Computer Graphics with Photoshop - scanned images soft

Author

scanned images soft - why ?

frankg

2004-10-02, 12:14 pm

Why are scanned images invariably soft (out-of-focus)? It doesnt matter if
the original is film (neg or transparency) or print.Can you explain it ?

I have a good film scanner (Polaroid 120) and Silverfast Ai software (which
has a focus on/off).
My flatbed is somewhat older (Microtek Scanmaker III with Scanwizard) but
still decent.

When I open the images in Photoshop I'm always disappointed in how 'soft'
they are and they Always need sharpening applied.

Apparently 'it's a fact of life' but why ?

Tom Thomas

2004-10-02, 12:14 pm

"frankg" <whosoever@wherever.com> wrote:

>Why are scanned images invariably soft (out-of-focus)? It doesnt matter if
>the original is film (neg or transparency) or print.Can you explain it ?

-- snip --

This is more related to the scanner groups than Photoshop but here's a
stab at it.

Essentially any analog to digital conversion loses fidelity because
the digital copy is produced from samples rather than a continuous
signal. In the case of a scanner, it's samples at approximately 1,000
per inch are not as sharp as the continuous tones produced by a good
camera lens [1]. This is analagous to digitally sampled music (CD)
compared to analog recording (audio tape or vinyl). The analog
version contains many subtle overtones and inflections which are lost
in the "stair step" effect of digital sampling. We accept audio CD as
a medium because of its compactness, portability and durability -- not
because it produces better sound.

You might enjoy looking at Wayne Fulton's web site, www.scantips.com .
He provides a lot of information on why scanners behave as they do,
and how to compensate.

[1] Information paraphrased from the aforementioned www.scantips.com .

-------------------------------
Tom

Unsolicited advertisements cheerfully ignored.

Stephan

2004-10-02, 12:14 pm

"frankg" <whosoever@wherever.com> wrote in message
news:h6Y6d.20537$MD5.1040394@news20.bellglobal.com...
> Why are scanned images invariably soft (out-of-focus)? It doesnt matter if
> the original is film (neg or transparency) or print.Can you explain it ?
>
> I have a good film scanner (Polaroid 120) and Silverfast Ai software
(which
> has a focus on/off).
> My flatbed is somewhat older (Microtek Scanmaker III with Scanwizard) but
> still decent.
>
> When I open the images in Photoshop I'm always disappointed in how 'soft'
> they are and they Always need sharpening applied.
>
> Apparently 'it's a fact of life' but why ?
>

Do you check sharpness with your picture open a 100% of its size?

Stephan

frankg

2004-10-02, 12:14 pm

yes

--
xx
"Stephan" <NoMoreSpam@Thank.you> wrote in message
news:pp07d.414$o27.151@twister.socal.rr.com...
>
> "frankg" <whosoever@wherever.com> wrote in message
> news:h6Y6d.20537$MD5.1040394@news20.bellglobal.com...
if[color=darkred]
> (which
but[color=darkred]
'soft'[color=darkred]
>
> Do you check sharpness with your picture open a 100% of its size?
>
> Stephan
>
>

jjs

2004-10-02, 12:14 pm

"Stephan" <NoMoreSpam@Thank.you> wrote in message
news:pp07d.414$o27.151@twister.socal.rr.com...
> Do you check sharpness with your picture open a 100% of its size?

Well, of course. And they just suck. The scanners that we modestly incomed
people can afford just suck. They ALL need a USM treatment because the
'tween shit is just terrible.

USE FILM.

Hecate

2004-10-02, 12:14 pm

On Thu, 30 Sep 2004 14:18:59 -0400, "frankg" <whosoever@wherever.com>
wrote:

>Why are scanned images invariably soft (out-of-focus)? It doesnt matter if
>the original is film (neg or transparency) or print.Can you explain it ?
>
Funny, I don't have that problem with my Minolta 5400...

