difficulty drum scanning negatives

In article , Neil Gould
writes
Recently, Kennedy McEwen posted:

Snipped earlier quotations which can be pulled from the relevant
archives if anyone is interested

That "the numeric data contains various distortions of the
subject" directly addresses the end result of all stages up to the point
where that data can be examined -- e.g. post sampling, and post storage.
It in no way isolates the sampling stage, as exemplified by "...some may
be assignable to the input filtering...", while the last portion refers to
the *implementation*, e.g. "practial limitations of math operations", or
put another way, real-world execution of those functions. Unless you have
access to some device the rest of the world has yet to see, this is an
accurate statement.

Despite all of your subsequent floundering on this Neil your statements
were not clearly referring to sampling "and all previous processes",
especially when you chose to address those earlier process with separate
criticisms. You may mean what you say but, if so, you certainly haven't
said what you mean!

As to the distortion introduced specifically by sampling, pray explain
*exactly* what you mean. You now specify that you are considering
real-world situations, but no real world, high performance scanner
suffers from relevantly significant distortion at the sampling stage.
Quantisation on almost all drum scanners, though not strictly sampling
but I'll include it for your benefit, is sufficient that its associated
noise is lower than the random noise in the film grain itself and
certainly lower than photon noise required to interrogate it. Spatial
positional errors are at least an order of magnitude less than the
aperture size itself and are thus irrelevant. Where and what,
precisely, is this real world sampling distortion to which you refer?

Now, we're getting somewhere. My repeated request was for a
reference to a commonly available machine which has sufficiently
high performance capabilities to reliably avoid grain aliasing with
all commonly available films (obviously, for all subjects and
without sacrificing detail or introducing other artifacts). I am
unaware of the existance of such a scanner, and would appreciate
make and model, or a pointer to the site. If you've already done so,
it isn't on my news service.

Pick any of the currently available film/flatbed scanners and you will
have in your hands a scanner which does not alias grain.

However, in the process, they compromise the image in other ways, and as
such do not meet the criteria that I've spelled out, above in "...for all
subjects and without sacrificing detail or introducing other artifacts".

Look at the Minolta 5400 for a higher resolution scanner which, which
the grain dissolver activated, does not alias grain.

Ditto.

Although not technically a drum scanner, the Imacon 848 provides most
of the related features and will cope with most photographic film
without grain aliasing or resolution loss.

"Most photographic film" is not "all commonly available film", which is
another of the criteria from above.

Finally, its expensive but the Aztek Premier will do 16000ppi optical
sampling with independent aperture control to get everything off the
highest resolution monochrome film without introducing grain aliasing
at all.

I'll look into this model. Thank you for the reference,

As you will note from the above I specifically ramped up the performance
level, at each stage providing a device which addressed the next most
significant point in your list of criteria. It was not my intention
that all of the above would meet all of your criteria, however it
indicates that eliminating grain aliasing does not in itself require a
significantly high performance device.

even if I remain
skeptical that 16000 ppi is sufficiently high frequency to "get everything
off the highest resolution monochrome film" without any artifacts, at
least it's not flatbed territory or CCD-based.

I think you will find that it is capable of much higher sampling if
necessary, however the minimum aperture size is around 3um in diameter
and that defines the limit in terms of the anti-alias spatial filter.
That corresponds to the cut-off of a perfect diffraction limited f/4
lens across the visible spectrum, with considerable contrast reduction
for faster lenses. So even if you can find a film capable of resolving
it, you won't be able to put much information of that scale onto the
film in the first place. Even an optically perfect f/1 lens, and Kodak
Tech Pan developed in fine grain developer will have a composite MTF of
no more than 7% at the critical spatial frequency of that aperture
dimension, and that is just what is present on the film, it doesn't
include any reproduction lens, such as in a projector, enlarger, scanner
or even your own eyes! But you claim you are constraining your comments
to real world situations - well, unless you are prepared to extend your
real world photographic situation into the hard UV or X-ray region then
your concerns about additional information being present on the film are
totally unfounded - and all of this at spatial frequencies below any
that aliasing, whether grain or any other artefact you might be
concerned about, becomes an issue!

Which is the crux of the problem, is it not?

Not really. Most, if not all of the people on this forum, are
interested in scanning images from colour film where such high
resolution requirements just don't exist.

Definitely not "all of the people on this forum", based on the number of
inquiries related to scanning monochrome negatives. You shouldn't have to
search very deeply to find a significant number of such requests.

Furthermore, there are color films that are also challenging to scan, such
as the Kodachromes. I've gotten much better results from optical
enlargements of those slides.

Kodachrome is essentially a 3 layer dyed monochrome emulsion, the
resolution of which is almost an order of magnitude lower than the best
black and white films! However, retaining in some cases a significant
silver content in the developed emulsion it also retains a sharp grain
structure with high spatial frequency content. Nevertheless, the film
has no image resolution at all at 16000ppi, whilst a suitably selected
aperture size will totally eliminate grain aliasing at that resolution.
It may be challenging to scan, but it certainly is not a problem for
even moderate professional scanning equipment. Even decent desktop
scanners, such as some I mentioned in my previous post, can pull almost
everything off of Kodachrome without grain aliasing.

I haven't used NPS 160, as is the case of
the OP, but allow for the possibility that this might be another such
film. Do you know for certain that it isn't?

NPS is a relatively high resolution chromogenic colour negative film
which presents no more problems, in terms of granularity, than other
films of the same type. It's limiting resolution is of the order of
80-125cy/mm, around 1/3rd the highest resolution traditional B&W
emulsions and should present no problems whatsoever to a good drum
scanner. It is possible to get more information on there than can be
reproduced by 4000ppi scanning, but not much. Consequently, the
Crosland drum machine should be capable of getting virtually all of the
image content off without aliasing at all.

However, as was pointed out right at the start of this thread, negative
film requires contrast stretching when producing positive images -
whether by scanning or conventional chemical printing. That enhances
the visibility of the grain on the film much more than would be apparent
from slide film. That is just a problem with all conventional
photographic colour negative films.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

Recently, Kennedy McEwen posted:

In article , Neil
Gould writes
Recently, Kennedy McEwen posted:

Despite all of your subsequent floundering on this Neil your
statements were not clearly referring to sampling "and all previous
processes", especially when you chose to address those earlier
process with separate criticisms. You may mean what you say but, if
so, you certainly haven't said what you mean!

Despite your unbending desire to misrepresent what I wrote, and ignore
clarifications when it suits you, I fail to see how you could possibly not
know what I meant as early as 4/4/04, when I wrote:

"As, to my knowledge, there is no system available that implements perfect
input filtering and flawlessly applies sampling algorithms... "

"The distortion I spoke of is the difference between the subject and the
post-filter representation, and in other parts of the exchange, included
the possibile accumulation of errors due to hardware computational
limitations. I've never claimed differently. "

I clarified what I was referring to in terms that I hoped would be
unambiguous as soon as I realized the miscommunication. And, there still
is no evidence of a "mental model" in any of this.

As to the distortion introduced specifically by sampling, pray explain
*exactly* what you mean.

Did that, several times.

You now specify that you are considering
real-world situations, but no real world, high performance scanner
suffers from relevantly significant distortion at the sampling stage.

I made it clear more than once that I was describing hardware limitations,
and not describing "good performance." To be clear, I agree that hardware
errors introduced at the sampling stage are likely to have the least
impact on the image quality, though they may be multiplicative in
subsequent stages. That's very different than saying such errors don't
exist, which is the position you're clinging to, and my *only*
disagreement with you on that point.

However, as was pointed out right at the start of this thread,
negative film requires contrast stretching when producing positive
images - whether by scanning or conventional chemical printing. That
enhances the visibility of the grain on the film much more than would
be apparent from slide film. That is just a problem with all
conventional photographic colour negative films.

What are you calling the artifact represented by "(enhanced)... visibility
of the grain", above? Perhaps that is a point of miscommunication in this
discussion.

