Something occurred to me, this past weekend, that should've clicked a few years ago. Due to work commitments on weekends, I wasn't doing much photography from last Thanksgiving through the end of February. Also, northern Arizona is in the midst of a historic winter season. We've had about 160 inches (4 meters) of snowfall, which ranks 5th all-time in Flagstaff annals going back to the 1890s. The places I normally go to do wildlife and bird photography have been unreachable until recent weeks.
With my weekend schedule easing since early March, I've been able to get back into the groove. Something I've noticed and thought a bit odd is that the settings I normally use in the field haven't been meeting my needs. On a clear sky day, I normally use f/5.6, 1/2000, ISO 400 to photograph birds in-flight. During my recent outings, I've been using f/8, 1/2000, ISO 400 or f/5.6, 1/3200, ISO 400. In other words, I've had to decrease exposure by 2/3-stop in order to produce the image lightness I like.
I know, I could've used a lower ISO. However, I like being at ISO 400 with the D500 because that's in the camera's invariant range.
This isn't a bad thing. Though, I had entertained the notion that my camera wasn't working normally. This weekend, however, I had a moment of clarity and figured it out.
While standing atop a rocky ledge overlooking Mormon Lake with my back to the wind, I turned to look over my should to see when passing overhead clouds would clear and it came to me. Roughly 3 square miles of the lakebed is covered by a foot of snow. There was open water in some places but most of the lake is frozen and covered by snowfall. This made Mormon Lake a giant reflector and the reflected sunlight was adding 2/3-stop illumination to my subjects. The giveaway was the brightness of the undersides of the hawks, eagles, turkey vultures, and ravens. Even with the Sun at a relatively high angle, all the undersides were well-illuminated...by sunlight reflecting off the snow-covered lakebed.
So, here's a tip for all you new wildlife and bird photography enthusiasts. If you live in a place that gets snow during winter, be mindful that the exposure and ISO settings that work for you during the summer may not work as well during the winter months. If there's snow about, sunlight will reflect off the snow and onto your subject. The Sun will be acting as both a key and fill light. This isn't a bad thing but it does have the potential to be a bit confusing if the settings that worked well for you in sunny conditions are suddenly putting too much light on the sensor in mid-winter.
Also, with the Sun working as both a key and fill light, the elevation of the Sun above the horizon is largely negated as an issue. During the summer and autumn months, the undersides of birds can be completely in shadow when the Sun is at too high an elevation. However, during winter with snow on the ground, the reflected fill light illuminates birds from beneath even when the Sun is 50+ degrees above the horizon. This is a huge advantage of winter bird photography.
A red-tailed hawk glide along the rim overlooking Mormon Lake in northern Arizona (Nikon D500 w/ Nikkor 200-500mm f/5.6E at 500mm, f/5.6, 1/3200, ISO 400)
