| Author |
Message |
Kennedy McEwen
Guest
|
 Posted:
Sat Nov 12, 2005 7:49 am Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
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In article <AAncf.10052$OR3.1877@tornado.fastwebnet.it>, Lorenzo J.
Lucchini <ljlbox@tiscali.it> writes
| Quote: | Kennedy McEwen wrote:
In article <g3e3n154je1ahk8ak14hjlb0lh9i0cm2ji@4ax.com>, Hans-Georg
Michna <hans-georgNoEmailPlease@michna.com> writes
Kennedy,
[snip]
Yes, it is possible - it is a technique I have used myself in imaging
systems, albeit with a deliberate and systematic misalignment between
successive frames.
[snip]
I don't know of any software that permits the automatic alignment of
frames within fractional pixel pitches for interleaving or the decision
on which frames are aligned well enough with any others in the set to be
integrated with each other.
ALE can do all that, as well as perform more geometrical transformations
than just translation in order to get images aligned.
I don't believe it can do the second requirement - which frames should |
be integrated and which should be interleaved.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying) |
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Kennedy McEwen
Guest
|
| Posted:
Sat Nov 12, 2005 7:49 am Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
In article <ewncf.10039$OR3.5274@tornado.fastwebnet.it>, Lorenzo J.
Lucchini <ljlbox@tiscali.it> writes
| Quote: | Hans-Georg Michna wrote:
Kennedy,
just a remark on the sidelines.
Actually, the fact that two successive scans are misaligned
could be used by clever software not only to yield less noise,
but even to yield a higher resolution.
I'm not sure the two can be obtained *together*, though. I think there's a
bit of Heisenberg involved ;-)
|
That depends on the ultimate output format. Simply realigning images on
a higher resolution matrix also provides many of the benefits of
multiscanning when viewed at full resolution from the appropriate
distance. It is quite amazing what the eye can achieve.
| Quote: | If multiple scans were perfectly aligned, increasing resolution
would not be possible at all.
Yes, two perfectly aligned scans won't do it. But it's dubious to me whether
you can actually achieve higher resolution even with misaligned scans
|
That isn't in any doubt, and I have built enough systems that have
proved it in side by side comparison to be convinced. The question is
whether the resolution is limited by the native sampling resolution (in
which case misalignment can offer a resolution gain if treated
appropriately) or by the system MTF (in which case it can't). Most
flatbeds fall into the latter category because they are already
utilising a form of misaligned resolution enhancement through the
HyperCCD approach. But many dedicated film desktop scanners fall into
the former category, which may make it worth the effort.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying) |
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Kennedy McEwen
Guest
|
| Posted:
Sat Nov 12, 2005 7:58 am Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
In article <1131734504.955732.237820@g43g2000cwa.googlegroups.com>,
Roger S. <rsmith02@gmail.com> writes
| Quote: | Here's the text from the VS user-guide:
"There are several ways of getting multiple image samples. The first of
these is single-pass multi-scanning. Some scanners are capable of
reading each pixel position multiple times before advancing the scan
head to a new position. The film scanners that can do single-pass
multi-scanning are the Minolta QuickScan 35, Scan Dual, Scan Dual III,
Scan Multi, Scan Multi Pro, Scan Speed, Scan Elite, Scan Elite II and
Nikon LS-2000/LS-4000/LS-8000. The second technique is multi-pass
multi-scanning, which most scanners are capable of (however, some can't
accurately reposition each scan pass, so this sometimes doesn't work
well)."
I really don't think this is adequate documentation as it doesn't tell
someone new to scanning what to look for to know if it isn't working
well.
|
Come off it Roger, it states quit clearly that some scanners aren't up
to the job. It's a user manual, not a treatise on the relative merits
of image processing techniques. It isn't a requirement of the software
vendor to explain something as trivial as the consequence of inaccurate
misalignment - there is some assumption of user competence.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying) |
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Don
Guest
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| Posted:
Sat Nov 12, 2005 8:36 pm Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
On 11 Nov 2005 10:41:44 -0800, "Roger S." <rsmith02@gmail.com> wrote:
| Quote: | I really don't think this is adequate documentation as it doesn't tell
someone new to scanning what to look for to know if it isn't working
well.
....
How about the limitations to its IT8 profiling, specifically issues
Vuescan has with non-Vuescan created profiles?
|
While it is to be expected that manufacturers don't voluntarily
advertise problems with their products (just obfuscate enough to stay
within the law) Vuescan is, indeed, in a category of its own, in this
respect. This goes far beyond the usual "caveat emptor".
