Gerhard Kapitzke on Nosebands

Left: A simple bridle without a noseband is the most pleasant, force-free scenario because it allows the horse unlimited chewing activity and does not restrict him in any way.

#2: An English noseband (sometimes called a "cavesson") is the mildest noseband you can use--if buckled fairly loosely. The jawband runs directly under the cheekbone around the horse's head, resting on solid, less pressure-sensitive bone. When the reins are tightened, the pressure is dispersed onto the nasal bone and the lower jaw, and it is further lessened by a wide strap. The noseband prevents the opening of the horse's mouth, but still permits sufficient chewing activity. Because of its high position on the head, it does not impede the horse's breathing.

#3 A dropped noseband can be the most troublesome for horses because it is so often used without an understanding of its purposes and with intended force. When used by hard hands, pressure points are focused on the chin groove and the lower, sensitive area of the nasal bone. If adjusted too high, this noseband pulls the bit into the corners of the horse's mouth. If adjusted low, it restricts the horse's breathing. There should be room for two or three fingers between the noseband and bone in order to make such restriction bearable for the horse.

Inappropriate Nosebands:

#4: A figure eight noseband has crossed straps that can slip if the rosette in the middle has not been stitched tightly. The often thin, rounded straps may cut into the horse's skin.

#5 A lever noseband. Both of these noseband styles extensively restrict the chewing activity because of the straps surrounding the lower jaw, although breathing is not inhibited.

The English noseband remains preferable because it only encompasses the lower jaw once and does not restrict chewing activity.

For more on Gerhard Kapitzek's book, you will find it here: The Bit And The Reins.