--

Hecate - The Real One
Hecate@newsguy.com
veni, vidi, reliqui

Stephan

2004-10-02, 12:14 pm

"Hecate" <hecate@newsguy.com> wrote in message
news:vedpl0h1ocbcmea1f7237rhme0gtro0pjt@4ax.com...
> On Thu, 30 Sep 2004 14:18:59 -0400, "frankg" <whosoever@wherever.com>
> wrote:
>
if[color=darkred]
> Funny, I don't have that problem with my Minolta 5400...
>
Same here, I have an older slow and loud scanner but the images are razor
sharp.

Stephan

jjs

2004-10-02, 12:14 pm

"Stephan" <NoMoreSpam@Thank.you> wrote in message
news:XO47d.459$o27.384@twister.socal.rr.com...

> Same here, I have an older slow and loud scanner but the images are razor
> sharp.

It is possible that your scanning program is applying USM, and/or your
critical requisites are weak.

Scraphead

2004-10-02, 12:14 pm

I have a canon 5000f that works really well. What kind of scanner are you
talking about?

"frankg" <whosoever@wherever.com> wrote in message
news:h6Y6d.20537$MD5.1040394@news20.bellglobal.com...
> Why are scanned images invariably soft (out-of-focus)? It doesnt matter if
> the original is film (neg or transparency) or print.Can you explain it ?
>
> I have a good film scanner (Polaroid 120) and Silverfast Ai software
(which
> has a focus on/off).
> My flatbed is somewhat older (Microtek Scanmaker III with Scanwizard) but
> still decent.
>
> When I open the images in Photoshop I'm always disappointed in how 'soft'
> they are and they Always need sharpening applied.
>
> Apparently 'it's a fact of life' but why ?
>
>

Tacit

2004-10-02, 12:14 pm

>I have a good film scanner (Polaroid 120) ...

No, you do not have a good scanner; that's a big part of your problem.

Many people go to CompUSA or Best Buy and buy a scanner, and they believe they
have a "good" scanner. There is, almost by definition, no such thing as a
"good" consumer-grade scanner; decent scanners start at about $17,000 and go up
to about $320,000. I've used $320,000 scanners, and the image you get is very
crisp.

Back to your problem.

Consumer-grade film scanners suck. Not to put too fine a point on it, it's a
fact of life.

If you want a crisp scan from most consumer-grade scanners, I suggest you read
about and become comfortable with Filter->Sharpen->Unsharp Mask. Unsharp
masking (USM) is a technique for sharpening a soft image.

Some scanners do unsharp masking during the scan; check to see if your scanner
has this option. Scanners that do it will produce crisper scans than scanners
that don't. If your scanner doesn't, you'll need to unsharp mask your image in
Photoshop after it's scanned.

Unsharp masking is part art, part science. There is no set way to use it which
works for all images.

Generally speaking, however:

The Unsharp Mask filter works by exaggerating areas of high contrast--ie,
edges. This gives the appearance of sharper edges, and increases the apparent
overall sharpness of the image. While it can't make a blurred or out-of-focus
image sharp (nothing can do this), it can dramatically increase the perception
of sharpness. And unsharp masking is a requirement to get good-looking images
in print.

The Amount slider dictates how much edges are increased in contrast. If the
value in this slider is too high, the image will appear to have "halos" around
the edges.

The Radius slider determines how wide the area of enhanced contrast is around
edges. In general, the amount you put in the Radius field depends on the
resolution of the image; the higher the resolution in pixels per inch, the
wider the Radius.

A good place to start is (image resolution/200). If the image is screen
resolution--100 pixels per inch or less--try a Radius of 1. Increasin ghte
Radius will also create undesireable halos around edges.

If you are sharpening an image which will be printed on a printing press, and
your image is the recommended resolution (twice the frequency of the halftone
you will be using to reproduce the image on press), use a Radius of (halftone
screen/100). So, for example, if your image is being printed on press with a
150-line-per-inch halftone, use a Radius value of 1.5.

The Threshold command determines how far apart two neighboring pixels must be
in tonal value in order to be sharpened. I usually start with a Threshold of 3.
Lower Threshold values exaggerate noise along with edges; higher values don't
sharpen noise, but also produce more muted sharpening overall.

Note that if your image is intended for print, you should set the Amount value
so that the image looks slightly over-sharpened on your screen! This is because
the process of halftoning the image for print decreases the apparent sharpness
of the image (which is why all images should have USM applied if they are going
to be used for print).

