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"Digital ICE" without Digital ICE

 
 
Lorenzo J. Lucchini
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      10-26-2004
First, sorry for cross-posting, I admit I just posted to the two
groups where the topic of Digital ICE seems to come up most often.

I'm a newcomer in digital photography and scanning, so the ideas I'll
discuss below might very well be badly flawed - please bear with me.

Ok, you have a flatbed scanner with a transparency adaptor; it's got
two lamps, one below the glass and one above. Film is supposed to be
scanned with the top lamp.

But what happend if you scan film with the bottom lamp, possibly with
the lid open and in a dark room?
The scan will show an almost completely black film, since nearly no
light passed through it. However, dust particles and white-ish
scratches on the film will (or might) reflect the light from the
bottom lamp, and thus will easily be spotted in the scan! (or will be
after some histogram normalization).

The rest is just a software process of applying dust-removal filters
on the spots in the image we know dust lies.


What do you think? I *have* actually tried this stuff and it *appears*
to work and remove a number of defects from the final image - although
many dust spots remains, and I haven't been able to find out whether
the system works differently with dust that's *on the film* and dust
that's *on the scanner*.

However, after cleaning the scanner's glass as carefully as I could, I
still think I'm spotting particles that do lie on the film surface.
Then maybe it also depends which side of the film dust lies on.


I'll post sample pictures and some sketched Bash scripts using NetPBM
for the actual picture cleaning if anybody's interested.


by LjL
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Matt Ion
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      10-26-2004
Lorenzo J. Lucchini wrote:

> What do you think? I *have* actually tried this stuff and it *appears*
> to work and remove a number of defects from the final image - although
> many dust spots remains, and I haven't been able to find out whether
> the system works differently with dust that's *on the film* and dust
> that's *on the scanner*.


Interesting concept, and should somewhat work in theory, although it
will only work for "noise" that's between the film/negative and the
scanner head. Dust that's on "top" of the film (facing the upper light
head) won't be detected by the reflective scan. Also, if the noise is
severe enough to block light on a transmissive scan, the reflective scan
may give you a "cancellation" image for it, but the information in the
film itself will still be obscured by it.
 
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Gadgets
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      10-26-2004
Interesting idea, but you'd need your object to be in the exact same place
when you lifted the lid. Maybe it could work if you put glass over your
orig.

Cheers, Jason (remove ... to reply)
Video & Gaming: http://gadgetaus.com
 
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Lorenzo J. Lucchini
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      10-27-2004
Matt Ion <(E-Mail Removed)> wrote in message news:<9nhfd.23441$%k.13864@pd7tw2no>...
> Lorenzo J. Lucchini wrote:
>
> > What do you think? I *have* actually tried this stuff and it *appears*
> > to work and remove a number of defects from the final image - although
> > many dust spots remains, and I haven't been able to find out whether
> > the system works differently with dust that's *on the film* and dust
> > that's *on the scanner*.

>
> Interesting concept, and should somewhat work in theory, although it
> will only work for "noise" that's between the film/negative and the
> scanner head. Dust that's on "top" of the film (facing the upper light
> head) won't be detected by the reflective scan.


I'm not sure. It's true that there is dust that doesn't get detected,
but after a few experiments my opinion is that it's either because
they're too small, too dark to reflect enough light, or out-of-focus
(ie on the glass).

What you say is probably true if I do the "defect scan" with the lid
closed, which reduces contrast between image data and noise data, so
making the particles that lie on top of the film too dim for
detection; with the lid open, however, that doesn't seem to be the
case.

(Actually, it obviously *will* be the case for particles that lie on
top of a *dark region* of the film, but those particles won't do much
damage to the final image anyway)

> Also, if the noise is
> severe enough to block light on a transmissive scan, the reflective scan
> may give you a "cancellation" image for it, but the information in the
> film itself will still be obscured by it.


Sure, but AFAICS this applies to real Digital ICE as well - if
information is lost, it's lost, but we can try to mask the loss by
interpolation or some like technique.

On the topic of the noise-masking algorithm... what I do now is simply
- create a very blurred version of the scan
- superimpose the blurred version onto the original version, using the
"defect scan" as an alpha channel so that the blurred version is only
shown where there are defects

However, this doesn't seem to work very well, since the color of the
final image looks quite a bit different from what you'd expect in the
noise spots.

What's a better idea? I've read Digital ICE simply divides every image
pixel by the corresponding pixel in the "defect scan" (an IR scan in
ICE's case).
After trying this, though, it doesn't seem to work well at all: the
features of dust spots in my "defect scans" probably differ a lot from
ICE's IR scans.

Now I'm entertaing myself with the idea of using a median filter,
which seems to preserve pixel colors fairly well while removing most
defects; what do you think?

I'm not at home at the moment, but I'll upload some of my scans as
soon as I'm back.

by LjL
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Lorenzo J. Lucchini
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      10-28-2004
I've uploaded a picture cleaned using my method.

You can find the original slide as scanned at
http://ljl.150m.com/slide_original.jpg

The cleaned picture is at
http://ljl.150m.com/slide_clean.jpg

The "noise map" as scanned (lid open, little ambient light) is at
http://ljl.150m.com/slide_map.png

There is post-processed version of the noise map, which is the one
actually used as the alpha channel, at
http://ljl.150m.com/slide_nmap.png


All the scans were made at 1200 dpi, 24-bit color with an Epson RX500.
The "image scan" and the "noise scan" have been hand-aligned, since my
scanner doesn't pick up the same image area in film mode as in flatbed
mode.
The final images have been scaled down (Paint Shop Pro, "Pixel
Resize") to be 800 pixels wide.