The infamous Vuescan stripes with Minolta 5400 come to mind as a prime
example. There was absolutely no mention of this major Vuescan bug in
the documentation and the author persisted that Vuescan "worked" with
the 5400 for two years running in spite of numerous user complaints
screaming for their money back.
Continuing to maintain "Vuescan works with 5400" in spite of ample
proof to the contrary and failing to come clean about the bug in the
documentation was not only immoral but plain illegal. As was the
author's refusal to refund the money.
So, all the issues you raise are definitely "in character" and do not
come as a surprise.
| Quote: | I'm thinking about putting together a real world guide to image quality
with Vuescan compiling some of what I've learned over the last year and
a half.
|
That's commendable and it will surely help others but isn't that the
responsibility of the manufacturer? I mean, user-to-user support is
fine and reputable companies even offer web pages for users to
exchange tips, but when you pay for something there are minimal
requirements the manufacturer has to meet. The issues you raise (as
well as many others) squarely fall within this remit.
BTW, if you do write such a guide and dare to expose any Vuescan
"problems" expect vitriolic hate mail from the author (and he doesn't
shy from obscenities either). Judging by history, he'll probably also
tell you that you've been "blacklisted". It's not quite clear what
that means but it's some sort of delusional "excommunication"!?
Don. |
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Roger S.
Guest
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| Posted:
Sun Nov 13, 2005 12:08 am Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
Well perhaps so- it's not a requirement that the software vendor
provide this information, but this program is documented less well than
others I've used. If there were books on VS the way there were books
on Photoshop that would take the burden off of Ed, but with that said,
Adobe's documentation for how to use Photoshop is a million times
better than the cryptic guide that came with Vuescan.
That this program support so many features but not all work equally
well with every scanner made me wish, when I was a new Vuescan user,
that under the *supported scanners* description there were honest
caveats that X feature is not recommended with this scanner, instead of
leaving it to the user to figure out. You figure Ed knows all of this
from testing each scanner- why not document it for the benefit of the
users? |
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Lorenzo J. Lucchini
Guest
|
| Posted:
Sun Nov 13, 2005 8:25 am Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
Kennedy McEwen wrote:
| Quote: | In article <ewncf.10039$OR3.5274@tornado.fastwebnet.it>, Lorenzo J.
Lucchini <ljlbox@tiscali.it> writes
[snip]
Yes, two perfectly aligned scans won't do it. But it's dubious to me
whether you can actually achieve higher resolution even with misaligned
scans
That isn't in any doubt, and I have built enough systems that have
proved it in side by side comparison to be convinced.
|
Kennedy, you snipped the part where I said *in what context* I don't think
resolution can be gained...
You say you have *built* systems where it works. Built. What kind of systems
were they? As I said in the part you snipped, normal consumer-grade scanner
produce significant amounts of misalignment *that varies from scanline to
scanline*. That won't happen in, say, a digital scanner, or a
high-precision scanner system you may have built.
How is any software going to correct for misalignment that, for all intents
and purpuses, can vary at every pixel? If it does *not* vary, then it's a
whole different thing. But in scanners people normally have in this
newsgroup, it does vary.
| Quote: | The question is
whether the resolution is limited by the native sampling resolution (in
which case misalignment can offer a resolution gain if treated
appropriately) or by the system MTF (in which case it can't). Most
flatbeds fall into the latter category because they are already
utilising a form of misaligned resolution enhancement through the
HyperCCD approach. But many dedicated film desktop scanners fall into
the former category, which may make it worth the effort.
|
I think that's a big "may". I mean, it's certainly something that would be
interesting to try, I just think the probabilities of success are very low,
for the reasons I mentioned above. But then, perhaps some "dedicated film
desktop scanners" have really really good mechanics, who I am to know. (Or
rather, what money do I have to know ;-).
by LjL
ljlbox@tiscali.it |
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Lorenzo J. Lucchini
Guest
|
| Posted:
Sun Nov 13, 2005 8:25 am Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
Kennedy McEwen wrote:
| Quote: | In article <AAncf.10052$OR3.1877@tornado.fastwebnet.it>, Lorenzo J.
Lucchini <ljlbox@tiscali.it> writes
Kennedy McEwen wrote:
In article <g3e3n154je1ahk8ak14hjlb0lh9i0cm2ji@4ax.com>, Hans-Georg
Michna <hans-georgNoEmailPlease@michna.com> writes
Kennedy,
[snip]
know of any software that permits the automatic alignment of
frames within fractional pixel pitches for interleaving or the decision
on which frames are aligned well enough with any others in the set to be
integrated with each other.
