Page 1 of 2 12 LastLast
Results 1 to 10 of 12

Thread: Does ISO convert to ASA with the new light meters?

  1. #1

    Join Date
    Dec 2012
    Location
    Born L.A.-NYC is 2nd Home-Rustbelt is Home Base
    Posts
    394

    Does ISO convert to ASA with the new light meters?

    My old light meter broke. I was going to buy a selinium Sekonic. It uses ISO. Does the ISO setting on the new meters = ASA setting for film? Or is the digital ISO different from ASA?

  2. #2

    Join Date
    Aug 2008
    Location
    Germany
    Posts
    1,381

    Re: Does ISO convert to ASA with the new light meters?

    The full ISO number (e.g. 100/21) combines the ASA and DIN ratings in their 1980's definition. Digital ISO ratings are defined differently, but they substitutable by definition, so that the difference between procedures only would have to interest you if you had to calibrate a camera from scratch without comparison to an already adjusted meter.

    ASA and DIN both were significantly reformed around 1960, with old meters and films up to a stop off in some conditions - but in general anything that old will be off by even more due to ageing, and requires recalibration.

  3. #3

    Join Date
    Feb 2006
    Posts
    3,114

    Re: Does ISO convert to ASA with the new light meters?

    Quote Originally Posted by Iluvmyviewcam View Post
    My old light meter broke. I was going to buy a selinium Sekonic. It uses ISO. Does the ISO setting on the new meters = ASA setting for film? Or is the digital ISO different from ASA?
    As far as lightmeters go, ISO and ASA are the same to all intents and purposes. Digital camera ISO may or may not be the same, depending on how the camera's manufacturer calibrates it.
    One man's Mede is another man's Persian.

  4. #4
    Abuser of God's Sunlight
    Join Date
    Aug 2004
    Location
    brooklyn, nyc
    Posts
    5,775

    Re: Does ISO convert to ASA with the new light meters?

    Quote Originally Posted by E. von Hoegh View Post
    As far as lightmeters go, ISO and ASA are the same to all intents and purposes. Digital camera ISO may or may not be the same, depending on how the camera's manufacturer calibrates it.
    Yes! Good point. The tests at DXOmark.com show the differences between nominal and measured ISO. It's usually within 1/3 stop or less, but you'd want to know if you ever use a dslr as a meter when shooting transparencies.

  5. #5

    Join Date
    Sep 1998
    Location
    GA
    Posts
    12,443

    Re: Does ISO convert to ASA with the new light meters?

    Quote Originally Posted by paulr View Post
    Yes! Good point. The tests at DXOmark.com show the differences between nominal and measured ISO. It's usually within 1/3 stop or less, but you'd want to know if you ever use a dslr as a meter when shooting transparencies.
    Since film speeds are just a suggested starting point the careful worker, analog or digital, should test their system - including the metering system - and tailor it to their preferences. It has always been so. Film speeds were always effected by lighting, exposure, filters, developers, developing time, etc. It was never an absolute.

  6. #6
    C. D. Keth's Avatar
    Join Date
    Apr 2006
    Location
    Salt Lake City, UT
    Posts
    1,843

    Re: Does ISO convert to ASA with the new light meters?

    Yeah, they mean essentially the same thing right along with EI. They come from different testing criteria but they're equivalent for our purposes and, as Bob writes, they're only a starting point for fine work anyway.
    CK

  7. #7

    Join Date
    Feb 2006
    Posts
    3,114

    Re: Does ISO convert to ASA with the new light meters?

    Quote Originally Posted by C. D. Keth View Post
    Yeah, they mean essentially the same thing right along with EI. They come from different testing criteria but they're equivalent for our purposes and, as Bob writes, they're only a starting point for fine work anyway.
    Nay nay. EI is whatever you choose to expose the film at, to suit your requirements, developing, printing, etcetera.
    I use Tri-X sheet film (ISO 320) at an EI of 200. ASA, ISO, DIN, GOST, and others are all traceable to certain standards.
    One man's Mede is another man's Persian.

  8. #8

    Join Date
    Sep 2001
    Location
    Dunedin,Otago,New Zealand
    Posts
    179

    Re: Does ISO convert to ASA with the new light meters?

    I have always understood ASA to be what is printed on the package,and ISO to be the rating which gives you the most pleasing results. I know they are not the same,and ISO was invented by some faceless committee in The Hague (?).
    I have rarely found them to be the same. The advice to "expose for the shadows - develop for the highlights has always been valuable.

  9. #9
    Abuser of God's Sunlight
    Join Date
    Aug 2004
    Location
    brooklyn, nyc
    Posts
    5,775

    Re: Does ISO convert to ASA with the new light meters?

    Quote Originally Posted by Bob Salomon - HP Marketing View Post
    Since film speeds are just a suggested starting point the careful worker, analog or digital, should test their system - including the metering system - and tailor it to their preferences. It has always been so. Film speeds were always effected by lighting, exposure, filters, developers, developing time, etc. It was never an absolute.
    True enough for film, but meters are expected to be calibrated to a fixed standard. If you decide you want to expose your ISO 100 film at ISO 64, you still need to set your meter to 64. With a dslr, this will often mean choosing a nominally lower setting.

  10. #10
    C. D. Keth's Avatar
    Join Date
    Apr 2006
    Location
    Salt Lake City, UT
    Posts
    1,843

    Re: Does ISO convert to ASA with the new light meters?

    Quote Originally Posted by E. von Hoegh View Post
    Nay nay. EI is whatever you choose to expose the film at, to suit your requirements, developing, printing, etcetera.
    I use Tri-X sheet film (ISO 320) at an EI of 200. ASA, ISO, DIN, GOST, and others are all traceable to certain standards.
    Yea, yea. If your definition is the truth, then why does Kodak recommend exposure indices for its motion picture film?
    CK

Similar Threads

  1. light meters
    By absolom in forum Cameras & Camera Accessories
    Replies: 15
    Last Post: 24-May-2012, 18:40
  2. Light Meters
    By Bill Kumpf in forum Cameras & Camera Accessories
    Replies: 47
    Last Post: 17-Jul-2009, 12:47
  3. Light meters sensitive to IR light!
    By bglick in forum Gear
    Replies: 26
    Last Post: 15-Nov-2005, 19:59

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •