canon eos20d and unsharp mask

[Andrew Atrens]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

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

I'm noticing that the digikam unsharp mask plugin has a minimum
'radius' of 1 pixel. Which seems more intuitive than '0.3' pixels.

So I have two questions:

Firstly, do the above PhotoShop setting parameters (roughly) map 1:1
with digikam's unsharp mask parameters?

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.

Thanks,

Andrew.

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.5 (DragonFly)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFFv2ew8It2CaCdeMwRAuVyAKCDyk7lj88MCafmjuFs5FI8gylNpgCfe+JJ
xTM+KZfOVUiFVGobkW2DtHE=
=7VDW
-----END PGP SIGNATURE-----

_______________________________________________
Digikam-users mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-users

[Dik Takken]

On Tue, 30 Jan 2007, Andrew Atrens wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> 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.

Dik
_______________________________________________
Digikam-users mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-users

[Gerhard Kulzer]

Am Saturday 03 February 2007 schrieb Dik Takken:

> On Tue, 30 Jan 2007, Andrew Atrens wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > 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
_______________________________________________
Digikam-users mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-users