Contrast when Photographing in Direct Sun
Direct sun is light that comes right through the atmosphere to your subject. Mastering the art of macro photography using direct sun means controlling the relationship between shadows and highlights.
Too much contrast in a scene can lead to
Blocked-up shadows — underexposed areas that provide little to no detail
Blown-out highlights — overexposed areas that provide little to no detail
Your digital camera’s sensor is less sophisticated than your brain and can deal with a much smaller range of tonalities at one time. Because your digital sensor can’t compensate for scenes with such high contrast on its own, it’s up to you to bring the shadow and highlight areas closer together in order to capture detail in both at one time.
It's best if you expose for your highlights (making sure they don’t get blown out), and fill in your shadows with additional light to better expose them, as well. This technique enables you to create images that appear to your digital sensor closer to the way you see them with your eyes.
The image on the left shows how the camera deals with a lot of contrast. You see that it could not render information in the highlights and shadows. The image on the right shows the result of using a small reflector to bring up the luminosity of the shadows, allowing for a more natural-looking image.
You can use your battery-powered flash, ring light, and other macro-specific lights on low settings to fill in shadow areas as well.
100mm, 1/500, f/8, 200 100mm, 1/500, f/8, 200
To ensure both your highlights and shadows are exposed properly, refer to your camera’s histogram — a graph on your LCD monitor that shows the brightness distribution of an image with pure black on the left, pure white on the right and grey in the middle.
If you notice that a lot of tones are pressed all the way against the left edge of your histogram, then your shadows are underexposed. If a lot of tones are pressed against the right edge, your highlights are overexposed.