I use video taping to review some details that happened in the sparring and here is an example of how frame-by-frame review works its charm. Without video it's hard to tell if a blade alignment is correct or not in a bout:
The above example was taken from the sparring we had yesterday, which is joked as "RSW customers's massacre at Buddha's birthday" and some of the highlights can be seen here:
http://www.rsw.com.hk/activities.htm#buddha
The two we used in the photos were riot helmet while some of us do wear motorcycle helmet... Later we may have hockey helmet. Just got a piece of info about where to obtain that locally and may pay a visit to the shop soon.