Vuescan Multi Pass Scanning/focus (Canon FS4000US)

[John]

Whats this supposed to do? I can't see any difference even at 16x (scanning
at 4000 dpi).

When setting focus options is it better to focus at preview, scan or both?
As preview is lower resolution do you get better results focussing on the
main scan?

How does auto focus work and is this done on the whole frame or just part?
Suppose the picture is slightly out of focus to start - is it better to
manual focus?

 

[Kennedy McEwen]

Whats this supposed to do? I can't see any difference even at 16x (scanning
at 4000 dpi).

It reduces noise on the scanned image by averaging over several scans.
You are unlikely to see the difference by magnifying the image, but if
you pull the deep shadows up to a visible range using a curves or levels
adjustment, then the difference will be much clearer. If you are trying
to get the maximum information off of the film then multiscanning is
useful, since all films have more dynamic range than the signal to noise
of current CCDs. Some scanners provide single pass multiscanning, but
Vuescan offers the capability to all the scanners it supports by using a
multipass scanning option.

 

[Bruce Graham]

Whats this supposed to do? I can't see any difference even at 16x (scanning
at 4000 dpi).

Unless you are scanning dark slides or negatives with very dense
highlights you do not need to worry about this. Even then, you can save
some time by trying the "long exposure pass" option which seems to work
well with the Canon (it has an adjustable exposure, some scanners don't).

When setting focus options is it better to focus at preview, scan or both?
As preview is lower resolution do you get better results focussing on the
main scan?

The Canon has a reasonable depth of field and a focus on preview will
give a good scan. However, I use the "both" setting to make sure because
I may have previewed another frame before I get around to scanning. It
only takes a few seconds, but the option is there to cut it out and save
time if you have a big batch of scans.

How does auto focus work and is this done on the whole frame or just part?
Suppose the picture is slightly out of focus to start - is it better to
manual focus?

autofocus works well. You select the focus point in Vuescan - it is the
flashing target thingy you see on the preview screen and you can move it
to a critical part of your image if you wish.

 

[tomblue]

Some scanners provide single pass multiscanning, but
Vuescan offers the capability to all the scanners it supports by using a
multipass scanning option.

How does Vuescan ensure accurate registration between multiple scans on
"all the scanners"?

 

[Ed Hamrick]

How does Vuescan ensure accurate registration between multiple scans on
"all the scanners"?

VueScan doesn't do accurate registration between multiple scan
passes. To do this would require buffering the entire scan multiple
times, and this is too memory- and cpu-intensive.

Regards,
Ed Hamrick

 

[Bart van der Wolf]

How does Vuescan ensure accurate registration between multiple
scans on "all the scanners"?

It relies on the hardware's positioning accuracy (which is not
perfect).
There is no separate re-alignment functionality in the software :-(
If you want to do sub-pixel accurate re-alignment (hor/ver only)
yourself, you'll need software like the Reindeer Graphics' Optipix
plug-ins (http://www.reindeergraphics.com/optipix/guide/layer.shtml).

Bart

 

[Ivan]

Unless you are scanning dark slides or negatives with very dense
highlights you do not need to worry about this. Even then, you can save
some time by trying the "long exposure pass" option which seems to work
well with the Canon (it has an adjustable exposure, some scanners don't).

Would a very high key scene such as snow qualify as a dense negative? If a
person didn't have multi pass scanning capability, would it be an easier
scan if the snowy scene was photographed on positive film?
Ivan

 

[Bruce Graham]

Would a very high key scene such as snow qualify as a dense negative?

If the snow has been exposed with a simple meter won't it be underexposed
and a bit thin? Assuming it IS correctly exposed, there will be a large
average density, but no particularly dense bits and so no real problem.

On my scanner (Canon4000) most colour negs can be scanned OK, but with a
bit of noise in some highlights. eg. a shot into a hazy sun where you
still want to see some detail in the very bright surrounding cloud and
with a couple of stops + compensation to hold foreground shadow detail.
The Vuescan long exposure pass worked well for me on that. The other
times I have used it are on black and white negs with strong highlights
and some overdevelopment.

