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[OM] Re: [photo] Piazza del Popolo at dusk

Subject: [OM] Re: [photo] Piazza del Popolo at dusk
From: Moose <olymoose@xxxxxxxxx>
Date: Sun, 02 Dec 2007 16:51:48 -0800
You don't post many images, Fernando, but the ones you do are very 
special. Wonderful composition, light, etc.!

Fernando Gonzalez Gentile wrote:
> Yes, been there and found that.
>
> Perhaps I didn't try the most convenient option.
> Although I came out with very straight buildings, they showed me one 
> single problem: had to crop it badly.
>   
As AG suggested in the Zone-10 Forum on my article on perspective 
correction, one solution, if you have a wider lens, is to get the camera 
level and square to the subject. That will include extraneous stuff, 
which you crop out later. That gets everything nice and square from the 
start. OF course, it makes for a poor slide and makes the grain in the 
scanned image bigger. No free lunch!

It also avoids the problem of objects closer than the main subject 
having different perspective distortion. In this image, notice how the 
light pole in front of the left building/dome leans further than the 
building. There is no way short of major surgery to correct that in PS.

My recommendation is to partially correct the perspective. That requires 
less cropping and our eyes correct the rest. Another way to put it is to 
correct it out of the range of obvious to more subtle.

At least as significant to me as the perspective distortion are issues I 
presume were a result of using UnSharp Mask or a similar tool:

- The grain in the sky looks to strong and sort of unnaturally clumpy to 
my eye. This is a common effect from USM on grain in smooth, undetailed 
areas like sky. It acts on the grain edges, creating tiny halos.

- There are bright halos from sharpening all along the building/sky 
edges. And in many areas where the edge is highly detailed, the halos 
result in mottled, disturbed areas even out into the sky beyond the 
bright halo.

The solution to both of these is pretty simple. Select the sky area in a 
copy the base image layer, make it a mask layer and put it on top of any 
layers with sharpening. This leaves the original grain intact and will 
cover the sharpening halos and artifacts in the sky area.

Further adjustments to the sky may be beneficial, especially if it 
contains clouds, is too light, has too much obvious grain, etc. But it 
will still cover the artifacts from sharpening on the layers below.

In my version, I've partially corrected perspective, losing very little 
significant image content while making it much less obvious. It it 
weren't for the light pole, it would look even better.

I've also softened the grain in the sky while at the same time slightly 
enhancing the sharpness in the buildings. All done in one pass with 
NeatImage. PS is not the best at everything. Specialized tools for some 
things work better. I didn't try to eliminate the grain, just soften it, 
but it still has a slightly unnatural mottled look. JPEG compression may 
have also contributed to that mottling. The original grain would 
probably look better, less mottled, even if it benefited from a slight 
reduction.

I also corrected the building/sky edge artifacts in the central portion 
of the image. Hand work at 300-400%; tedious and less  pure than the 
solution above, so I only did part. But worth it, I hope, to illustrate 
how much more realistic it looks. That little white edge just screams 
"I've been Photoshopped! Look how brittle and edgy looking I am."

http://moosemystic.net/Gallery/Others/FGonzalezG/PdPopolo.htm

Moose

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