VueScan: problems with IR cleaning and Velvia 100F

Mac OS X 10.3.1, VueScan 7.6.74, Minolta DSE 5400.

I submitted a problem report to Ed, but I'm wondering if there are
others with the same problem. It seems a problem with the combination
VueScan + DSE 5400 + Velvia 100F but it might occur with other film
types or IR equipped scanners too. I know there are IR problems related
to Kodachrome but this seems to be something different.

With certain slides, VueScan seems to generate faulty IR data to repair
defects that aren't there. I noticed since I started scanning Velvia
100F. I didn't have the problem with other film types (never used
Kodachrome), nor with scanning without IR cleaning. Using the Grain
Dissolver doesn't help either. The problem does not occur with the same
slides and the Minolta Scan Utility. It seems to be an isolated,
reproducible problem with IR cleaning in VueScan only. It does occur
with VueScan 7.6.70, too.

Scanned image, at low resolution, light IR cleaning in VueScan,
converted to sRGB and saved as low-qualty JPEG for the web:
http://www.vandervegte.com/Temp/RGB-IR-cleaned.jpg
Look at the extreme artefacts on the right-hand edge, in the tree.

RGB image from VueScan, no IR cleaning:
http://www.vandervegte.com/Temp/rgb.jpg
(you can switch back between this image and the previous to see the
effect of 'cleaning')

IR channel from VueScan, converted to grayscale:
http://www.vandervegte.com/Temp/IR.jpg

Preview screenshot, rotated, showing IR detect color:
http://www.vandervegte.com/Temp/IRpreviewRotated.jpg
(note that the red area is fuzzy because of the JPEG compression)

My impression is that the IR readouts that Vuescan is using, somehow
seem to be related to data in the film emulsion.

Any ideas?
Thanks in advance for your input.


--

Wilfred van der Vegte.
Replace 'invalid' by my first name to reply by e-mail

"Wilfred van der Vegte" <invalid@vandervegte.com> wrote in message
news:buqk4a$3ln$1@news.tudelft.nl...
> Mac OS X 10.3.1, VueScan 7.6.74, Minolta DSE 5400.
SNIP
> With certain slides, VueScan seems to generate faulty IR data to repair
> defects that aren't there. I noticed since I started scanning Velvia
> 100F. I didn't have the problem with other film types (never used
> Kodachrome), nor with scanning without IR cleaning. Using the Grain
> Dissolver doesn't help either.

If you rotate the slide 180 degrees before inserting it in the scanner, does
the majority of the IR signal still come from the righthand side of the
image? If it does, then it is the lightsource that's uneven, otherwise it's
in the film.

Bart

Bart van der Wolf wrote:

> "Wilfred van der Vegte" <invalid@vandervegte.com> wrote
>
>>Mac OS X 10.3.1, VueScan 7.6.74, Minolta DSE 5400.
>
> SNIP
>
>>With certain slides, VueScan seems to generate faulty IR data to repair
>>defects that aren't there. I noticed since I started scanning Velvia
>>100F. I didn't have the problem with other film types (never used
>>Kodachrome), nor with scanning without IR cleaning. Using the Grain
>>Dissolver doesn't help either.
>
>
> If you rotate the slide 180 degrees before inserting it in the scanner, does
> the majority of the IR signal still come from the righthand side of the
> image? If it does, then it is the lightsource that's uneven, otherwise it's
> in the film.


With another slide, the problem occurred along the short side and also
in more central areas, when scanned in the same direction.
Also, the ICE feature in the Minolta software cleans this slide
flawlessly so I don't think it's the light source.

I agreed to send Ed a raw scan file but I'm afraid I won't have time to
do that today. I will the newsgroup you posted if anything comes out of it.

--

Wilfred van der Vegte.
Replace 'invalid' by my first name to reply by e-mail