Are my raw scans okay?

[Jack Frillman]

When I save a raw scan (Vuescan & Minolta 5400) and view it with Vuescan
it looks like I just did a scan from the scanner. When I open the same
raw scan with GIMP the image is very translucent and you can see the
checker board background. In fact the checkered board background
dominates the image. On a scan I made of a solar eclipse there is no
image at all when opened with GIMP but I see the image fine with
Vuescan. In GIMP I even tried to change the contrast, brightness and
other manipulation thingys but I cannot see the image.

Is this normal for these raw scans to be so translucent or did I botch
something up when making the raw scans?

 

[Leonard Evens]

When I save a raw scan (Vuescan & Minolta 5400) and view it with Vuescan
it looks like I just did a scan from the scanner. When I open the same
raw scan with GIMP the image is very translucent and you can see the
checker board background. In fact the checkered board background
dominates the image. On a scan I made of a solar eclipse there is no
image at all when opened with GIMP but I see the image fine with
Vuescan. In GIMP I even tried to change the contrast, brightness and
other manipulation thingys but I cannot see the image.

Is this normal for these raw scans to be so translucent or did I botch
something up when making the raw scans?

I assume that by "raw" you mean that you chose "none" as the color
option. I have used Vuescan with the Gimp under Linux for a while now.
I don't do raw scans because I find the other options more useful.
But I just tried it with a Minolta SD IV with "none". What I saw in the
Gimp was exactly what I saw in the Vuescan scan (and preview) window.

Are we talking about the same thing? I would guess that you have
something set wrong either in Vuescan or the Gimp.

 

[Bart van der Wolf]

SNIP

Are we talking about the same thing? I would guess that
you have something set wrong either in Vuescan or the Gimp.

Maybe the additional IR channel in VueScan's Raw triggers the Gimp
into believing it's a transparent channel while it's a mask, so not
something to visualize.

Bart

 

[Jack Frillman]

I assume that by "raw" you mean that you chose "none" as the color
option. I have used Vuescan with the Gimp under Linux for a while now.
I don't do raw scans because I find the other options more useful. But
I just tried it with a Minolta SD IV with "none". What I saw in the
Gimp was exactly what I saw in the Vuescan scan (and preview) window.

Are we talking about the same thing? I would guess that you have
something set wrong either in Vuescan or the Gimp.

By raw I mean saving the data that comes off the scanner with no
processing as described in the Vuescan documentation.

As for GIMP I just open the raw tiff files just like I do everything else.

 

[Leonard Evens]

By raw I mean saving the data that comes off the scanner with no
processing as described in the Vuescan documentation.

Sorry. I've only used raw once before, and I had forgotten about it.
But this time I used raw with the Minolta SD IV, and I got just what I
expected in the Gimp. No grid pattern showing through.

 

[Dierk Haasis]

Sorry. I've only used raw once before, and I had forgotten about it.
But this time I used raw with the Minolta SD IV, and I got just what I
expected in the Gimp. No grid pattern showing through.

Just to clear that up, as Bart asked, could it be you saved RAW 64bit,
which includes the IR-channel?

 

[Jack Frillman]

Just to clear that up, as Bart asked, could it be you saved RAW 64bit,
which includes the IR-channel?

Not sure but after reviewing the default options I would have to say
they were saved as 48 bit RGB. I do know that I did not change this
option. But then I was able to apply IR clean to raw scan.

When I open with Gimp I get this message.

Warning:
The image you are loading has 16 bits per channel. GIMP can only handle
8 bit, so it will be converted for you. Information will be lost because
of this conversion.


Once I get the house put back together I will try saving in each mode
and see what happens.

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[Jack Frillman]

Just to clear that up, as Bart asked, could it be you saved RAW 64bit,
which includes the IR-channel?

As it turns out the automatic setting will save the raw scan as a 64 bit
RGBI. I did four scans and these are my results. Note these scans were
of a color negative of a total solar eclipse. Therefore the background
would be black when viewed as a postive.

RAW saved format As seen in GIMP
---------------- ---------------
16 bit infrared Frame is all black
64 bit RGBI Only see checkered background
48 bit RGB See image but background is greenish
24 bit RGB See image but background is pale greenish

I determined that the auto setting saves in 64 bit RGBI by comparing the
file sizes.

It looks like this validates what Bart suggested. Now what I can't
figure out is the results of the 16 bit infrared.

BTW: What format do folks usually save the raw scans as?

 

[Bart van der Wolf]

SNIP

It looks like this validates what Bart suggested. Now what I can't
figure out is the results of the 16 bit infrared.

It should be used as a mask, marking the defects.

BTW: What format do folks usually save the raw scans as?

I save it as 64 bit/pixel (four 16-bit channels), but while it works
with Photoshop, it apparently could cause the issues you've
experienced in the Gimp.

Bart

 

[Jack Frillman]

SNIP



It should be used as a mask, marking the defects.

Okay. Being new to this I now have to ask. How do you do that?
Or a pointer to some reading material.