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Remove halos

Javier González 

Full member
Joined in August 2009
Posts: 21
Posted 5 November 2011 - 23:10 CET

Emanuel,

Photo uploaded is the equalized version, I think the most important is to see if in the normal pic there are halos visible or not. To me equalized version is not too bad.

In general if shadows removed then more halos, + contrast then + halos.

Javier

Darryl Morrell 

Full member
Joined in August 2008
Posts: 143
Posted 5 November 2011 - 23:34 CET

halos generally mean overproccessed photos, try to go easy on the shadows and highlights tool for one, that helps

Wallace Shackleton 

Full member
Joined in February 2007
Posts: 1897
Posted 6 November 2011 - 05:52 CET

Halos are cause by the sharpening routine.

Sharpening works by boosting the local contrast say between a white fuselage and a black registration, this boosting generates an edge between the black and white. If it is done right then the edge blends with the white, if no then you get a halo or the edge breaks up and looks rough.

Shoot RAW with no in camera sharpening (Canons Standard and Landscape Picture Styles DO add sharpening to the images), JPEGs will add a degree of sharpening as they will process the image in-camera.

Only apply sharpening at the very end of your work flow and if all else fails and you do get a halo or a jagged line use a selective sharpening routine. There are more ways that Unsharp Mask to sharpen an image. The use of a Layer Mask is not difficult.

I use Lab mode and High Pass Filter to do my sharpening. there is a tutorial on the old forum if you are interested.

http://forums.airplane-pictures.net/index.php?/topic/665-high-pass-sharpening/

Paul Nichols 
Full member
Joined in February 2008
Posts: 73
Posted 14 November 2011 - 17:49 CET

Wallace, generally those kind of halos seen in digital images very definitely aren't caused by sharpening (although having too large a radius for the size image you're working on can 'soften' rather than sharpen).

Emanuel, what you're seeing there is possibly an effect of applying rather severe noise reduction. As with excessive Curves adjustments sometimes NR processing can compress information in a photo enough to show posterizing in the upper mid tones and highlights, where more information is required to show smooth details (the distinct bands of colour you can see where information has been lost and tonal changes are sudden rather than smooth are an example of this effect). Once visible they can't be removed, so the trick is to avoid them in the first place. That effect won't have been on the original image that left your camera whether you were shooting RAW or JPEG, so perhaps try re-editing but going a little easier on the noise reduction. It's quite a fine line between getting the best quality you can and overdoing it, so sometimes it's best to tolerate a little noise but retain the detail than it is to try eradicate noise altogether at the expense of another aspect of quality.

Hope that helps :)

paul

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