To solve the following problem that when an image shot with a digital camera is projected on a big screen with a present optical overhead projector, since the aspect ratio of a screen of the digital camera is different from that of the big screen, if one of the length and breadth of the screen is used as a standard, the other causes excess or makes a blank space, therefore trimming is difficult.

This film strip sleeve is configured such that the dimensional ratio of a screen of a digital camera is used, a standard is set to A4 in screen printing, a film strip cut parallel to the minor side is defined, this is inserted into a projector, a screen pitch is set to 42 mm and a screen mask is made octagonal so as to attain adaptation to a larger length, a larger breadth and partial expansion of the full screen of the digital camera, cut to a single strip is made possible, and adaptation to a conventional slide is made possible.