Lens aberration ?

[Tony W]

Playing with some holiday snapshots from a few years back and decided to convert this one to B&W. During sharpening noticed light and dark fringeing around objects.

1st pic original jpeg 2nd and 3rd 200% mag last one B&W conversion after tedious cloning to minimise the fringes and rid the image of distractions.

I am not sure what I am looking at here - could it be chromatic aberration or in camera sharpening effect (Fuji Finepix E550) or something else?

[Kraellin]

i could be wrong, but that looks like reflective fringing. it's light from the surrounding area reflecting off the various objects.

nice b&w!

[SilvaFox]

Looks like unsharp masking. You stated "during sharpening..." Was it before, or after?

[Tony W]

Thanks Craig not experienced this type of fringe before and had not heard of reflective fringing.

SilvaFox I fairly sure that the first image is the untouched original jpeg straight from camera. I only noticed the fringes when I sharpened a duplicate during the B&W conversion then went back to the original to look at the problem in more detail.

Attached is a section of another image taken on the same day. As you can see to the left side of images there is a muddy green fringe and on the opposite side a lighter cyan / blue fringe.

[steverd]

Hey its really nice!!!!!!!!

[SilvaFox]

Chromatic Aberration can be fixed in Camera Raw. (if you have the raw.)

I recently fixed this in an image by selecting a single channel and nudging it independently. I know. Sounds like a recipe for disaster but it worked.

[Chain]

My answer: both.

To me the weak cyan/red (colored) fringing on the statue looks like Chromatic Aberration. You can try to compensate for this in Camera Raw (it can process jpegs), or using Filter > Distort > Lens Correction in Photoshop.
(Note in CS5 the lens correction filter has been redone and apparently improved a lot).

Also, it appears that the camera has added some sharpening on top - this would be considerably harder to remove. Anyone got ideas for some smart filtering technique to "undo" sharpening?

Edit:
* Correcting for Chromatic Abberation will require you to work on the un-cropped image for a good result.
* I tried (naively) to simply blur the edges a bit with gaussian blured copy (radius like the halos). The mask i made using a sharpened copy (radius like the halo) - difference blended with the original. Turned into mask (selected the RGB-channel), auto-leveled and blurred a bit. It did help in reduce the halos, but it might loose you some details on other high-contrast areas besides the halos (but could be masked manually)... When I then applied 2 px sharpening on top of everything I ended up with weaker halos then the original, but sharper details. Worth a try perhaps...
* If we can't figure out how to conveniently reduce the halos, you could just use a mask on your new sharpening to make it not sharpen the troublesome areas/edges.

[Tony W]

steverd Thanks

SilvaFox Unfortunately this was a borrowed camera and I did not realise that it could be set to RAW (had a 'Duh' moment when I did find out!). Your 'recipe for disaster' sounds interesting

Chain Your answer of both seems very feasible. Did try to correct the jpeg image in Camera Raw and Lens correction filter in PS without much success.

In the end I resorted to a heavy blunt instrument and used the clone tool, found that Darken and Colour modes worked best although it did leave some 'jaggies'.

Thank you all for your input here

Edit Chain just seen your edit. Thank you very much for detailed explanation as you say might be worth a try. I would also be interested if anyone does have a technique to undo sharpening of this type. BTW, the first image is the full uncropped original - the last image is me just adding a little information as I wanted to keep the boat looking correct on the right hand side