Studio strobes are designed to give significantly more power and output than the hot shoe alternatives that mount directly to the camera. These units require a light stand, or a patient assistant to hold them. Some require AC power, others have a battery option, and a select few can do both. Manual controls are almost always available, with newer technology now also allowing TTL flash metering with a camera. Studio strobes can be very portable and used on location, with the main emphasis being power, control, and the ability to modify, or shape the light, to achieve an optimal creative vision.