As you can see, I didn't get the histogram stretching quite right for
the "normalized noise map": I made the darkest 97% of pixels black,
and the brightest 0.1% white, which seems to be definitely overkill. I
need to experiment a bit more with this.

You can see how I also applied a convolution (whatever a convolution
is) to dilate the noise spots, in order to avoid the edges of the dust
particles to show up in the final image.


by LjL
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Ken Weitzel
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      10-28-2004


Lorenzo J. Lucchini wrote:

> The cleaned picture is at
> http://ljl.150m.com/slide_clean.jpg


Hi Lorenzo...

It appeasts that slide_clean.jpg "cannot be shown because
it contains errors"

Perhaps upload it again?

Ken

 
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Lorenzo J. Lucchini
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      10-28-2004
Ken Weitzel <(E-Mail Removed)> wrote in message news:<GPXfd.42103$nl.6158@pd7tw3no>...
> Lorenzo J. Lucchini wrote:
>
> > The cleaned picture is at
> > http://ljl.150m.com/slide_clean.jpg

>
> Hi Lorenzo...
>
> It appeasts that slide_clean.jpg "cannot be shown because
> it contains errors"
>
> Perhaps upload it again?


Strange, it works here, and both slide_original.jpg and
slide_clean.jpg were converted to JPEG using PSP.
I'll convert it again using NetPBM, err, I mean, I'll do it after The
Simpsons
Also expect a slide_original.png and a slide_clean.png, but please
don't download these massively since my bandwidth is limited.

by LjL
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Lorenzo J. Lucchini
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      10-28-2004
(E-Mail Removed) (Lorenzo J. Lucchini) wrote in message news:<(E-Mail Removed). com>...
> Ken Weitzel <(E-Mail Removed)> wrote in message news:<GPXfd.42103$nl.6158@pd7tw3no>...
>
> > [snip]

>
> Strange, it works here, and both slide_original.jpg and
> slide_clean.jpg were converted to JPEG using PSP.
> I'll convert it again using NetPBM, err, I mean, I'll do it after The
> Simpsons


I've succesfully opened both files with Opera and MSIE on two
computers. I guess you simply accessed them while sitecopy was
updating the site, or while something else weird was happening on the
web server.
Anyway, I've now uploaded a slide_clean_b.jpg made with NetPBM.

> Also expect a slide_original.png and a slide_clean.png, but please
> don't download these massively since my bandwidth is limited.


I didn't upload these ones, because my web server apparently forbids
files bigger than one megabyte.

by LjL
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Don
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      10-28-2004
On 27 Oct 2004 09:16:49 -0700, (E-Mail Removed) (Lorenzo J.
Lucchini) wrote:

> What do you think? I *have* actually tried this stuff and it *appears*
> to work and remove a number of defects from the final image - although
> many dust spots remains, and I haven't been able to find out whether
> the system works differently with dust that's *on the film* and dust
> that's *on the scanner*.


I really like your lateral thinking (well done!!!). Unfortunately,
using the flatbed to scan first as transparency and then laying the
film on the scanner and scanning as reflective introduces far too many
problems to be effective.

Besides the obvious such as flaws (both scratches and dust) on top of
the film which will not be detected in the reflective scan, there are
other far more serious problems, in particular alignment.

Regarding flaws within the film itself (e.g. scratches) the alignment
between the two scans will be way off on both axis. Indeed, there are
bound to be all sorts of spatial distortions and I would expect the
two images to be of totally different sizes making it impossible to
accurately superimpose in order to identify the flaws.

Regarding surface particles (e.g. dust), once you've moved the film
you've dislodged some dust and introduced other. Therefore, surface
debris between the two scans will not correspond anymore. In other
words, you'd be "cleaning" dust which doesn't exist and, yet, leaving
dust which does.

So in both instances (internal and external flaws) the alignment,
which is the cornerstone of the method, will itself be flawed.

Nevertheless, I really must commend you again on creative thinking!

Don.
 
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Mendel Leisk
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      10-29-2004
(E-Mail Removed) (Lorenzo J. Lucchini) wrote in message news:<(E-Mail Removed). com>...
> (E-Mail Removed) (Lorenzo J. Lucchini) wrote in message news:<(E-Mail Removed). com>...
> > Ken Weitzel <(E-Mail Removed)> wrote in message news:<GPXfd.42103$nl.6158@pd7tw3no>...
> >
> > > [snip]

> >
> > Strange, it works here, and both slide_original.jpg and
> > slide_clean.jpg were converted to JPEG using PSP.
> > I'll convert it again using NetPBM, err, I mean, I'll do it after The
> > Simpsons

>
> I've succesfully opened both files with Opera and MSIE on two
> computers. I guess you simply accessed them while sitecopy was
> updating the site, or while something else weird was happening on the
> web server.
> Anyway, I've now uploaded a slide_clean_b.jpg made with NetPBM.
>
> > Also expect a slide_original.png and a slide_clean.png, but please
> > don't download these massively since my bandwidth is limited.

>
> I didn't upload these ones, because my web server apparently forbids
> files bigger than one megabyte.
>
> by LjL
> (E-Mail Removed)


Lorenzo, your first jpeg link appears to be to a maliscous site...

Any idea why this should be???
 
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