[Digikam-users] RAW pictures: darkness + saturation

[Sven Burmeister]

Am Dienstag, 24. Juli 2012, 12:50:34 schrieb Elle Stone:
> saturation -S is set using
> (check) Exposure Correction. Shift linear.

If I do not enable that option digikam uses:
Scaling with darkness 0, saturation 4095, and
multipliers 1,707224 1,000000 2,167300 1,000000

If I enable that option and set shift linear to 2.x digikam uses:
Scaling with darkness 0, saturation 4095, and
multipliers 1,707224 1,000000 2,167300 1,000000

If I use dcraw it shows:
dcraw -v -w -S 4000 P1030405.RW2 
Loading Panasonic DMC-LX3 image from P1030405.RW2 ...
Scaling with darkness 15, saturation 4000, and
multipliers 1.707224 1.000000 2.167300 1.000000

Are you sure that linear shift is the correct option?

If so this would fit to my other findings about digikam not actually using the 
values from the demosaicing tool correctly. Its debug information if started 
from a konsole always shows "AHD" even if the amaze algoritm is set. It also 
messes up darkness vs. saturation values.

> I don't think there is a way to set the -k option using digiKam.
> 
> I've experimented and never myself seen any benefit from altering the
> "-k", darkness" value that dcraw calculates. It seems that if you
> change the calculated "darkness" value, you need to "recolor balance
> from the shadow end of the image", so to speak.
> 
> So I am really, really curious what camera/type of image you are
> processing that benefits from altering the dcraw "-k" value. Do you
> have screen shots?

It is one way of getting noise down in dark areas. There might be different 
ways to do so but why should one be restricted when it comes to RAW – the 
whole point of RAW is that you can set all kinds of things to create the 
picture you want.

> Also, does anyone know what digiKam Highlight EV does?

Does not seem to make a difference. :(

Sven