> I was going to ask how they controlled for the presence of compound bows & deer, trucks, and tank tops in the photos, but this implies they did not. Another o

> I was going to ask how they controlled for the presence of compound bows & deer, trucks, and tank tops in the photos, but this implies they did not. Another one would be lighting palette No need to read into implications. From TFA: "The procedure is presented in Fig. 1: To minimize the role of the background and non-facial features, images were tightly cropped around the face and resized to 224 × 224 pixels." While tightly cropping the face isn't perfect, it does address three of the four things you were specifically wondering about.