Given that we have a sun room with ceiling-to-floor glass doors letting in lots of sunshine in all seasons, what factors would you consider in choosing between artificial lights and sunshine if you have that choice (i.e., daytime, cloudless sky)?
Below is my response comparing the advantages and disadvantages of using sunlight (or natural daylight) for product photography vs. using an artificial light source like fluorescent light or incandescent light. My response applies to product photography, especially for objects which can easily be accommodated indoors. Obviously, if you are shooting yachts, airplanes, or redwood trees my response would be different.
Sunlight does have a couple of advantages:
Sunlight is free and it is very bright.
On the down side:
The sun is constantly moving across the sky, so the orientation of your setup will need to change frequently.
The color of sunlight changes throughout the day. Sunlight is visibly more orange early or late in the day. But even over the course of a few hours in the middle of the day, the color of sunlight will change enough to potentially cause color related problems with your images. And if the sunlight light is bouncing off of anything like walls, bushes, tress, etc. it will also pick up a color cast which can be difficult to eliminate .
If you are not using something like a light tent as a diffuser, the sunlight will probably need to be softened. In addition, since it is a single directional light source, direct sunlight usually needs to be supplemented with reflectors. Reflectors can be difficult to support or position precisely. It's normally easier to rearrange a light fixture than it is to precisely control a reflector. And a fluorescent light fixture like one of our Kuhl Lites doesn't cost much more than a light stand with a reflector arm. So a lot of the cost savings of using the sun is lost, if you also need to buy holders for reflectors.
There is no sunlight available at night. With artificial lights you can shoot any time of the day or night any day of the year. Limiting your product photography to the middle part of sunny days will no doubt be somewhat constraining to the rest of your schedule.