Peripheral image sharpening

[Beep6581]

Originally reported on Google Code with ID 2658

This is a new feature request to implement a peripheral image sharpening to compensate
for peripheral softness of most lenses. Normally, lenses deliver highest level of sharpness
in the center and that sharpness is gradually degrading further from the image center.
The expected output of this tool should be mostly uniform sharpness of the entire image.

In particular, this is important for subsequent image stitching where overall uniformity
of the image sharpness is important.

The UI tool should allow user to draw a flat-type curve. the horizontal axis should
correspond to the length of image diagonal, and the vertical axis to opacity of the
effect.

This tool could be added as additional modulation to the existing RL/USM sharpening
toolset or contrast by detail levels (which would also allow peripheral contrast improvement).

Reported by michaelezra000 on 2015-02-04 19:08:15

[Beep6581]

One technical problem BTW: the more tilted the image is (i.e. the more correction will
be applied to it), the more different treatment does it need.

I guess that you are talking about "big radius sharpening", not just "sharpening".

Reported by pinhuer on 2015-02-07 19:49:28

[Beep6581]

The treatment should be gradually increasing away from the center. I am not yet sure
if this  can be taken care of via opacity/strength alone or whether sharpenning radius
should be also gradually increasing.

The CA correction might already have a method of gradual application of the CA correction
effect as function of distance from the image center... need to look.

Reported by michaelezra000 on 2015-02-07 20:13:25

[Beep6581]

I guess that you do not follow.

Stitching pano without geometry correction is one thing. Adding geometry corrections
makes things more complex.

Reported by pinhuer on 2015-02-08 10:56:33

[Beep6581]

Nice idea.

I don't know too if we need to modify the radius or the strenght, or both, but since
the blur circle increase in the borders i think the first will be the radius.

Isn't there a software that already does this? Iirc dxo?

I think it could be also nice to be able to enter the % of sharpness of the lens relative
to center for borders and maybe corners (i'm thinking about copying the values from
official mtf or serious reviews) so that the curve will be automagically interpolated.

E.g. almost always 100% for center, and let's say 60% for borders and 45% for corners
for a wide angle, 100% for center and 80% for corners on a tele macro.

A sort of database of per lens values (depending on aperture) could also be interesting.

Reported by fotogiuliopv on 2015-02-08 12:28:13

[Beep6581]

Reported by entertheyoni on 2015-02-17 08:07:11

• Labels added: Component-Tool
• Labels removed: 4.3, Component-Quality