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01/12/2007 12:33:36 PM · #1 |
What tips do you experienced photographers have for avoiding artifacts in intensely blue skies?
Do you have tips for the initial in camera exposure?
I notice that even with well exposed photographs of buildings against blue skies, with and without a polarizer, the blues tend to have minor and sometimes major artifacts. Using a polarizer to intensify the blue skies seems to intensify the artifacts too, unfortunately.
Do you have any tips for Photoshop processing to hep remove artifacts?
Using noise reduction software (Noise Ninja in my case) on various custom settings as either a selection or on the image as a whole does not seem to be entirely effective. Gaussian blur helps a little but not always. Any other tricks of the trade? Avoiding increasing the contrast and over sharpening (which does not really need sharpening after all) helps avoid accentuating what might already be there in the way of artifacts. The blues seem to have a tendency to "clump" up and produce artifacts with even mild processing.
As an example, the image below is a 100% crop from a cityscape. The blues especially in the sky at the left side show artifacts. Even using Gaussian blur it is hard to get rid of them.
Regarding workflow: I shoot in RAW, convert to TIF 16 bit and do as much of the processing as possible in 16 bit TIF. Photoshop 6.0 which I use (antediluvian, I know...) allows some - but not all processing in 16 bit. Generally speaking, I make very minor adjustments in RAW before sending to TIF.
Is the 30D or 5D Canon less susceptible to this issue? By the way, I have no in-camera or transfer settings on auto so no sharpening or whatever is done in camera or in the transfer process.
Voting on the Best of 2006 challenge, I notice that there are quite a few landscapes in which the blue skies (both light and dark azure) suffer from intense artifacts. Therefore, I think this subject might be of interest to a number of people.
Thanks for your suggestions... in advance.
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01/12/2007 12:40:48 PM · #2 |
| Looks like noise to me, and the blue channel tends to be where a lot of noise shows up. |
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01/12/2007 12:43:09 PM · #3 |
Originally posted by routerguy666:
Looks like noise to me, and the blue channel tends to be where a lot of noise shows up. |
I concur.
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01/12/2007 12:55:12 PM · #4 |
Wherever there is underexposure, there is noise. Blue skies are more or less by definition "underexposed", in the sense that if they are dark at all they are Zone 4 or below. So they WILL show noise, and the more you polarize 'em the more you will get. The more contrast you add, the more you will get. And so forth and so on.
You can compensate to a certain extent by cloning off a BG copy, selecting for the blues, and applying gaussian blur. Then clone off THAT copy and throw a smidgeon of high pass sharpening into the mix, and set the layer to "overlay" mode and merge it down into the blur layer. Like so:
R.
Here's the modified version overlaid with half the original version, for easy comparison:
Message edited by author 2007-01-12 13:00:46.
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01/12/2007 12:59:30 PM · #5 |
Robert - Thanks. I think I understand now.
Someone tell me the difference between artifacts and noise, please. |
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01/12/2007 01:02:01 PM · #6 |
Originally posted by pineapple:
Robert - Thanks. I think I understand now.
Someone tell me the difference between artifacts and noise, please. |
Artifacts are produced by the processing; noise is present in the original data. Noise may be accentuated by PP to the point where it appears to be artifacts, but it was always there.
R.
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01/12/2007 01:06:45 PM · #7 |
Another technique I haver sometimes used successfully is to select the sky, use the eyedropper to select a color from the darker range of the sky for foreground and from the lighter range for, create a new layer with mode multiply, load the sky selection on it, and paint a foreground-to-background gradient on it. This will darken every part of the sky that is lighter than the color overlaying it, and sometimes smooths things out a lot. But it's difficult to use if there's much variation in the sky.
R.
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01/12/2007 01:13:23 PM · #8 |
| Aha, that sounds like a good idea in this case where there are no clouds or uneven variation in the blue gradient from top to bottom. |
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01/16/2007 12:02:23 PM · #9 |
| sometimes i high iso setting can leave noise what was urs??? |
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