mr.wind-upbird Posted May 16, 2004 Share Posted May 16, 2004 Can anyone explain the relationship between Weston and ISO speed numbers? Many of my grandpa's old Kodachromes are marked "Weston 100" and other numbers. Link to comment Share on other sites More sharing options...
stephen_benskin Posted May 16, 2004 Share Posted May 16, 2004 I'm looking at a table that compares a number of different speed methods. This was published before 1960 so it is the old standard. <p> Weston 100 = ASA 125 <p> Weston 400 = ASA 500 <p> Looks like a third of a stop difference. Link to comment Share on other sites More sharing options...
lex_jenkins Posted May 17, 2004 Share Posted May 17, 2004 What Stephen said. Here are a few examples from my ancient Bewi Automat, which reads in ASA, DIN and WES (Weston). ASA: 80-125 DIN: 20-22 WES: 64-100 ASA and Weston scales retain their relative values upward and downward. DIN is a whole 'nuther thing. Link to comment Share on other sites More sharing options...
silent1 Posted May 17, 2004 Share Posted May 17, 2004 "DIN is a whole 'nuther thing." That's because DIN is an exponential (the same exponent base as decibels, in fact), instead of a linear scale. Any three degrees change in DIN is a factor of two -- so (IIRC) ASA 200 was DIN 24, while ASA 400 was DIN 27 (sorry, my keyboard hasn't got a degree symbol and I don't remember the ASCII code). That's convenient if you normally work in 1/3 stops, since the DIN scale is automatically in 1/3 stops, but it's one more step to think about when making exposure corrections (as, for instance, when shooting ISO 1000 film and using a meter that goes only to EI 400). Some would say it's easier, most likely people who knew DIN before ASA and DIN numbers were merged into ISO ratings. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now