>My flatbed is somewhat older (Microtek Scanmaker III with Scanwizard) but
>still decent.

That scanner wasn't particularly good even when it was brand-new. Sorry...

--
Art, literature, shareware, polyamory, kink, and more:
http://www.xeromag.com/franklin.html

Mike Russell

2004-10-02, 12:14 pm

jjs wrote:
> "Stephan" <NoMoreSpam@Thank.you> wrote in message
> news:pp07d.414$o27.151@twister.socal.rr.com...
>
> Well, of course. And they just suck. The scanners that we modestly
> incomed people can afford just suck. They ALL need a USM treatment
> because the 'tween shit is just terrible.

To paraphrase young Dr. Frankenstein,

USM, USM,
There's no escaping USM!

But, unlike the fate of Gene Wilder's character, there's nothing wrong with
Unsharp Mask (USM). It's a practical and mathematically valid way to make
resampled images look better. Even our own eyes use a biological variation
of USM to enhance edges.

Conventional printing and enlargement had similar techniques for sharpening
that used optics and chemistry. For example a condenser based enlarger
would print a very harsh, grainy image. A diffuser placed in the enlarger
would produce a softer, but still optically sharp image. Different methods
of development could enhance or reduce the contrast and apparent sharpness
of the image.

The name USM came from film based photography, using a blurred negative
(unsharp mask) sandwiched with the original to create sharpness. Photoshop,
and other programs, have "digitized" the methods used by conventional
photography.

> USE FILM.

There ain't nothin like a chrome, nothin in the world. But unless you are
using conventional development all the way to the final print, and few
people are these days, pretty much every pixel you capture on film will be
USM'ed at almost every stage in its digital life cycle, exactly as if it
were a digital image.

When negs and chromes scanned and digitally printed yes, Virginia, they are
will be resampled and sharpened at some point in that process. Drum
scanners, still the best scanner technology, have operator controlled USM
built into the electronics that sharpens the image as it is scanned, and the
Printer RIP does similar resampling and sharpening of image color values as
it figures out where the final dots of color should go.

But you need not look far at all to find USM. Our eyes, in a way, defined
not only the CRT's we use to view images, but the underlying algorithms that
we use to process those images for our own convenience. Our own visual
apparatus uses USM-style edge enhancement to sharpen the retinal image. So,
you see, resistance is futile, there is no escaping USM.
--

Mike Russell
www.curvemeister.com
www.geigy.2y.net

Tacit

2004-10-02, 7:14 pm

>Our own visual
>apparatus uses USM-style edge enhancement to sharpen the retinal image. So,
>you see, resistance is futile, there is no escaping USM.

Well.... If you really want to get technical (oh, boy! Let's get technical,
Tacit!), the edge enhancement in the eye doesn't work by the same technique as
unsharp masking. The effect is the same--localized contrast enhancement around
areas of dissimilar brightness--but it's not really doing USM, it's using a
different technique called "lateral inhibition." Each receptor in the eye tends
to suppress the firing of all the receptors around it when it fires.

Which gets me to wondering... It'd be relatively easy to write a Photoshop
plug-in that sharpened an image using lateral inhibition; I wonder how the
results would look when compared to unsharp masking.

--
Art, literature, shareware, polyamory, kink, and more:
http://www.xeromag.com/franklin.html

frankg

2004-10-03, 12:14 pm

jjs

2004-10-04, 11:14 pm

"Tacit" <tacitr@aol.com> wrote in message
news:20041002121519.22420.00000100@mb-m06.aol.com...
> [...]
> Which gets me to wondering... It'd be relatively easy to write a Photoshop
> plug-in that sharpened an image using lateral inhibition; I wonder how the
> results would look when compared to unsharp masking.

The eye constantly moves involuntarily (vibrates), and we tend to scan an
image as well, so lateral inhibition largely concerns small areas of the big
picture. It's done in the retina, but the brain further manages the large
picture in sections. If we saw it all at once in a single, small frame my
bet is the results would be horrible. Worth a beer bet, I think.