Michael Wong wrote:
> I think everyone know the air quality is not good in Hong Kong :( Such as
> the following pictures, the hill at opposite side of the sea is not sharp &
> a haze cover the hill. A great difference from near side. How do I edit the
> picture to show the hill at opposite side same as near side in PS?
>
> http://palmboy.palmcyber.net/gallery/albums/album87/IMG2151.sized.jpg
>
How's this? http://www.moosemystic.net/Gallery/Others/MWong/Haze.htm
First, I agree with others that you might have been better off with a
filter in the first place. The reason I say 'might', rather than 'would'
is that you are at sea level, which is a different problem than high
altitude. At high altitude, bluish color and haziness is often caused
largely by excessive UV, to which the eye is not sensitive, but the
film/sensor is. The only good solution to that is a filter, and for
images to be post processed, a bit too much filter is better than too
little.
In this case, the blue cast is a result of scattering of blue light more
than the other parts of the visible light by the moisture in the air.
The same effect that makes the sky blue, but here putting "blue sky"
between you and the distant features. This also has the effect of
lowering contrast in distant objects, which makes detail less obvious.
To the extent that there is particulate matter, dust, diesel soot, etc.
in the air, there may be scattering of other colors of light, depending
on the amount and nature of the suspended matter and the angle of the
sun. This is the cause of sunset/sunrise colors. If there is enough, it
also simply blocks some of the light and also causes detail loss.
Also, there is s lot of movement in air at a local level, called cells,
within which air moves due to convection currents. In effect, there are
a whole bunch of parts of the air between the camera and the distant
subject that are moving in various different directions and contain
subtly different indexes of diffraction, so they all very slightly act
as lenses. Again, a cause of loss of contrast and sharpness. This effect
is worse where the air is warmer and where it is more humid. in a shot
like this, with lots of dark green foliage close in at the bottom, there
will be strong rising air currents right in front of the camera.
To the extent that these effects reduce resolution, there is no cure in
software. To the extent that the effect is due to reduced contrast,
software can do a pretty good job of recovery.
The use of a filter at sea level will reduce the amount of scattered
blue light and often enhance resolution/sharpness in distant objects.
The problem is that it will also change the color balance of near
objects. So people look for a filter that helps, but isn't too strong.
That's about all you can do with slides to be viewed directly. For
images that are going to be scanned, you may use a stronger filter, like
an 81A, or even 81B, and shoot a reference shot with a color reference
target in the frame. I use a WhiBal, but there are lots of different
ones around.
If this were an important shot and I were working with a tripod, I would
take duplicate shots with and without filter, I doubt that a Skylight 1B
would do much good. I'd go with one of the 81 series.
With a color reference, it's a snap to correct for the filtering the
nearer parts of the subject to look natural, then using less correction
for the distant parts. This requires a gradient layer or separate layers
for different parts of the image, but so does correcting without a filter.
As to what I did to you image, well.... I split it into three layers,
foreground, water and distant shore.
I did little to the foreground. The water had some LCE, Curves and
Levels applied. The distant mountain had lost of LCE, some Curves, some
81 photo filter applied, and a bit of color adjustment beyond that.
Doing color correction on a distant subject with haze and no color
neutral object to work from is tricky and more a matter of taste than
accuracy, especially for someone who wasn't there. So don't pay too much
attention to color.
Moose
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