Vuescan raw files saved "at save" have altered color balance.

[Mendel Leisk]

From the Vuescan Help File:

"Raw output with:

If set to "Save", it's written at the same time as other files are
written (i.e. after a scan completes or when the "Save" button is
pressed). In this case, the raw file has had infrared cleaning and
grain reduction applied."

Well, apart from these two filters being applied, the damn color
balance shifts.

If I do a scan-from-disk from a 16bit linear file output through
Minolta Scan Utility, and output a new Vuescan Raw File, "at scan", it
is identical in color balance to the source. If however, I output the
new Vuescan Raw File "at save", the color balance of the raw file
shifts. It is very easy to verify. Just output raws in both ways, from
the same source file, and compare.

Why, I don't know, or really care. It could be the ICC profile I'm
apply to (only, I thought) the finished file. Or the manual color
balance settings, again only supposed to apply to the finished files. I
do know Vuescan has toasted another couple of months worth of my
scanning project, on top of the 3~4 months lost to it's inferior
downsampling algorithm.

I vaguely recollect this was discussed here before. Is this the case?

 

[Steven]

Well, apart from these two filters being applied, the damn color
balance shifts.

I'm not sure if this is relevant but since real-time display of the
preview was introduced (8.2 I think) I've noticed that the preview looks
okay while the preview scan is in process but as soon as it is complete
the display changes and looks considerably worse. I am using 'image'
mode with no colour balance (everything off) so I'm not sure why the
display changes.

-- Steven

 

[Mendel Leisk]

I'm not sure if this is relevant but since real-time display of the
preview was introduced (8.2 I think) I've noticed that the preview looks
okay while the preview scan is in process but as soon as it is complete
the display changes and looks considerably worse. I am using 'image'
mode with no colour balance (everything off) so I'm not sure why the
display changes.

-- Steven

The version I've been using throughout is 8.1.29. Should have
mentioned.

 

[John]

"Raw output with:

If set to "Save", it's written at the same time as other files are
written (i.e. after a scan completes or when the "Save" button is
pressed). In this case, the raw file has had infrared cleaning and
grain reduction applied."

Well, apart from these two filters being applied, the damn color
balance shifts.

If I do a scan-from-disk from a 16bit linear file output through
Minolta Scan Utility, and output a new Vuescan Raw File, "at scan", it
is identical in color balance to the source. If however, I output the
new Vuescan Raw File "at save", the color balance of the raw file
shifts. It is very easy to verify. Just output raws in both ways, from
the same source file, and compare.

Why, I don't know, or really care. It could be the ICC profile I'm
apply to (only, I thought) the finished file. Or the manual color
balance settings, again only supposed to apply to the finished files. I
do know Vuescan has toasted another couple of months worth of my
scanning project, on top of the 3~4 months lost to it's inferior
downsampling algorithm.

I vaguely recollect this was discussed here before. Is this the case?

I have found a thread called "VueScan raw file is not a true raw file!" (Jan
21 2004) where this issue was discussed (incidentally, you were one of the
participants so this may not be news). The thread digressed and meandered
somewhat so it is a little tricky to follow. I gather the conclusion was
that if an ICC profile was selected (as opposed to Built-in) it gets applied
to the raw file in addition to Infra red and grain reduction in the case of
'Raw Output with Save' - although Ed Hamrick categorically said it didn't.
Henk de Jong did some tests and proved it and I think Erik Krause was of the
same opinion. Ed Hamrick seemingly declined to confirm or deny it, at least
in that particular thread.

 

[Mendel Leisk]

I have found a thread called "VueScan raw file is not a true raw file!" (Jan
21 2004) where this issue was discussed (incidentally, you were one of the
participants so this may not be news). The thread digressed and meandered
somewhat so it is a little tricky to follow. I gather the conclusion was
that if an ICC profile was selected (as opposed to Built-in) it gets applied
to the raw file in addition to Infra red and grain reduction in the case of
'Raw Output with Save' - although Ed Hamrick categorically said it didn't.
Henk de Jong did some tests and proved it and I think Erik Krause was of the
same opinion. Ed Hamrick seemingly declined to confirm or deny it, at least
in that particular thread.

Thanks John, that is the thread. I did just calibrate my scanner with
IT8 targets, and set an ICC profile. Could be the culprit. Though it is
NOT supposed to be applied to raw output. Live and learn.

 

[Henk de Jong]

In July 2004 Ed has responded to my problem.
You can read it in the thread at the bottom of this message.

With kind regards,
Henk de Jong


http://www.hsdejong.nl/
Nepal and Burma (Myanmar) - Photo Galleries


-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-

Hi Henk,

Sorry it's taken me so many months to get back to you on this,
but I found out why the two raw files were different.

It turns out that the "Color|Scanner color space" option affects
the raw image data when "Output|Raw output with" is set to
"Save". VueScan produces profiles that attempt to correct for
a non-linear CCD response, and the scanner profile can have
a gamma between 0.95 and 1.05. This non-linearity
correction is being done on the data before being written with
the scan.

It's best to save the raw file at the same time as the scan.

Regards,
Ed Hamrick

P.S. This message is the oldest one in my mailbox, but I didn't
delete it because I was curious why this happened.

Dear Ed,

Thank you for coming back on the issue.
In the end my conclusion was right: "VueScan raw file is not a true raw
file" under the condition that you save the raw scan file with the option
"Output|Raw output with" is set to "Save".
It took me a long time and experimenting to discover when I produced the
right raw file and when the wrong. Fortunately I had not archived any wrong
raw file slide scan

It's best to save the raw file at the same time as the scan.

Yep, that is my current work flow! ;-)

But are you going to do anything about it?
A warning in the help files maybe or are you changing the way the raw files
are saved? After all a raw file is a raw file...

I will remove my scan samples from my website now they are not needed
anymore.

With kind regards,
Henk de Jong