Monday, February 7, 2011

Deep Blue Skies

Through correct exposure and simple postprocessing, it can be relatively easy to get deep blue skies even without a circular polarizer.

Overview: the key is make sure clouds aren't blown out when you capture the image.  In general, this will require a high shutter speed, a narrower aperture, and/or a lower ISO.  The exposure that will be dark enough to capture clouds will likely make the subject very dark.  We correct for this using flash to illuminate the subject.  After the image is captured, you can then adjust the blue channel's luminance to change the sky into a deeper blue.

For the shot above, here's what I did:
1. When I was choosing my exposure, I made sure clouds wouldn't be blown out.  I confirmed this by confirm this by looking at the LCD preview screen to watch out for blinking highlights.  As long as the clouds are not blinking, I knew I would later have the flexibility to change the color of the sky. I also knew I would be adding flash, therefore I immediately switched to my sync speed (1/500 in the case of the Nikon D70).

2. I added flash to illuminate the subject.  Rather than overpower the natural light (in this case, the sunlight, shining upon the subject's right shoulder), I wanted to respect it.  Flash was merely acting as fill light and I made sure to dial down the Flash Exposure Compensation to make the flash intensity look more natural.  I also used a handheld umbrella (with a Propet umbrella bracket) to soften the light - mimicking the softness of shade on the subject.

Here's how the shot looked, straight out of the camera.

3. In Lightroom, after I did the usual tonal adjustments, I went to the HSL menu in the Develop module and selected Luminance.  I clicked on the Targeted Adjustment tool (the one that looks like a little bullseye).  I clicked on any part of the blue sky, then dragged down the cursor.  The Targeted Adjustment selected the correct proportion of color channels (Blue and Aqua in this case) to change the color of the sky.  What I find cool is that because it affects the entire image, even reflections are adjusted (check out the water below).

In other postprocessing apps, I think you can get the same effect by adjusting color channels, though you may have to do some trial and error.

4.  I chose "Edit in... Photoshop Elements" and used content-aware spot-healing to get rid of the junk in the background.

5. Back in Lightroom, I added a slight vignette to complete the image.

Note: the first step here - getting the right exposure is essential.  In this shot, some parts of the clouds were blown out:

When I adjusted the skies, the result didn't look as convincing:

Anyway, here's another example of this technique.  This one was interesting to me, because I was able to edit it in literally just two or three minutes, using the content-aware spot-healing tool of Photoshop Elements 9.

For comparison, the original shot looked like this: