Paula said:
Hello all,
I'm going to be embarking on a long project of scanning all my family's
photos (5000+) and was wondering about the scanner. I borrowed my
brother's HP 5500 and it was nice having the autofeed option. Now I'm
reading about the Digital ICE software/hardware option on some scanners
such as the Microtek. Is it worth it?
I don't think that the Mikrotek range have ICE. They have a dust and
scratch removal option, but it is not ICE and works very differently
from it.
ICE is a trade name now owned by Kodak and covers two very specific
methods of defect removal on film and prints.
ICE for film scanning requires that as well as the three colour
channels, red green and blue, the scanner also has an infrared channel.
The dyes used to create the image on most colour films are almost
transparent to the infrared light, so the image in that channel has a
very low contrast monochrome version of the visible image, with every
spec of dust and defect on the emulsion and the film base produced at
full density. This infrared image is then thresholded to eliminate the
image content, leaving just the dirt and defects. Software then masks
the defects in the remaining three visible channels, based on the
locations identified on the infrared channel, by interpolation from the
nearest non-defective pixels. The result is am image which retains all
of the original sharpness and detail for the clean parts of the film but
has replaced the dirt by a close approximation of the local image
content.
The main limitation with ICE is that it relies on the image material
being very transparent to the infrared light. This is fine for all
colour negative film and non-Kodachrome colour slide film. However,
normal traditional silver based black and white film is not transparent
to infrared, so ICE simply does not work at all with this type of film.
This has led a few folk to erroneously conclude that the scanner itself
is not compatible - but they work fine if ICE is switched off. Modern
chromogenic black and white film, which is basically a colour film with
black dye works perfectly however. Somewhere in the middle lies
Kodachrome. This is a completely different colour emulsion that is
basically three individual layers of silver based black and white.
Depending on the batch of emulsion and the Kodak process, more or less
of that original silver remains in the final image. So some KC films
scan perfectly with ICE whilst others are problematic. I have been
lucky since the few Kodachrome films I have all ICEd up nicely, but
others have not fared quite so well.
There are similar alternatives using the infrared channel, for example
Canon's "FARE" and Ed Hamrick's "Infrared Clean" in Vuescan, but they
ICE-like, differing in how the infrared channel is captured and used to
process the image. The performance of these alternatives can be very
similar to ICE itself, indeed some consider them to be better.
ICE for flatbeds scanning prints is also a hardware/software solution
and uses a second light source so that dust and defect on the print
casts a shadow, or rather a different shadow. By comparing the images
using the two light sources, the location of real dirt and defects can
be identified and discriminated from the real image - assuming that the
original image is flat. As with film ICE, this defect mask is then used
to conceal the defects by interpolating data from around them. The
effect is somewhat less successful with textured prints.
I did some searching and found out
that Kodak has a similar plug in for Photoshop. I'm just learning
Photoshop CS and am willing to try anything to make the job less
tedious.
There are lots of alternative dust and scratch filters around - the one
already built into Photoshop works pretty well, and there is the free
Polaroid Dust & Scratch Removal utility which runs stand alone and as a
PS plug-in. Another is available as part of the Silverfast software
package, which I believe is what is offered by Mikrotek. I haven't seen
any offering from Kodak yet, although they do offer the ICE enhancements
in ICE4 (GEM, ROC and SHO) as separate plug-ins, but these do not remove
dust and scratch defects. Full ICE, ICE3 and ICE4 are only available
for integration into scanners by Original Equipment Manufacturers
(OEMs).
The software only clean-up schemes all work on generally the same
principle - apply a special filter to the image to identify what is
*likely* to be dust or a defect and then create a mask similar to the
infrared channel used in true ICE. That really is where they fall down
because, while ICE identifies the dirt and defects directly with minimum
ambiguity with real image information using a special hardware feature,
these filters have to discriminate between defect and original image
based only on the content of the scanned image itself.
Frequently this is achieved by looking for very sharp edges in the
image, using the assumption that the image recorded on the film is
composed of grain or dye clouds and has been focussed by a lens and is
therefore relatively soft at the finest resolution compared to the dust
and defects. However that distinction is blurred (no pun intended) by
the scanner's optics and its limited resolution, so some true detail in
the image is often mistaken for defects while some defects are mistaken
for image content. The only way round this conundrum is to leave the
final decision to the user. Consequently they offer adjustable features
and a preview window so that you can judge just how much or how little
of the dust and dirt you want to leave or how much detail you want to
remove. Suffice to say, nobody has yet designed a filter that has
sufficient discrimination to get one without the other and, since the
assumption is made that a defect is real and sharp, a lot of real image
sharpness and detail is inevitably sacrificed.
Is real ICE worth it? You bet! No software only solution comes
remotely close to the hardware/software combos, of which ICE is the
market leader.