ALE can do all that, as well as perform more geometrical transformations
than just translation in order to get images aligned.
I don't believe it can do the second requirement - which frames should
be integrated and which should be interleaved.
|
I think it can. It outputs a "match percentage" number for every image, and
you can set a threshold on that to decide whether to keep or discard an
image.
I'm going by memory though, I'd have to check the manual.
by LjL
ljlbox@tiscali.it |
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Kennedy McEwen
Guest
|
| Posted:
Sun Nov 13, 2005 6:01 pm Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
In article <1131818897.270412.187540@o13g2000cwo.googlegroups.com>,
Roger S. <rsmith02@gmail.com> writes
| Quote: | Well perhaps so- it's not a requirement that the software vendor
provide this information, but this program is documented less well than
others I've used. If there were books on VS the way there were books
on Photoshop that would take the burden off of Ed, but with that said,
Adobe's documentation for how to use Photoshop is a million times
better than the cryptic guide that came with Vuescan.
That this program support so many features but not all work equally
well with every scanner made me wish, when I was a new Vuescan user,
that under the *supported scanners* description there were honest
caveats that X feature is not recommended with this scanner, instead of
leaving it to the user to figure out. You figure Ed knows all of this
from testing each scanner- why not document it for the benefit of the
users?
As a general rule, making the product itself is only a small part of the |
activity and documenting it can be far more expensive. The more
detailed that documentation is, the more expensive it becomes.
I am quite sure that if a majority of Vuescan users asked Ed to document
the software as thoroughly as Photoshop he would oblige - and price the
product accordingly!
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying) |
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Kennedy McEwen
Guest
|
| Posted:
Sun Nov 13, 2005 6:29 pm Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
In article <OAydf.471$P16.13@tornado.fastwebnet.it>, Lorenzo J. Lucchini
<ljlbox@tiscali.it> writes
| Quote: | Kennedy McEwen wrote:
In article <ewncf.10039$OR3.5274@tornado.fastwebnet.it>, Lorenzo J.
Lucchini <ljlbox@tiscali.it> writes
[snip]
Yes, two perfectly aligned scans won't do it. But it's dubious to me
whether you can actually achieve higher resolution even with misaligned
scans
That isn't in any doubt, and I have built enough systems that have
proved it in side by side comparison to be convinced.
Kennedy, you snipped the part where I said *in what context* I don't think
resolution can be gained...
Having looked at your previous posting again Lorenzo, there doesn't seem |
to be any additional context that I snipped. The text I quoted was your
in-line reply to Hans-Georg's statement - and I specifically kept the
part about correct alignment no providing any gain to keep your comment
in context. You did make additional comments over and above that, but
see below.
| Quote: | You say you have *built* systems where it works. Built. What kind of systems
were they?
|
Mainly military scanned imaging sensor systems, but one or two
industrial imaging sensor systems I designed used a systematic
misalignment between frames to achieve increased resolution, which was
measured in test rooms.
| Quote: | As I said in the part you snipped, normal consumer-grade scanner
produce significant amounts of misalignment *that varies from scanline to
scanline*.
|
Yes, I snipped because it was "in addition to" your original comment as
covered by your "come to think of it" statement, not a contextual
qualifier.
| Quote: | That won't happen in, say, a digital scanner, or a
high-precision scanner system you may have built.
Don't bet on it - military kit is reliable, but the precision is often |
no better than commercial, particularly when the kit is operating at the
extreme of its mechanical design envelope, such as on a fast jet pulling
maximum g or a tank manoeuvring over rough terrain.
| Quote: | How is any software going to correct for misalignment that, for all intents
and purpuses, can vary at every pixel? If it does *not* vary, then it's a
whole different thing. But in scanners people normally have in this
newsgroup, it does vary.
The question is whether it varies significantly enough to prevent |
consistent alignment to half a pixel accuracy or so. That isn't so
demanding as your overarching statement, and many scanners are indeed
capable of this. Even for those where frame to frame alignment might be
out by more than a pixel, making dumb multipass multiscanning (as in
Vuescan) worthless, the variation across the field on each frame can
easily be less than half a pixel.
| Quote: | The question is
whether the resolution is limited by the native sampling resolution (in
which case misalignment can offer a resolution gain if treated
appropriately) or by the system MTF (in which case it can't). Most
flatbeds fall into the latter category because they are already
utilising a form of misaligned resolution enhancement through the
HyperCCD approach. But many dedicated film desktop scanners fall into
the former category, which may make it worth the effort.