Neil

In article t, Neil
Gould writes

As to the distortion introduced specifically by sampling, pray explain
*exactly* what you mean.

Did that, several times.

Nope - I have seen what you have written and nowhere does a description
of the distortion that you specifically attribute to sampling, having
already attributed some aspects to the input filter, occur. You have
mentioned aliasing however, as already explained, with an appropriate
input filter, such as a properly selected aperture size and shape on a
drum scanner, no such distortion is created. So what is this distortion
you are so concerned about?


However, as was pointed out right at the start of this thread,
negative film requires contrast stretching when producing positive
images - whether by scanning or conventional chemical printing. That
enhances the visibility of the grain on the film much more than would
be apparent from slide film. That is just a problem with all
conventional photographic colour negative films.

What are you calling the artifact represented by "(enhanced)... visibility
of the grain", above? Perhaps that is a point of miscommunication in this
discussion.

The artifact I am referring to is the grain on the film itself, not
aliased grain or distorted grain, simply the grain itself.

Since an image is recorded on colour negative film in a reduced contrast
form, that recorded image must be contrast enhanced for viewing in a
positive form. The grain on the film is also contrast enhanced by this
process at the same time. By comparison, the image recorded on positive
slide film has full contrast. No negatives ever exhibit as dense images
as are present on slides. The up side of this is that viewing the image
or printing from a positive film image requires no contrast enhancement
of either image or grain. The downside is that the exposure latitude -
the range of luminance which can actually be recorded on the film - is
much less for positive slide film than for negative film, and therefore
much more precise exposure is necessary.

Consequently, images from negatives always exhibit more visible
granularity that those from positive film of the same generic standard.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

Recently, Kennedy McEwen posted:

In article t, Neil
Gould writes

As to the distortion introduced specifically by sampling, pray
explain *exactly* what you mean.

Did that, several times.

Nope - I have seen what you have written and nowhere does a
description of the distortion that you specifically attribute to
sampling, having already attributed some aspects to the input filter,
occur. You have mentioned aliasing however, as already explained,
with an appropriate input filter, such as a properly selected
aperture size and shape on a drum scanner, no such distortion is
created. So what is this distortion you are so concerned about?

You may have seen what I wrote, but it apparently didn't communicate. I
explained in several posts that I was referring to hardware calculation
errors. Those errors are distortions attributable to the sampling stage. I
agreed with you that errors at this stage will have the least impact on
image quality in many, if not most cases. Whether this becomes significant
during operations such as contrast stretching due to the mulitplicative
nature of such errors on subsequent stages is an open question. I'm not
concerned about it, just recognizing that such errors exist, and objecting
to your denials of their existance. It's not nearly the big deal that
you've made of it, and certainly doesn't constitute a "mental model" of
any kind.

What are you calling the artifact represented by "(enhanced)...
visibility of the grain", above? Perhaps that is a point of
miscommunication in this discussion.

The artifact I am referring to is the grain on the film itself, not
aliased grain or distorted grain, simply the grain itself.
Since an image is recorded on colour negative film in a reduced
contrast form, that recorded image must be contrast enhanced for
viewing in a positive form. The grain on the film is also contrast
enhanced by this process at the same time.

So, are you saying that the grain is *not* exaggerated (either contrast
range or shape), but accurately represented? If so, this shouldn't be a
problem worthy of conversation. If not, then this can be a problem if it
becomes an issue in prints made from scanned negatives, for example
limiting practical enlargement sizes. Perhaps the same problem that the OP
was trying to describe?

Neil

In article t, Neil
Gould writes

So, are you saying that the grain is *not* exaggerated (either contrast
range or shape), but accurately represented? If so, this shouldn't be a
problem worthy of conversation.

If you go back and read the original post you will see that it certainly
is an issue worthy of conversation.

