He's not kidding about the equipment they have to lug around besides their cameras. This is a segment on Quick Shot - a regularly scheduled US combat photographer (all services) refresher course on the "Combat" portion of their MOS (job description).
You take cover a lot, you hump the stuff over distances; the equipment's designed to take a beating, but something you can easily sweep to the side because you're going to have to return fire or do something else is preferable. 50 makes sense, a 35 probably even better; close up stuff. When you're not in the field, as evidenced by his other photos, you have the luxury of picking and choosing.