do
everything in one big gulp (i.e. scan and edit together) or scan "raw"
and do you edits later.

So what you are saying is that no setting in the editing tools of Nikon Scan has any effect on the data pulled from the hardware? It only effects the output, and I can do that better in PS?

However, in practice scanner software editing tools are usually a poor
substitute (i.e. a very limited quick-and-dirty subset) of standalone
external editors like Photoshop. They exist only for marketing reasons
and people for whom that's good enough and they can't justify the cost
of a dedicated editor or wish to spend the extra time.

I understand this, and would rather edit in PS. I won't edit all the images, just the ones that I want to print, but I thought I might as well scan them all as best I could, then they can always be edited at a later date.


The 16-bit editing mode in Photoshop *6* is actually only 15-bit!
However, since CoolScan V is 14-bit that shouldn't be a problem,
right? Well, it is because gamma and calibration of this raw 14-bit
data is done using the full 16-bits in NikonScan. So, in theory you
may lose some data. But wait, there's more! ;o) Since you're scanning
negatives, they have a (vastly) reduced dynamic range, you will never
push at the limits of 14-bit let alone 16.

So, the bottom line in case of negatives is, you can skip that last
paragraph! ;o)


I usually have to convert the images I've edited to 8-bit anyway, but I leave the original in 14-bit so I can maybe take more advantage of them if I later get more up to date software. If I'm gonna scan all these boxes of negatives, I only wanna do it once.
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