Gamma in HDR together with ICM

[theo]

Hi,

I observe a behavior of HDR which I do not quite understand:

I have a computer generated tif file (based on IT-8 data) which
has a profile assigned. The gamma with which the file was generated
was 2.2 (just as side information).

One specific patch (to which I will refer later) has the following
value:
RGB: 132,130,128
Lab: 53,-4,5

When I convert the file to AdobeRGB profile (in photoshop) the patch becomes:
RGB: 138,142,132 (rendering intend: perceptual)
Lab: 59,-4,5

When I assign the AdobeRGB profile (in photoshop) the patch becomes:
RGB: 132,130,128 (no change because profile is just assigned)
Lab: 55,1,2


Now I open the file with HDR and have the following configuration in
options of HDR:
gamma: 2.2
gamma in HDR: 2.2
CMS Scanner->Intern: None
Intern: AdobeRGB

The upper patch becomes:
RGB: 132,135,126
Lab: 55,1,2

I expected this, it is like asigning a profile in photoshop, therefore
the same RGB but different Lab values.

With gamma: 1.0 and gamma in HDR: 1.0 I get the same.

I expected also this, becaus I assume as long gamma and gamma in HDR
have the same value that both have no influence.

Now I change the options to:
gamma: 2.2
gamma in HDR: 2.2
CMS Scanner->Intern: Embedded profile
Intern: AdobeRGB

I would now expect to get the same behavior as with converting to
the AdobeRGB profile in photoshop.

But I get for the patch:
RGB: 84,87,78 !!!!
Lab: 27,-5,6

This is way off.

If I change gamma and gamma in HDR to 1.0 (both) I get:
RGB: 137,141,131
Lab: 58,-4,5
which is just a little bit off the photoshop conversion (may be the different
Engine).

My question is why is the behavior with embedded profile different
between the two gamma configurations?

[LSI_Muenier]

Dear Theo,

your problem might be related to the bugfix I just made in SilverFast.
Please send me your image file (the original one with your ICC profile embedded) by email.
I can then check this and eventually send you a bugfixed version back.

Best regards,
Martin Muenier

[LSI_Muenier]

Here's the email address: martin.muenier@silverfast.com