I think that's a big "may". I mean, it's certainly something that would be
interesting to try, I just think the probabilities of success are very low,
for the reasons I mentioned above. But then, perhaps some "dedicated film
desktop scanners" have really really good mechanics, who I am to know. (Or
rather, what money do I have to know ;-).
Let's just say that the alignment of consecutive scans on my Nikon |
LS-4000 is certainly better than half a 4000ppi pixel across the frame,
although the frame to frame alignment itself certainly is a lot worse.
There ay well be long term variations, say if one scan was performed
several hours after the other, but consecutive scanning is pretty good.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying) |
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Hans-Georg Michna
Guest
|
| Posted:
Sun Nov 13, 2005 8:08 pm Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
On Wed, 09 Nov 2005 18:17:06 +0100, Don wrote:
| Quote: | in
case of LS-50 and other 4000 dpi scanners, in practical terms, they
already extract the maximum resolution from average film.
|
Don,
that doesn't coincide with my observations at all, based mostly
on my Nikon LS-4000 ED. I had already discussed that with
Kennedy, and if I reproduce the results correctly, all common
4000 ppi scanners are unsharp, to say it simply. If they had the
required optics to make the best possible 4000 ppi picture file
from a photo or slide, then you would be right, but the required
optics would be extremely expensive and totally out of the
question.
Therefore all scanners, particularly the amateur ones like mine,
make compromises, yielding 4000 ppi pictures that are simply not
as sharp as the original film.
I guess that, to reproduce most of what's in a 35 mm slide,
you'd need to buy a scanner with a resolution of 8000 to 12000
ppi. You could then reduce the resolution of the resulting files
by means of a good filter, like Lanczos, without losing very
much. But a normal 4000 ppi scanner will not yield the same
quality by far.
Very unfortunate, but this is how it is. Of course the happy guy
who has just shelled out thousands to buy his wonderful 4000 ppi
scanner won't like to hear that at all. Sorry, folks.
Hans-Georg
--
No mail, please. |
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Hans-Georg Michna
Guest
|
| Posted:
Sun Nov 13, 2005 8:08 pm Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
On Sat, 12 Nov 2005 01:49:36 +0000, Kennedy McEwen wrote:
| Quote: | Most
flatbeds fall into the latter category because they are already
utilising a form of misaligned resolution enhancement through the
HyperCCD approach
|
Kennedy,
ah, I didn't know that. Must read up on it.
These flatbed scanners are really cheap these days. Just bought
a little Canon LiDE 60 for something around ¤60, which is
nothing compared to what scanners used to cost a couple of years
ago.
Hans-Georg
--
No mail, please. |
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Hans-Georg Michna
Guest
|
| Posted:
Sun Nov 13, 2005 8:08 pm Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
On Wed, 09 Nov 2005 15:15:38 +0100, Lorenzo J. Lucchini wrote:
| Quote: | it's dubious to me whether
you can actually achieve higher resolution even with misaligned scans: come
to think of it, scans are not just *misaligned* in your everyday scanner,
but they're misaligned in ways that vary *in* the image.
The top may have some amount of average misalignment, the bottom may have
some other amount, *and each row or column might have a different and
random amount of misalignment* due to errors in the motor steps
(vertically) and loose movement of the CCD array (horizontally).
How would software find out about all this?
No, I think multi-scanning, in practice, will be much more useful for noise
reduction, with scanners.
|
Lorenzo,
we're leading a highly speculative discussion now, but for the
sake of entertainment, I'd say that it would be interesting to
find out how scanners actually misalign successive scans of the
same photo. Perhaps it's not as bad as you think.
But even if, say, a slide slowly moves during a scan, software
could still transform the resulting slightly distorted images.
It could, for example, work not just with a linear model on the
entire picture, but could align pieces. Autostitch gives a vague
indication what's possible.
It would be interesting to be able to obtain a higher resolution
from a relatively cheap scanner, even if it takes long, just for
the one very important photo.
Hans-Georg
p.s. Looked at ALE and liked what I saw, but I simply don't have
the time to learn and understand all those parameters. I would
need an automatic program that's easy to use.
--
No mail, please. |
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Hans-Georg Michna
Guest
|
| Posted:
Sun Nov 13, 2005 8:08 pm Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
On Thu, 10 Nov 2005 18:35:06 +0100, Don wrote:
| Quote: | I understood Hans-Georg's subtext to mean that even though I was
right, I went too far with my reply to Fred. Specifically, it was
H-G's phrase "that reply of yours was not actually needed". You know,
as in "that was way over the top" or "easy now, no need for that".
But you're absolutely right, that phrase could be interpreted in two
different ways: 1. My reply is redundant, or 2. My reply goes too far.
|
Don,
sorry for being ambiguous, but I did indeed mean that your
message in question was correct, and Fred's unwarranted attack
on it only confirmed that he had nothing substantive to reply.
I usually take such attacks as a confirmation of the attacked
message.
Hans-Georg
--
No mail, please. |
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Lorenzo J. Lucchini
Guest
|
| Posted:
Sun Nov 13, 2005 9:23 pm Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
Kennedy McEwen wrote:
| Quote: | In article <OAydf.471$P16.13@tornado.fastwebnet.it>, Lorenzo J. Lucchini
ljlbox@tiscali.it> writes
Kennedy McEwen wrote:
In article <ewncf.10039$OR3.5274@tornado.fastwebnet.it>, Lorenzo J.
Lucchini <ljlbox@tiscali.it> writes
[snip]
Yes, two perfectly aligned scans won't do it. But it's dubious to me
whether you can actually achieve higher resolution even with misaligned
scans
That isn't in any doubt, and I have built enough systems that have
proved it in side by side comparison to be convinced.
Kennedy, you snipped the part where I said *in what context* I don't think
resolution can be gained...
Having looked at your previous posting again Lorenzo, there doesn't seem
to be any additional context that I snipped. The text I quoted was your
in-line reply to Hans-Georg's statement - and I specifically kept the
part about correct alignment no providing any gain to keep your comment
in context. You did make additional comments over and above that, but
see below.
|
Hm well then, I don't remember exactly what I wrote; I could search back, of
course, but suffice to say that my intention was not to make a general
statement that "higher resolution is not attainable by means of merging
multiple misaligned images", but just that "higher resolution is probably
not attainable in consumer scanners because of lack of mechanics
precision".
I do realize that the theory behind it all is valid, and that the
mathematics would indicate a resolution gain is possible.
| Quote: | You say you have *built* systems where it works. Built. What kind of
systems were they?
Mainly military scanned imaging sensor systems, but one or two
industrial imaging sensor systems I designed used a systematic
misalignment between frames to achieve increased resolution, which was
measured in test rooms.
As I said in the part you snipped, normal consumer-grade scanner
produce significant amounts of misalignment *that varies from scanline to
scanline*.
Yes, I snipped because it was "in addition to" your original comment as
covered by your "come to think of it" statement, not a contextual
qualifier.
That won't happen in, say, a digital scanner, or a
high-precision scanner system you may have built.
Don't bet on it - military kit is reliable, but the precision is often
no better than commercial, particularly when the kit is operating at the
extreme of its mechanical design envelope, such as on a fast jet pulling
maximum g or a tank manoeuvring over rough terrain.
How is any software going to correct for misalignment that, for all
intents and purpuses, can vary at every pixel? If it does *not* vary, then
it's a whole different thing. But in scanners people normally have in this
newsgroup, it does vary.
The question is whether it varies significantly enough to prevent
consistent alignment to half a pixel accuracy or so. That isn't so
demanding as your overarching statement, and many scanners are indeed
capable of this. Even for those where frame to frame alignment might be
out by more than a pixel, making dumb multipass multiscanning (as in
Vuescan) worthless, the variation across the field on each frame can
easily be less than half a pixel.
|
But if, say, the first scan line is "correct", and the last scan line is off
by half a pixel (or even more!), we can still do a geometrical
transformation to correct for this, can't we (ALE does this)?.
What I'm dubious about is what happens when *each* scan line is off by a
significant amount. At the end of the scan, the first scan line and the
last scan line could even both be in perfect alignment, if the previous
errors averaged out. But in this case, I can't think of a way ALE or any
other program could reasonably reconstruct alignment...
| Quote: | [snip]
I think that's a big "may". I mean, it's certainly something that would be
interesting to try, I just think the probabilities of success are very
low, for the reasons I mentioned above. But then, perhaps some "dedicated
film desktop scanners" have really really good mechanics, who I am to
know. (Or rather, what money do I have to know ;-).
