camera (36X24mm), an object with the size 18x12mm would take 1/4 area of your photo. For example, the 12 megapixel Micro Four Thirds Panasonic Lumix DMC-GH1 camera with a 2x crop sensor only requires a 1:2 reproduction ratio to take a picture with the same subject size, resolution, and apparent magnification as a 12 megapixel "full-frame" Nikon D700 camera, when the images are viewed on screen or printed at the same size. Thus a Four Thirds system macro lens like the Laowa 50mm f/2.8 2X Ultra Macro Lens with a maximum image magnification of 2.0x is rated as having a "4.0x 35 mm equivalent magnification". To calculate 35 mm equivalent reproduction ratio, simply multiply the actual maximum magnification of the lens by the 35 mm conversion factor, or "crop factor" of the camera. If the actual magnification and/or crop factor are unknown (such as is the case with many compact or point-and-shoot digital cameras), simply take a photograph of a mm ruler placed vertically in the frame focused at the maximum magnification distance of the lens and measure the height of the frame. Since the object height of a 1.0x magnified 35 mm film image is 24 mm, calculate 35 mm equivalent reproduction ratio and true reproduction ratio by using the following: (35 mm equivalent reproduction ratio) = 24 / (measured height in mm) (True reproduction ratio) = (35 mm equivalent reproduction ratio) / Crop factor. Since digital compact camera sensor sizes come in a wide diversity of sizes and camera manufacturers rarely publish the macro reproduction ratios for these cameras, a good rule of thumb is that whenever a 24 mm vertical object just fits, or is too tall to fit in the camera viewfinder, you are taking a macro photograph. Technical considerations Depth of field Limited depth of field is an important consideration in macro photography. Depth of field is extremely small when focusing on close objects. A small aperture (high f-number) is often required to produce acceptable sharpness across a three-dimensional subject. This requires either a slow shutter speed, brilliant lighting, or a high ISO. Auxiliary lighting (such as from a flash unit), preferably a ring flash is often used (see Lighting section). Like conventional lenses, macro lenses need light, and ideally would provide similar # to conventional lenses to provide similar exposure times. Macro lenses also have similar focal lengths, so the entrance pupil diameter is