Have you ever photographed a subject that is either very dark or very bright? Is it easy? Nope...it's not. There are several factors that make it difficult to photograph subjects that are mostly white or mostly black.
The camera's built-in algorithms nearly always get the exposure wrong when the subject is all white or all black. If ambient light is too low, the camera can't meter properly. When Jay was taking this photograph in Capital Reef National Park on a Moonless night, the camera could not accurately measure the exposure. He wanted to show the Milky Way as it is visible to the human eye. So, he used the histogram to determine the proper exposure without the help of the meter. He made a guess at setting that might work and took a single shot. Then he checked the histogram to see if the stars were bright enough - or too bright. He took several shots to determine the proper exposure.
Another challenge a scene like this poses is lighting the foreground object. There is enough light to capture the stars, but not enough light to capture the foreground. Jay used a headlamp to paint the foreground with just a small amount of light. Once again, he used the histogram to decide how much light was right for painting the foreground. He wanted to add just enough light to make the foreground visible, but not so much that foreground would appear to be obviously artificially lit.
High or low key subjects are often characterized by low contrast. Accurately focus is often difficult when you don't have high contrast edges to work with. This shot from Artist Paint Pots in Yellowstone National Park was a challenge for focus.
In order to get the shot he wanted, Jay set the focus to the correct distance using autofocus, and then switched to manual focus mode to lock the focus. Once the focus was locked, he could take several shots of exploding mud bubbles and hope to catch one with interesting patterns.
How much contrast is enough?
Once you overcome the challenges of exposure and focus, it's time to think about post-processing. Default software settings often pump up the contrast to bring out rich colors and details. With a low contrast image, increasing the contrast can actually make a photo less appealing. For this shot of Skógafoss in Iceland, Varina actually reduced the overall contrast slightly for a more nature look.
And then there's white balance. This can get a little tricky... especially with wide-angle photography. The scene we're working with here is actually relatively evenly lit, thanks to the full moon that painted the balanced rock with light. Beautiful. The problem is that the white balance for the sky is different than the white balance for the foreground. For this shot, Varina choose one white balance for the sky - making sure that the blue looked clean and natural. She chose a different white balance for the foreground, letting the color in the rocks take center stage. After processing the star-trails (that's a whole different issue), she used layers and masks to fix the color of the rocks.