Let's just say that the alignment of consecutive scans on my Nikon
LS-4000 is certainly better than half a 4000ppi pixel across the frame,
although the frame to frame alignment itself certainly is a lot worse.
There ay well be long term variations, say if one scan was performed
several hours after the other, but consecutive scanning is pretty good.
|
But even if the alignment is better than half a pixel across the frame, what
is the average misalignment between a pixel (or scan line) and the next?
Isn't this the most important factor?
Again, *across-frame misalignment* can be corrected for anyway, I think, as
a program like ALE has enough data to deduce the amount of misalignment. I
cannot really think of a way to guess the amount of scanline-to-scanline
misalignment, as a program could only deduce it using the data from *one*
scanline!
by LjL
ljlbox@tiscali.it |
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Lorenzo J. Lucchini
Guest
|
| Posted:
Sun Nov 13, 2005 9:42 pm Post subject:
Re: What is better Nikon Super Coolscan 4000 or Coolscan V E |
|
|
Hans-Georg Michna wrote:
| Quote: |
On Wed, 09 Nov 2005 15:15:38 +0100, Lorenzo J. Lucchini wrote:
it's dubious to me whether
you can actually achieve higher resolution even with misaligned scans:
come to think of it, scans are not just *misaligned* in your everyday
scanner, but they're misaligned in ways that vary *in* the image.
The top may have some amount of average misalignment, the bottom may have
some other amount, *and each row or column might have a different and
random amount of misalignment* due to errors in the motor steps
(vertically) and loose movement of the CCD array (horizontally).
How would software find out about all this?
No, I think multi-scanning, in practice, will be much more useful for
noise reduction, with scanners.
Lorenzo,
we're leading a highly speculative discussion now, but for the
sake of entertainment, I'd say that it would be interesting to
find out how scanners actually misalign successive scans of the
same photo. Perhaps it's not as bad as you think.
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Perhaps.
| Quote: | But even if, say, a slide slowly moves during a scan, software
could still transform the resulting slightly distorted images.
It could, for example, work not just with a linear model on the
entire picture, but could align pieces. Autostitch gives a vague
indication what's possible.
|
Yes, *if a slide slowly moves during a scan* (or rather if the stepping
motors slowly drifts).
ALE can do it, and not just by "working with pieces", but by actually
automatically performing transformations (shrinking, enlargement, rotation
even) on each image. Sorry for sounding like an advert for ALE, I'm not
involved in it in any way, I just think it's a cool program.
But I'm more dubious on what could happen if the misalignment doesn't just
change slowly, but has significant errors at *each* scan line -- errors
which, in the end, could even average out to zero, giving the impression of
*no* error at all! And still, it would be worse than "a slide slowing
moving during the scan".
| Quote: | It would be interesting to be able to obtain a higher resolution
from a relatively cheap scanner, even if it takes long, just for
the one very important photo.
|
Yeah, running ALE does take *very* long though for big images, at least
here.
| Quote: | Hans-Georg
p.s. Looked at ALE and liked what I saw, but I simply don't have
the time to learn and understand all those parameters. I would
need an automatic program that's easy to use.
|
I think you guys here in CPS are simply scared by the command line :-P
ALE does have a lot of parameters, as any complex and powerful program, but
it also has reasonable defaults for the times you don't want to use all
those parameters.
Just specify:
ALE image_1 image_2 ... image_n output_image
and you'll be able to merge frames in a multi-pass multi-scan way (but
*with* the realignment).
This way, the output image will not have more resolution than the input
images, just (hopefully) less noise. If you want to try what we're talking
about in this thread, you can do
ALE --scale=x image_1 image_2 ... image_n output_image
where x is the scale factor (2 for example).
In both cases, you'll be using defaults (specifically, you'll default to
option "--q0") that try to make the process fast (sort of), but sacrifice
quality.
Add options "--qn", "--q1" or "--q2" (sorted by quality, from lowest to
highest) to change that. I think that, for experimenting with resolution
improving, one should use either "--q1" or "--q2", while "--qn" could be
adequate for normal multi-pass multi-scanning (the "n" in "--qn" stands for
"noise").
Also, by default, ALE only tries applying "Euclidean" (translation,
rotation) transformations to re-align images. You can specify
--projective
to get all the transformations ALE is capable of, or
--translation
if you are in a hurry.
There are a ton more parameters that can be used, but hey, if you trust the
program's authors as far as the program code is concerned, you could trust
them on their choice of default parameters as well! At least if you don't
have long hours to waste.
by LjL
ljlbox@tiscali.it |
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