Carlos, in other words, yes? That is, not the existing light, but the flash's light reflected back off the subject determines the duration of the flash? Robert
The automatic flash units with sensor have a computer that calculates the flash duration according the sensor info, the sensor captures the subject reflected light, less light from the subject more flash duration, more light reflected from the subject shorter flash duration. The simplest flash units with sensor works automatic for one distances range only, f.e. the referred Rollei 20 works automatic from 0.4m to 4m only and within this distance the flash computer calculates the flash duration according the light from the subject selecting between 1/2500 sec to 1/30000 for the flash duration; a complex flash like the Vivitar 283 works automatic for four distances range: 0.6m to 3.4m; 0.6m to 4.5m; 1.2m a 9 m and 1.5m to 13-1m, each automatic distance range requires to adjust a different f stop in the camera. The Vivitar 283 has 1/1000 sec flash duration for the manual mode, and 1/1000 to 1/30000 sec for the automatic modes. The guide number for the manual mode using ISO 400 film is 72, and then (f.e.) if the subject is 20 metres from the camera you need to adjust the camera f stop at f 3.5 (72/20= 3.6). All the best Carlos --- Robert Meier <robertmeier@xxxxxxxxx> escribió:
>The flash >duration for the automatic mode can vary from 1/2500 >sec to 1/30000 sec according to the existing light. Carlos -- Did you mean, according to the distance to the subject (and thus the light reflected back from the subject)? --- Rollei List - Post to rollei_list@xxxxxxxxxxxxx - Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe' in the subject field OR by logging into www.freelists.org - Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with 'unsubscribe' in the subject field OR by logging into www.freelists.org - Online, searchable archives are available at //www.freelists.org/archives/rollei_list
__________________________________________________ Preguntá. Respondé. Descubrí. Todo lo que querías saber, y lo que ni imaginabas, está en Yahoo! Respuestas (Beta). ¡Probalo ya! http://www.yahoo.com.ar/respuestas --- Rollei List - Post to rollei_list@xxxxxxxxxxxxx - Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe' in the subject field OR by logging into www.freelists.org - Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with 'unsubscribe' in the subject field OR by logging into www.freelists.org - Online, searchable archives are available at //www.freelists.org/archives/rollei_list --- Rollei List - Post to rollei_list@xxxxxxxxxxxxx- Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe' in the subject field OR by logging into www.freelists.org
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