techniques for removing fringing?

Hi all,

I am wondering if anyone can suggest a way of removing fringing from an
image. I shot this picture, http://lim.nl/dockworker%2020060403.jpg,
with the sun behind me, yet it was a very hazy day and I see notable
cyan and purple fringing on the left and right sides resp. of the
statute against the sky. Although I use gimp, photoshop techniques are
welcome, as I can probably emulate them in the former.

Thanks.

--
Colin Brace
Amsterdam

Colin Brace wrote:
Hi all,

I am wondering if anyone can suggest a way of removing fringing from
an image. I shot this picture,
http://lim.nl/dockworker%2020060403.jpg, with the sun behind me,
yet it was a very hazy day and I see notable cyan and purple fringing
on the left and right sides resp. of the statute against the sky.
Although I use gimp, photoshop techniques are welcome, as I can
probably emulate them in the former.

Thanks.

Paint Shop Pro has an effective "CA Reduction" function built in.

Works for PF as well as CA.

David

Colin Brace wrote:

Hi all,

I am wondering if anyone can suggest a way of removing fringing from an
image. I shot this picture, http://lim.nl/dockworker%2020060403.jpg,
with the sun behind me, yet it was a very hazy day and I see notable
cyan and purple fringing on the left and right sides resp. of the
statute against the sky. Although I use gimp, photoshop techniques are
welcome, as I can probably emulate them in the former.

Thanks.

--
Colin Brace
Amsterdam

I can never get the prest Paintshop thing to work, but some time ago I
found this method and this works for sure. Remember though to watch
how you use the saturation slider, as although they look identical
sometimes the fringing is a slightly different hue so it's worth
trying different setting for different pics. This is exactly as i
copied and pasted from somewhere on the web :O)
------------------------------------------------------

a faster and better way — the Hue/Saturation/Lightness (HSL) tool. For
details see the May 2003 Graphics column (available online here),
which covered some of the hidden tricks of this under-used feature.

Instructions for using HSL to remove purple fringing will vary
slightly between programs, but they all follow the same basic process.
Start by loading up your affected image. Now go to the HSL tool. In
Photoshop, select Image-Adjustments-Hue/Saturation… In Photoshop
Elements 2, select Enhance-Adjust Color-Hue Saturation… and in Paint
Shop Pro 8 Adjust-Hue & Saturation-Hue/Saturation/Lightness.

Here is the important step: click the blue channel. Do not adjust the
master channel. Now adjust the saturation slider to around 80 per cent
(you can fine-tune this later).

If you are using Paint Shop Pro 8, move the colour wheel slowly around
and watch the preview window. When you hit the right spot, the purple
will vanish. Fine-tune the slider for maximum effect and click OK. If
there are still traces of purple, repeat the process until you find
the other tone.

The Adobe products take guesswork out of the HSL adjustment step. When
the blue channel is selected, the eye dropper tool will become
available. Click the eyedropper on the left and use it to sample the
purple fringe in your image. You can use the colour slider at the
bottom to make finer adjustments (tip: you can also use the + and -
keys to zoom in and out of the image while the HSL window is still
open).

Finally, you may find the image needs some minor tinkering and will
probably appear a little washed out. Making fine adjustments to the
Brightness/Contrast or Levels settings will correct these problems
---------------------------------------------

--
Paul (Everyone I know goes away in the end)
-------------------------------------------------------
Stop and Look
http://www.geocities.com/dreamst8me/

Colin Brace wrote:
with the sun behind me, yet it was a very hazy day and I see notable
cyan and purple fringing

I'm wondering: why cyan and purple? They're not complementary
colors or anything...something to do with the properties of the sensor?
I know about chromatic aberration, which would seem to explain purple,
but I don't get cyan.

--
Oh to have a lodge in some vast wilderness. Where rumors of oppression
and deceit, of unsuccessful and successful wars may never reach me
anymore.
-- William Cowper

I'm wondering: why cyan and purple? They're not complementary
colors or anything...something to do with the properties of the sensor?
I know about chromatic aberration, which would seem to explain purple,
but I don't get cyan.

Ah, maybe cyan isn't quite the right way to describe. Here is a section
of the image magnifed 550x: http://lim.nl/Screenshot-dsc01421-550x.jpg

See what I mean? I am not quite sure what to call this color; maybe a
shade of aquamarine or something?

In any case, I am going to try the technique mentioned by Paul Heslop
above.

--
Colin Brace
Amsterdam

Colin Brace wrote:
See what I mean? I am not quite sure what to call this color; maybe a
shade of aquamarine or something?

No, I completely see what you're talking about - it's a kind of
blue-green - I just don't understand why that particular color would be
showing up in fringing. My curiosity is purely academic, anyway. :^)


--
Oh to have a lodge in some vast wilderness. Where rumors of oppression
and deceit, of unsuccessful and successful wars may never reach me
anymore.
-- William Cowper

Jeremiah DeWitt Weiner wrote:

Colin Brace wrote:
See what I mean? I am not quite sure what to call this color; maybe a
shade of aquamarine or something?

No, I completely see what you're talking about - it's a kind of
blue-green - I just don't understand why that particular color would be
showing up in fringing. My curiosity is purely academic, anyway. :^)

Where is that area located in relation to the center of the frame? If you
look equidistant in the other direction do you see the same fringing but
reversed? If you still have access to the location and similar lighting
conditions can you try the same shot with the camera inverted and see if
you get the same effect in the same place on the inverted frame?

You said it was a very hazy day--could that be simply a partial rainbow due
to the haze?

If it was being displayed on a CRT or 3 CCD projector I'd say that it looked
like a convergence problem--leads me to wonder if it could be simply an
artifact of the arrangement of pixels on the sensor.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)