Dyfyniad APA

Johnson, C. (2007). The practical zone system : for film and digital photography: A simple guide to photographic control (4th ed.). Elsevier/Focal Press.

Dyfyniad Arddull Chicago

Johnson, Chris. The Practical Zone System : For Film and Digital Photography: A Simple Guide to Photographic Control. 4th ed. Boston: Elsevier/Focal Press, 2007.

Dyfyniad MLA

Johnson, Chris. The Practical Zone System : For Film and Digital Photography: A Simple Guide to Photographic Control. 4th ed. Elsevier/Focal Press, 2007.

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