As you will also note from the first comment I made on this thread, I am
not convinced that the issue raised is *just* one of grain aliasing, in
the main because I know that this is a character of negative film in any
case. However "not just" and "not" are not identities. Whilst, as I
mentioned before, Crosland scanners *should* be capable of recovering
almost all of the information from NPS film without introducing
aliasing, I do not know any more than anyone else writing in this thread
as to how the scan was actually made and whether the scanner was
optimally operated. Therefore grain aliasing cannot be ruled out,
however, even without it, results similar to those reported could be
anticipated.

As I stated in my second post to the thread, the only way to tell for
sure if it is aliased is to compare it to the original, unsampled, slide
or negative - which usually means comparing a full resolution print from
the scanned image to a conventional chemically produced print of the
same size. Differences in granularity between the prints, relative to
the image, would indicate grain aliasing.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

Recently, Kennedy McEwen posted:

In article t, Neil
Gould writes

So, are you saying that the grain is *not* exaggerated (either
contrast range or shape), but accurately represented? If so, this
shouldn't be a problem worthy of conversation.

If you go back and read the original post you will see that it
certainly is an issue worthy of conversation.

Well, no one can claim that it didn't get adequately conversed. ;-)

Sorry, but the early posts on this topic are already scrolled off the
server. However, I didn't get the remotest impression that Jytzel thought
the grain was "accurately represented", and was indeed complaining that it
was not. So, we're actually conversing about the _second_ clause from my
statement (snipped from the excerpt above). ;-)

As you will also note from the first comment I made on this thread, I
am not convinced that the issue raised is *just* one of grain
aliasing, in the main because I know that this is a character of
negative film in any case.

I realize that naming artifacts is something that people generalize about
in every form of media. Many unexpected results having to do with grain
may get called "grain aliasing", when in fact they may be something else
or a combination of artifacts. I don't get hung up by such colloquial
usages.

However "not just" and "not" are not
identities. Whilst, as I mentioned before, Crosland scanners
*should* be capable of recovering almost all of the information from
NPS film without introducing aliasing, I do not know any more than
anyone else writing in this thread as to how the scan was actually
made and whether the scanner was optimally operated. Therefore grain
aliasing cannot be ruled out, however, even without it, results
similar to those reported could be anticipated.

Crossfield scanners aren't the newest kids on the block. It could simply
be that it was out of spec. I'd even suspect that it could be the result
of requesting the wrong resolution scan.

As I stated in my second post to the thread, the only way to tell for
sure if it is aliased is to compare it to the original, unsampled,
slide or negative - which usually means comparing a full resolution
print from the scanned image to a conventional chemically produced
print of the same size. Differences in granularity between the
prints, relative to the image, would indicate grain aliasing.

Ummm... I don't know about this one as an objective measure. Too many
variables. Why not examine the original film under a loupe (or microscope,
if necessary), and compare that to the scanned file? That's what I'd do.

Neil

In article . net, Neil
Gould writes

Sorry, but the early posts on this topic are already scrolled off the
server. However, I didn't get the remotest impression that Jytzel thought
the grain was "accurately represented", and was indeed complaining that it
was not.

Well his post is still on this server and I am sure you can read it
again on any of the archives, such as Google Groups, if you want. In
any case, he wasn't complaining that the grain wasn't accurately
represented - he had been told by the scanner operator that it was and
that negatives always show grain more than slides, which is true for the
reasons I have explained. Jytzel was questioning whether this advice
was factual, suspected that the operator was at fault and wondered what
the how he could obtain the best results from his negatives.

The likely fact is that he probably already has the best scans possible
from that particular film, given it's specification, however he could
try either a chemical print or scanning in a higher performance drum
(such as the Aztek I mentioned earlier or a few others).


Crossfield scanners aren't the newest kids on the block. It could simply
be that it was out of spec. I'd even suspect that it could be the result
of requesting the wrong resolution scan.

Neither are they even close to the best or indeed the most flexible in
terms of operator controls, but they should be capable of pulling almost
everything off of NPS emulsion unless actually faulty.

As I stated in my second post to the thread, the only way to tell for
sure if it is aliased is to compare it to the original, unsampled,
slide or negative - which usually means comparing a full resolution
print from the scanned image to a conventional chemically produced
print of the same size. Differences in granularity between the
prints, relative to the image, would indicate grain aliasing.

