An image forming apparatus that provides consistent images on an elongated web-like recording medium. The image forming apparatus forms the image on the recording medium as it is supplied from a supply member and passes across an exposure station. An associated winding member is detachably installed in the apparatus to take up the recording medium supplied from the supply member. Placed on the winding member are indicia containing information on the exposure and developing characteristics of the recording medium. The operation of the image forming apparatus is controlled according to the characteristics information that is read by a reading device prior to the attachment of a leading edge of the recording medium to the winding member during the automatic feed of the recording medium.