Canon EF 180mm f/3.5L Macro USM EF180mm F3.5L MACRO USM Instruction Manual - Page 9

8. About Exposure Setting the Exposure When taking photographs using TTL metering, no exposure compensation is necessary to meter the light coming through the lens. With TTL metering, AE (autoexposure) is possible at all focusing distances. Just set the desired picture-taking mode, then check the shutter speed and aperture before taking the picture. Magnification and Effective f-number The aperture displayed by the camera assumes that the focus is set to infinity. The actual aperture (effective f-number) becomes darker (effective f-number increases) at closer focusing distances (magnification increases). This does not cause exposure problems for normal picturetaking. However, for closeup photography, you cannot ignore the change in the effective fnumber. When you use a handheld exposure meter to set the exposure, you must take into account the exposure factor shown in the following table. Magnification 1:10 1:5 1:3 1:2 1:1.5 1:1.2 1:1 Effective f/No. 3.8 4 4.3 4.7 5 5.4 5.8 Exposure in 1 3 stops - Factor (stops) in 1 2 stops - - + 2 3 + 2 3 +1 +1 1 3 +1 1 3 - + 1 2 + 1 2 +1 +1 +1 1 2 • The correct exposure for a close-up shot largely depends on the subject. Therefore, it is recommended to take several shots of the same subject at different exposures. • When taking close-up shots, it is recommended to use aperture-priority AE (Av) or Manual (M) picture-taking modes, because depth of field and exposure are easy to adjust in those modes. ENG-8