Fifty three years ago Mr. Van, my life drawing and painting teacher, told me to be very sparing with highlights when working with the human figure. That was while working with a spotlight in a classroom. In art school I made a study of light and it's effect on the human figure, driving Mr. Van nuts with my questions. I'm still studying the effects of light these days on the human figure and on everything I paint. I no longer use spotlights. I like natural lighting which I define as the light people live with, like a lamp in a living room or sunlight streaming in my studio window. Or the light that makes it through the canopy of the trees my models lay under. Seldom are highlights pure white. When the skin is wet, highlights appear white but even then they take on a bit of color.
I tell my students and any artist that will listen to work from life whenever possible. Working doesn't always mean actual painting or drawing. When having breakfast with my friends I study them for how the light is working on their faces and their hands as well. What the light coming through the window is doing to Georges face, his hands and what type of light is it. Is it a cloudy day a bright sunny day? Is there reflected light?
I recommend studying what the light is doing. Make notes, then take a photo and see the difference. In the studio I study Jordan's face for colors and the reason why those colors are there on that day. The colors change from day to day and it is mostly due to reflected light and what in the studio is causing those changes.
Using a photo off the internet you are not learning much of anything. You may even be hurting yourself. Nothing wrong with using photos as long as they are your own photos. Using a photo from the internet is nothing but copying someone else's work. When I take pictures to paint from I know the light falling on my subject, I know my subjects themselves. I have reasons for wanting to do a painting which makes me look at everything that will be going into it. How important are the hands, the feet, the folds in a skirt, the shadows on the blanket, the shadows on the grass around the blanket?
A hundred photos come into play along with years of experience working with the model I pick for a particular painting. I use the same models many times just so I know when I am looking at a photo to create a work of art, I know the circumstances effecting every thing in that photo. When sketching a stranger from a photo, there are reasons for wanting to do a sketch of that person. I make an effort to really study that stranger, to study his gestures. I never take these studies of strangers beyond studies. Sometimes I just need to sketch, I find sketching is quite relaxing.