Paper × 841 mm). A1 is half the size of a sheet of A0 (i.e., 594 mm × 841 mm), such that two sheets of A1 placed side by side are equal to one sheet of A0. A2 is half the size of a sheet of A1, and so forth. Common sizes used in the office and the home are A4 and A3 (A3 is the size of two A4 sheets). The density of paper ranges from for tissue paper to for some speciality paper. Printing paper is about . Paper may be classified into seven categories: Some paper types include:
Paper texture effects in calotype photography make them more transparent. Since many prints could be made from a single negative, travel photography became possible, and prints from calotypes were soon distributed in book form and sold in shops. The chemical operations used to make a calotype were not difficult to perform, and relatively few specialized supplies were required. But the process had a serious deficiency, and it was quickly replaced by photography on glass when this became practical. Paper texture limits what can be done with the calotype process. This texture can be seen by holding a piece of copier paper up to the light: the