If a
person didn't have multi pass scanning capability, would it be an easier
scan if the snowy scene was photographed on positive film?
Ivan

the old guide: with slides, expose for the highlights, (which is easy in
snow) with negs, expose for the shadows. Both can give a correctly
exposed image which is easy to scan.

 

[Wilfred]

The Canon has a reasonable depth of field and a focus on preview will
give a good scan. However, I use the "both" setting to make sure because
I may have previewed another frame before I get around to scanning. It
only takes a few seconds, but the option is there to cut it out and save
time if you have a big batch of scans.

In that case you can also use "fous at scan" only, provided that the
preview comes out sharp without focusing. With my scanner (not a Canon
but a Minolta) this mostly works well and it saves time.

 

[RSD99]

"Ivan" asked:
"...
Would a very high key scene such as snow qualify as a dense negative?
...."

No.

Dense = Dark

 

[Wilfred]

"Ivan" asked:
"...
Would a very high key scene such as snow qualify as a dense negative?
..."

No.

Dense = Dark

Yes. For a negative, dense = light
For a slide, dense = dark.

 

[tomblue]

VueScan doesn't do accurate registration between multiple scan
passes. To do this would require buffering the entire scan multiple
times, and this is too memory- and cpu-intensive.

Regards,
Ed Hamrick

Thanks, ED. Your product description and site should include this
statement. Even if all the scans are buffered, there is no guarantee
that they will be, or can be manipulated to be, perfectly registered.
The bottom line is that multiple pass scans may reduce noise, but may
also lose sharpness.

 

[Kennedy McEwen]

Thanks, ED. Your product description and site should include this
statement. Even if all the scans are buffered, there is no guarantee
that they will be, or can be manipulated to be, perfectly registered.
The bottom line is that multiple pass scans may reduce noise, but may
also lose sharpness.

I am pretty sure that Ed already does include such a statement, either
on his web site or in the Vuescan user guide. In fact, I seem to recall
reading Vuescan documentation which identified at least one specific
scanner model that was not recommended for multipass scanning because of
this very issue. Its either on the site or in the product guide.

 

[Ivan]

If the snow has been exposed with a simple meter won't it be underexposed
and a bit thin? Assuming it IS correctly exposed, there will be a large
average density, but no particularly dense bits and so no real problem.

I always expose my snow shots for detail in the main subject...grassy
clumps, old rusty machinery, weathered wood. I like the near "bleached"
look in most of my snow scenics.

On my scanner (Canon4000) most colour negs can be scanned OK, but with a
bit of noise in some highlights. eg. a shot into a hazy sun where you
still want to see some detail in the very bright surrounding cloud and
with a couple of stops + compensation to hold foreground shadow detail.
The Vuescan long exposure pass worked well for me on that.

First time I've heard the term "vuescan long pass"....explain please. *S*

The other

times I have used it are on black and white negs with strong highlights
and some overdevelopment.

the old guide: with slides, expose for the highlights, (which is easy in
snow) with negs, expose for the shadows. Both can give a correctly
exposed image which is easy to scan.

yup, that's what I thought...thanks for the seconder.
Ivan

 

[Bruce Graham]

First time I've heard the term "vuescan long pass"....explain please. *S*

Vuescan has an option to make a 2 pass scan where the second pass has a
longer exposure than the second. The 2 images are combined to catch the
dark detail off the long exposure pass (less noise) and the highlights of
the first pass. It is a difficult act and does not always work (Ed
Hamrick does not claim too much for it) but I find it usually works very
well with the Canon FS4000. I have no experience with other scanners.
Note that some scanners can't have their exposure altered, so for those,
the process is equivalent to * 2 multisampling at best.

You mention you expose for the subject, so if (and only if) you see noise
in the snow (I'm assuming negative) long exposure should help. If there
is not a significant level of noise, then save time and potential mis-
registration problems by ignoring multi-pass or long exposure pass.

On the input tab, select advanced options, then 3 from the bottom, check
long exposure pass.