[rollei_list] Re: Rollei Flash
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Thu, 10 Jan 2008 11:17:28 -0800
----- Original Message -----
From: "ERoustom" <eroustom@xxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Thursday, January 10, 2008 6:02 AM
Subject: [rollei_list] Re: Rollei Flash
Thanks Richard. Do these guide numbers relate at all to
those given to electronic flashes?
Elias
The same thing, distance times f/stop. So, if a
particular film and bulb has a guid number of 200 it means
that for an object 10 feet from the bulb the f/stop is f/20.
Guide numbers vary inversly with the film speed, that is, if
you have the guide number for an ISO-100 film the GN for an
ISO-200 film will be twice the number. Because bulb flash
duration is long compared to the shutter time the GN also
varies with shutter speed, at least for faster speeds,
something which does not happen with strobe since the flash
duration is typically much shorter than the shutter speed.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
---
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
Other related posts:
