VueScan raw archive scans and rotation

[PackRat]

I have an "is it safe or is it dangerous?" question:

Using VueScan, I have created archival raw TIFF scans of an old book.
In order to get good edge alignment, I flipped the book one way and then
the other when scanning, resulting in all the even pages being right
side up and the odd pages upside down when the raw TIFF files are viewed
sequentially in an image editor/viewer.

I'd like to get all the raw TIFF images to have the same orientation, if
possible. I know that you shouldn't alter the "archival" image in any
way (brightness, black/white points, sharpening, etc.), doing that
instead when scanning from the raw TIFF file and/or in subsequent image
editing (e.g., Photoshop Elements, etc.).

However, can an "archival" image be *rotated* (180 degrees, in this
case) in an image editor, saved back, and still be used by VueScan as a
scannable raw TIFF file with the same "archival" quality characteristic
as the original? (That is, can it replace the original as an identical
substitute?)

Basically, I'm wondering whether a rotation in an image editor (since
VueScan doesn't do this--wish it did!) is a "safe" operation on an
original archival image, or whether it is "dangerous" in the sense that
the image has been altered in some way during the rotation. It seems as
if a rotation ought not change the pixels in an image in any way.

Another way of looking at the question: is it "safe" to rotate an
archival raw TIFF image in an image editor (and consider the rotation as
identical to the original), or must rotation wait until after scanning a
raw file into the "final" TIFF production version image, which has been
adjusted via brightness, histogram, etc., in VueScan and any other
visual adjustments in an image editor?

By the way, to make it absolutely clear, the "rotation" I'm referring to
is not the VueScan input view (flip, left, right, none), but a permanent
change in the order of the pixel arrangement in an image file.

Thanks for any advice you can share!

Harvey

[shAf]

PackRat writes ...
Such questions can be answered by your own experimentation, if you first
create a copy of the original file.

Post by PackRat
...
Basically, I'm wondering whether a rotation in an image editor (since
VueScan doesn't do this--wish it did!) is a "safe" operation on an
original archival image, or whether it is "dangerous" in the sense that
the image has been altered in some way during the rotation. It seems as
if a rotation ought not change the pixels in an image in any way.

I have done this, even to the point of cropping the raw file. It seems Vs
needs only the RGB data, in any form or shape.
--
cheerios ... shAf :o)
Avalon Peninsula, Newfoundland
www.micro-investigations.com

[Bart van der Wolf]

"PackRat" <***@anet.com> wrote in message news:***@4ax.com...
SNIP

Post by PackRat
Basically, I'm wondering whether a rotation in an image editor (since
VueScan doesn't do this--wish it did!) is a "safe" operation on an
original archival image, or whether it is "dangerous" in the sense that
the image has been altered in some way during the rotation. It seems as
if a rotation ought not change the pixels in an image in any way.

It depends on the software used, but rotation angles that are an exact
multiple of 90 degrees SHOULD be lossless, because there is no interpolation
involved. If the software does interpolate (which it shouldn't) then I
suggest getting better software.

Now, assuming a lossless operation, it seems that VueScan is indifferent to
the orientation of the data in its Raw file. So unless Ed Hamrick has a
different view, you should not lose any data after opening a Raw data file,
rotating its data 180degrees, and re-saving as a TIFF again.

The file size might be different after compressing, depending on differences
in compression methods, but the data itself is unaltered. This also allows
you to store the file in its most economical orientation, because it makes a
difference to the storage overhead (column/row pointers) if you store in a
"Landscape" or a "Portrait" orientation. With a large number of files it
might be beneficial enough on storage space and the associated
administration, to spend a little time on that.

Bart

[Ed Hamrick]

Post by Bart van der Wolf
Now, assuming a lossless operation, it seems that VueScan is indifferent to
the orientation of the data in its Raw file.

That's correct - any sort of TIFF file is fine, rotated any way
you'd like.

The only thing to be careful of is to not change the number
of bits per sample - if you read 8-bit samples, write 8-bit
samples and if you read 16-bit samples, write 16-bit samples.

Regards,
Ed Hamrick

[Ed Hamrick]

In other words, is
the re-scan (from a file) completely independent of the original
scanner?

This is mostly true, with one small exception.

The "Input|Scan mode" option tells VueScan what kind of scanner
the raw scan file came from. VueScan doesn't care what the
dimensions of the raw scan file are, but it needs to know:

1) how to transform from the raw colors to other color spaces
2) whether the scan used transparent media or reflective media
3) what type of infrared channel is used (i.e. Nikon, Minolta, Avision,
Canon)
4) the CCD exposure time ratios for color negative film

All of these things are derived from "Input|Scan mode" when
scanning from a raw file.

Regards,
Ed Hamrick