What exactly is a Portrait? Most often it means a photo of a person from the shoulders up where the shoulders fill most of the frame, and the frame itself is longer than it is wide (eg. your camera is positioned vertically). So you are trying to capture a person’s upper body in such a way to provide detail and interest in the frame, without including too much detail about them. A cosplayer spends a lot of time on the upper body of the costume whether they realize it or not. That means it is a good area to focus on.
Two levels of interest (cosplayers from the same series).
With a nice portrait, you are capturing their face as well as the nicest area of their costume. One of the greatest benefits of portraiture from a photographer’s point of view is that there are a multitude of quality lenses out there specifically designed to take these types of images. Those being 50 – 85mm lenses with exceptionally large apertures that are great at producing nice blurry backgrounds. With a good angle, arrangement of the subject, and quality lens; portraits are the “money shot” of convention photography and easy to accomplish in almost any setting regardless of crowds, space constraints, or available light.
A standard portrait style image.
Let’s talk about your subject now. How should you position them, or rather in a time constrained setting, where should you stand to maximize the quality of your photo? You want to see as much of their costume as possible, yet don’t want to image to appear flat. That means their shoulders should be angled toward you, but not extremely so. Most portraits have the subject looking directly at the camera, but don’t shy away from experimenting with the direction of their face and eyes. Make the type of shot you want to make within the constrains of what can be considered a portrait pose.