Exposure correction shift(linear) strange behavior

[Pedro Celestino dos Reis Rodrigues]

Hi there

Today, after upgrading some libraries, I found the raw import tool presenting
negative values to the shift(linear) parameter.
I restored a zoero value and the images produced are a lot overexposed.
Up to yesterday, overexposing started near values 1 and 2 of this parameter.
Now this interval is shifted nearly to -1.5 -0.5.
It seems to be doing the correct processing but the values are strange.

Do someone experienced this behavior?

Thanks

Pedro

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[Gilles Caulier-4]

Hi,

If i remember i fixed in the past libkdcraw raw decoding widget in
this way to follow changes from libraw decoder settings...

Gilles Caulier

2013/11/21 Pedro Celestino <[hidden email]>:

> Hi there
>
> Today, after upgrading some libraries, I found the raw import tool presenting
> negative values to the shift(linear) parameter.
> I restored a zoero value and the images produced are a lot overexposed.
> Up to yesterday, overexposing started near values 1 and 2 of this parameter.
> Now this interval is shifted nearly to -1.5 -0.5.
> It seems to be doing the correct processing but the values are strange.
>
> Do someone experienced this behavior?
>
> Thanks
>
> Pedro
>
> _______________________________________________
> Digikam-users mailing list
> [hidden email]
> https://mail.kde.org/mailman/listinfo/digikam-users

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[Pedro Celestino dos Reis Rodrigues]

Hi,

Thank you very much for your prompt answer!

I can now provide some additional info. I was reading libraw manual and I
found this entry:


*int exp_correc; float exp_shift,exp_preser;*
Exposure correction before demosaic.


     *  exp_correc: positive value turns the feature on (default: off).
     *  exp_shift: exposure shift in linear scale. Usable range from 0.25
(2-stop darken) to 8.0 (3-stop lighter). Default: 1.0 (no exposure shift).
     *  exp_preser: preserve highlights when lighten the image. Usable range
from 0.0 (no preservation) to 1.0 (full preservation). 0.0 is the default
value.

I supose that it corresponds to the parameters in the Exposure Correction
section of digikam "raw import tool configuration", as the image at
http://userbase.kde.org/images.userbase/1/11/WhiteBalance.jpg suggests.

If I understood it correctly, it says that the neutral value (no exposure
shift) should be 1.0, not something like -1.5 as it is being now. Moreover,
it says that the values should allways be positive (min 0.25 and max 8.0)

I think that the behavior changed after upgrading libkdcraw22 from version
4:4.10.5 to 4:4.11.3-1. May it be relevant, I can try to downgrade to
confirm this.

Thank you for the great work

Pedro


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[Pedro Celestino dos Reis Rodrigues]

Hi Gilles,

Thank you very much for your prompt answer!

I can now provide some additional info. I was reading libraw manual and I
found this entry:


*int exp_correc; float exp_shift,exp_preser;*
Exposure correction before demosaic.


     *  exp_correc: positive value turns the feature on (default: off).
     *  exp_shift: exposure shift in linear scale. Usable range from 0.25
(2-stop darken) to 8.0 (3-stop lighter). Default: 1.0 (no exposure shift).
     *  exp_preser: preserve highlights when lighten the image. Usable range
from 0.0 (no preservation) to 1.0 (full preservation). 0.0 is the default
value.

I supose that it corresponds to the parameters in the Exposure Correction
section of digikam "raw import tool configuration", as the image at
http://userbase.kde.org/images.userbase/1/11/WhiteBalance.jpg suggests.

If I understood it correctly, it says that the neutral value (no exposure
shift) should be 1.0, not something like -1.5 as it is being now. Moreover,
it says that the values should allways be positive (min 0.25 and max 8.0)

I think that the behavior changed after upgrading libkdcraw22 from version
4:4.10.5 to 4:4.11.3-1. May it be relevant, I can try to downgrade to
confirm this.

Thank you for the great work

Pedro



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[hidden email]
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