Sun pictures are not always simple circles. Back in 2017, my youngest daughter and I went on a backpacking trip that started during an eclipse. The above photo shows the ground shadows in the parking lot near the start of the eclipse. If one wasn’t paying attention, one might not realize how weird they look.
In terms of preparation, I brought a small screen in the form of paper taped onto a box and an aperture, in the form of a cardboard sheet with a center region of aluminum foil with a small hole.
The above sequence shows the progression of the moon across the sun as imaged on my paper screen. For those pictures, I used the small hole in the foil as the aperture, but we could also see good sun pictures using our hands:
Even the shadows would start to resemble the shape of the eclipsed sun.
Also, notice how the sun pictures from foliage change during the eclipse.
At the start, the crescent sun points up and left (left photo, ~9:45 am), while nearing the end, the crescent sun points down (right photo, ~10:25 am). The next opportunity for a nearly total eclipse in the US is in 2044, a long time away. But if you pay attention, you might find other opportunities for interesting sun pictures well before then. Just remember that the moon is not the only thing that can eclipse the sun. Nor is the sun always without distinctive markings. In the early 2000s and with unaided eyes, I was able to see a very large sunspot on the rising sun when it was behind some serious low-level haze. It may have also been visible in sun pictures later in the day, though I did not think to look at the time.
Curiously, throughout the whole eclipse, the surroundings seemed about as bright as before. I noticed only a slight dimming of the landscape, like that when a very thin cirrus passes in front of the sun, which was curious given that about 80-90% of the sun was blocked out. Perhaps this is a result of the remarkable range of light intensities perceivable by our eyes. Having an independent measure of light intensity would be revealing.
–Jon