Re: [UFRaw-Devel] Exposure/film boost idea

[Pascal de B. <pmj...@pc...>]

On Tue, Nov 16, 2010 at 5:33 PM, Bruce Guenter <br...@un...> wrote:
> Hi.
>
> I have found at times that I want to use the exposure adjustment in both
> the digital and film modes at once.  That is, to adjust the exposure
> part way with the digital mode and then boost it a bit in film mode.  I
> wrote the attached patch that splits the adjustment into two parts.
>
> Does this approach make sense?  Should the boost adjustment go somewhere
> else in the UI?  Would another name for it make more sense?
>
> As a side note, part of the desire for the adjustment comes from a bug
> in developing raws from my Sony A700.  To match the output from the
> camera I need to apply a base adjustment of +1.0.  That is, the
> effective dynamic range used by the camera is half of the actual range
> produced by the sensor.  AFAICT ufraw has no way of handling this kind
> of internal doubling, but I'd love to be proven wrong, as it's a real
> PITA to need to boost everything before even starting to tweak things.

I'm pretty sure this is not really how it works...

To "match" camera output there two things to be minded...

First some camera's _seem_ to apply digital exposure correction to
their JPEGs, which is a dynamic correction. So it's hard to compensate
for this without full access to the MakerNotes (if the camera even
stores this in EXIF).

But more importantly:

A consistent difference in exposure, is usually not a difference in
exposure, this is usually just a basecurve difference. In UFRaw you
can emulate this either by fiddling with gamma/linearity, or by making
a nice basecurve for your camera...

I while back I did a basecurve for my Canon, like so:

  http://files.pcode.nl/ufraw/CanonEOS.curve

However, I do not remember which other settings I used it with, so out
of the box this will likely not work for you... The the general shape
of the curve should be okay, so with some curve surgery (keeping the
general shape), you should be able to match your camera pretty well.
Do remember to test your basecurve with lots of differently exposed
images to get a generally usable basecurve.

Regards,
Pascal de Bruijn


Regards,
Pascal de Bruijn