Ansel Adams / Temps de pose

"The choice of shutter speed must be made with consideration for (...) the loss of image sharpness caused by slight camera movements during exposure. The general rule to observe whenever the camera is handheld is to use as fast a shutter speed as you can, consistent with the requirements of exposure and depth of field. Tests I conducted some years ago (...) indicated that, using a normal lens (...) the slowest shutter speed that ensured maximum sharpness was 1/250 second. (...) even with firm body support image sharpness was noticeably degraded at 1/125 second (...)"

Ansel Adams recommende en conséquence de ne pas appliquer la règle habituelle des 1/F (1/100 pour un 100 mm, 1/60 pour un 50 mm, etc) mais d'ajouter deux unités (donc 1/500 pour le 100mm, 1/250 pour le 50mm).

Source: Ansel Adams / The camera - the Ansel Adams photography series I / Little Brown and Company / douzième édition brochée / 2005 / p 116