Digitally blending exposures

Here’s a little peek behind the lens on a recent morning spent at Otter Cliffs in Acadia National Park, and also a brief explanation of some of the things I do in post-processing to prepare images for display. I don’t usually get into this sort of thing here on the blog, but figured what the hey… someone might appreciate hearing the gory details.

One of the biggest challenges in landscape photography, especially at sunrise or sunset when there often is a wide range in the difference between lighter and darker areas in a scene, is that the camera can sometimes find it difficult to capture the full range of light. We’ve all made that picture where the sky was blue at the time, but appeared white and devoid of any texture in the photograph, or where the sky turns out great, but the rest of the picture is unnaturally darker than we wanted it to be. Our eyes are much more able to adapt to shadows and highlights than a camera is, though luckily there are a couple of solutions to this problem.

You can: 1) simply choose a combination of shutter speed, size of aperture, and iso that will give a more balanced, or average, single exposure, 2) use a graduated neutral density filter to hold back the light in brighter areas of the frame to get a “correct” exposure in one shot, or 3) you can bracket for multiple exposures and then blend them digitally when back home at the computer.

I find that averaging things out in a more contrasty early morning setting often doesn’t do the scene justice, and with my aging eyesight, I can’t be bothered fiddling with extra equipment such as filters in the field (especially if it is cold and dark). My method of choice when faced with a scene that exhibits high dynamic range is therefore 3) bracketing and digital blending using PS5.

f16, 1/2 second, iso 50

For this scene I bracketed several photographs one stop apart, each at the same aperture, though each with a different shutter speed. As you can see, the foreground rocks in the photograph above are decently exposed, but with a shutter speed of half a second, the sky is overexposed without detail and pretty much useless. Again, standing there in person I could see the wonderful colors in the sky AND the correctly exposed rocks, but the camera is not as capable as the human eye in dealing with this type of situation.

f16, 1/8 second, iso 50

In the second photograph, with a shorter shutter speed of one eighth of a second, the overall scene is a little darker with the foreground somewhat under-exposed, but in this frame the sky is a better representation of what I personally saw. Back at home in the warmth and sitting in front of the computer, I was able to apply a simple gradient mask between two separate aligned layers (steady tripod necessary), smoothly blending together and combining those parts of the scene from each image that I felt were better exposed. This achieves a similar result to using a graduated neutral density filter in the field, except that the GND doesn’t handle anything other than straight lines very well, so in my opinion (and specifically in this situation) digital blending offers more flexibility.

A simple combination of the two images from above

Some selective contrast and sharpening is then added, and voila… the finished product. My goal is usually to try and create a rendition of the scene that is somewhat similar to what I actually saw, though I have to admit as I work my way through this process I find myself taking creative license here and there and sometimes those pesky little saturation sliders get nudged more than they should!

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