A person engaged in the business of sidewalk or street photography may employ additional operators not to exceed four in number on any one license who may, while engaged in such business, select and photograph persons as they approach the operator; provided, that such operator shall not engage the subject in conversation nor stop him longer than is necessary to hand out a card or coupon showing the address of the place where the picture may be obtained and the price for the same. No charge shall be made for observing any proof. Coupons not taken by persons whose pictures have been taken shall be recovered and not allowed to remain deposited on the streets. (Prior code § 26.01.045)