[Digikam-users] [spam detected by bogofilter] Re: canon eos20d and unsharp mask

[Gerhard Kulzer]

Am Saturday 03 February 2007 schrieb Dik Takken:
> On Tue, 30 Jan 2007, Andrew Atrens wrote:
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> >
> > Hi folks,
> >
> > I'm processing raw images captured with my EOS20D ..
> >
> > Canon puts out a quick reference guide for 'tips and tricks for
> > maximum image quality' in which they advise -
> >
> > "Canon EOS digital cameras have an anti-aliasing filter installed on
> > the image sensor.  This filter improves color rendition and
> > practically eliminates moire. The liability  is a slight reduction of
> > sharpness. To reduce the softening effect of the anti-aliasing filter
> > we recommend applying an unsharp mask to the image in Adobe Photoshop.
> > Although there is no such thing as a 'best' setting for all
> > applications, we suggest the following as a starting point"
> >
> > Amount: 300%
> > Radius: 0.3 pixels
> > Threshold: 0 pixels
>
> These settings sound like they would be far too strong for my taste.
> Unsharp masking this strong may greatly amplify sensor noise also...
>
> I would immediately turn off the anti-alias filter, as you can probably do
> things better in software. Also, anything the camera does for you, you
> cannot undo later on.
>
> > I'm noticing that the digikam unsharp mask plugin has a minimum
> > 'radius' of 1 pixel. Which seems more intuitive than '0.3' pixels.
>
> A radius of < 1 pixel does make sense actually, you can use it when a
> setting of 1 pixel is not good enough. Try the GIMP, it can do unsharp
> masking < 1 pixel. Maybe Krita can do this as well. I guess it would be a
> good idea to submit a wish for DigiKam to support this as well.
>
> > And secondly, can someone recommend some general guidelines for using
> > unsharp mask? - Unless I ask the camera to do the sharpening
> > 'in-camera' using 'Parameters' settings, I think I'll need to apply
> > this to every raw photo I take. After staring at a photo for a while,
> > one begins to second guess one's instincts about what settings 'work
> > well' and which ones don't.
>
> It's all a matter of taste, really. Unsharp masking is not always the best
> option, though. Do a search on internet on 'smart unsharp masking' to
> learn how to do it properly.

There is another plugin called 'refocus'. It is the better choice when it 
comes to sharpening, because it's very fine in its recontruction, you really 
gain sharpness, whereas U-mask merely simulates sharpness artificially. I 
recommend using U-mask only for taking away haze by setting it 
to 'amount=0.4' and radius to something corresponding to the percentage of 
the big objects on the image (often 50-80).

Gerhard

> Dik

-- 
http://www.gerhard.fr