well, certainly the evening should be quite productive as well. Choice of whether to shoot morning or evening is based on location and the direction you need to shoot, sunrise on the U.S. east coast usually much more productive than sunset, but just the opposite on the west coast. The time of day isn’t just about the quality of the light, but the direction of light and how that affects shading, texture and dimension of the desired subject matter.
As far as being productive in the middle of the day, while I might not be actively shooting, that’s when I’m actively finding that locations I want to shoot, and evaluate the best time of day to capture it when the light will be best.
I’ve never worried that I need to actively shoot all the time, but I will say I have more evening shots that morning shots in my portfolio, mostly because the subjects in my location lend themselves to evening light better, as well as sunsets tend to be more colorful as the heat of the day brings in clouds and even thunderstorms, whereas the morning the skies tend to be bald. Not that that’s bad, I have many nice shots with a beautiful clean blue sky, but generally some clouds add nice interest and can help the light.