Ummm... I don't know about this one as an objective measure. Too many
variables. Why not examine the original film under a loupe (or microscope,
if necessary), and compare that to the scanned file? That's what I'd do.

Because the film is negative and compressed image contrast, on an orange
mask, which mean that the perceptual variable will swamp any actual
differences. The only way of making a valid comparison with a scanned
image is to make a continuous (ie. totally unsampled) print of the
highest quality available at the same scale for direct comparison with a
full resolution print from the scan. It would not be necessary to print
the entire image, indeed, for comparison of granularity, it would be
preferable to print only an area of near uniform tone.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

Thanks for all who responded. I got the scans from the office and they
look horrible. I don´t think it´s grain, ít´s noise, noise, noise!
Colors look posterised with no gradation observed. The histogram shows
no abnormalities however (?) I don't believe the problem is the film,
it's the scan that it's bad. If anybody is interested I can send
portion of the image for viewing.

J

Gordon Moat wrote in message ...
Jytzel wrote:

I sent some negatives and slides to drum scan to have the operator
claim that negatives show more grain in the final scan than slides.

Actually not that unusual an observation. Somewhat depends upon which
films are being compared, since a few transparency films do scan with a
very grainy appearance.

I
used 6x6 Fuji NPS 160, a film has low granularity rating. The other
film I used was E100G slide film.

Kodak E100G should scan substantially better than the Fuji NPS. Be aware
that the print granularity, and transparency film grain index are not
directly comparable numbers. Kodak has a technical document PDF about
this if you want to explore more on that issue.

I find it hard to believe the
operator's claim. It seems that he is doing something wrong. What
could it be and how to get the best scan out of my negatives?
By the way, they use Crosfield drum scanners.

thanks
J

I have not tried the Crosfield for drum scans, though I have noticed
some films need a few tricks to get the best results. Other than the
skill and experience of the operator being in question, you might have a
scan of the negative done as a positive, and reverse it in your editing
software. While I am not sure exactly why that works better, you might
want to give it a try. Be aware that not all film and scanner
combinations react the same, so having it drum scanned on another type
of machine might be a better option.

Ciao!

Gordon Moat
Alliance Graphique Studio
http://www.allgstudio.com

Hi,

Recently, Kennedy McEwen posted:
Neil Gould writes
Ummm... I don't know about this one as an objective measure. Too many
variables. Why not examine the original film under a loupe (or
microscope, if necessary), and compare that to the scanned file?
That's what I'd do.

Because the film is negative and compressed image contrast, on an
orange mask, which mean that the perceptual variable will swamp any
actual differences. The only way of making a valid comparison with a
scanned image is to make a continuous (ie. totally unsampled) print
of the highest quality available at the same scale for direct
comparison with a full resolution print from the scan. It would not
be necessary to print the entire image, indeed, for comparison of
granularity, it would be preferable to print only an area of near
uniform tone.

I understand your concern about the compressed and negative image
contrast. However, I'd be equally concerned about the apparent aliasing
that may be introduced by the reconstructing application; the various
resolutions that can result from different paper choices in the optical
print, etc.

However, for the purpose of establishing grain aliasing, one should only
have to examine the edge of a high-contrast portion of the image under
magnification and compare that to an equivalent zoom magnification of the
digital file (obviously not to the pixel level). If the on-screen profile
matches the optical profile... no aliasing... if they're overly blocky...
aliasing. Why would this method not yield a "valid comparison"?

Neil

Recently, Jytzel posted:

Thanks for all who responded. I got the scans from the office and they
look horrible. I don´t think it´s grain, ít´s noise, noise, noise!
Colors look posterised with no gradation observed. The histogram shows
no abnormalities however (?) I don't believe the problem is the film,
it's the scan that it's bad. If anybody is interested I can send
portion of the image for viewing.

Out of curiosity... have you made an optical print of the film yet? And,
how are you observing the scans?

Regards,

Neil