Re: Scanning & TWAIN

["Maris V. Lidaka, Sr." <mlidaka@xxxxxxxxxxxxx>]

Just a few thoughts.

First of all, get some more RAM - RAM is cheap these days.  I don't know how to work with the image while leaving TWAIN open but it will go much faster if you add 384 MB RAM for under $100.

Essentially, you need to set the black and white points.  The problem with opening up shadow detail lies in the midpoint - the gamma setting.  That is probably the setting to work with primarily.

(1)    AFAIK you should be able to crop using the trannie - it sounds unusual.

(2)    I don't know the way around this.

(3)    AFAIK the verbal settings merely change the scanning spi - your primary selection should be the spi (samples per inch or ppi) and you can select that using either the verbal settings or by typing in the spi you desire.  AFAIK the Printer choices are the same.  Look to the numbers, rather than to Epson's descriptions.

(4)    Try out Vuescan - I have not used it on B&W but it is designed to and does capture all possible information in the image.  You can set the black and white points, and set the gamma (though this is not intuitive - I believe that in its latest incarnation gamma is set by the "brightness" control), and you will have to do further adjustments in PS but the information will be there with which to do it.

Maris



----- Original Message ----- 
From: "Michael Healy" <mjhealy@kcnet.com>
To: <scan@leben.com>
Sent: Saturday, March 02, 2002 3:09 PM
Subject: Scanning & TWAIN


| I wonder whether I might get some thoughts and feedback on a few problems
| I'm having in the use of TWAIN.
| 
| I am scanning with an Epson 2450, TWAIN, and PS 5.5, driven by a Pentium 3
| with 12-gigs and 96 megs of RAM. I am interested primarily in making
| high-quality scans of b&w negs for digital enlargement to be used in contact
| printing. My negs are 6x9 and 4x5. I am prepared to work my images in
| PhotoShop, but I want very much to maximize the scan quality in the first
| place so as to avoid excessive handling and "fixing" as a result of
| incompetent scans. Right now I am experimenting with TWAIN's gray scale --
| scanning, evaluating histograms, then rescanning with scale adjustments. I'm
| not only trying to master the options, but I want to nail down the variables
| so I know what I'm doing when I think I need to adjust one.
| 
| That is the background. My trouble is that what I want requires more control
| than TWAIN seems willing to afford. Or rather I should say, more information
| than it will surrender. I frankly do not find TWAIN very forthcoming about
| what it's actually doing in there. EG, I can alter the scan's gray scale,
| but I cannot figure out what the gray scale actually is by "default" before
| I alter it. Does anyone know what TWAIN's "auto" gray scale values actually
| are? How about its "reset" scale? Do I need to hunker down and coax this
| information indirectly from histograms by experimenting?
| 
| Another problem seems to be inconsistencies in these outcomes. Last week I
| scanned a neg with "auto". It seems to open up shadow detail. (This was on
| negs scanned into positives, though, so my observation is backwards from
| what it is when I scan them as neg-to-neg.) Also, my use of "auto" does at
| least establish a benchmark. From there, I am systematically adjusting the
| pre-scan gray scale and rescanning. This is giving me a number of carefully
| planned outcomes, with histograms that I am able to evaluate. It is a
| wonderful exercise in how to get intuitive with histograms -- kind of like
| learning how to instinctively gauge the need of a subtle change on the
| enlarger.
| 
| Today, though, when I repeated the same scan, I actually got a different
| histogram result! It's a better one, with values more evenly distributed;
| but I didn't want a better one, I wanted the same one. I wonder why I'm
| unable to achieve the identical result. Incidentally, this is not because I
| was playing with bit depth or size. And so I keep circling around the
| meaning of "auto" and "reset" in this thing. These variables seem to elude
| precise defintion. As a photographer I am accustomed to making careful
| shifts away from an established value, AFTER establishing that value, not
| simply as arbitrary shifts in relation to some undefined "default" I can't
| measure.
| 
| Other questions about TWAIN while I'm on the subject:
| 
| (1) Is it me (or the 2450), or does TWAIN not permit cropping with the
| overhead transparency reader? I preview for a print, and I am able to crop.
| I preview for a transparency, and I can't. Probably there is some logical
| design reason for this, but it sure seems to be one of the stupidest
| shortcomings I've encountered in all my years w/computers.
| 
| (2) How come I am unable actually to handle a scanned image unless I first
| close TWAIN? The images are there on my PhotoShop workspace, but TWAIN won't
| surrender to Photoshop. This means, EG, that I can't evaluate an image's
| histogram on the fly. I have to close TWAIN, play with the image, reopen
| TWAIN, and kick in yet another preview. This is time-consuming, and seems
| ludicrous. I don't seem to recall experiencing this problem last summer
| while using TWAIN through PS 6 on a new Microtek (in Mac...) Is this a
| limitation in my own system? Even a single scan of 500k can't be accessed
| w/o closing TWAIN, so I seriously doubt it's my RAM.
| 
| (3) What is the difference between OCR, Epson Printer (Fine), and Epson
| Printer (Photo)? I understand that OCR is for line drawings and especially
| text. What I can't seem to pin down in my readings, though, is the
| implication in a scan of a continuous tone slide or neg. And what
| implication is in the Printer choices? Are these just more consumer-pleasing
| bells and whistles, or do they alter outcomes? If so, in what measurable
| ways?
| 
| (4) What about other scan drivers? I have tried SilverFast and absolutely
| despise it. If TWAIN throws us impenetrable "auto" and "reset", SF needs to
| dump two dozen slabs of mystery meat labeled "Agfa" and "Ilford Delta 100",
| whatever the hell THESE built-in gray scales even might do. To someone
| trying to actually measure and gauge, this seems like 50 steps back, not two
| steps forward.  Mike Demyan has suggested VueScan. I've reviewed their
| website, and it looks promising -- does it address some of these issues more
| transparently? Are there other pros and cons?
| 
| Thoughts and feedback appreciated.
| 
| Mike Healy
| 
| 
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