Results 1 to 3 of 3

Thread: A question about film Exposure Index

  1. #1

    Default A question about film Exposure Index

    "A film rated at ISO400 with push processing up to EI 1600"

    Is that analogous to a digital sensor with a base ISO of 400 that we can select ISO up to 1600?

  2. #2

    Default Re: A question about film Exposure Index

    Quote Originally Posted by cks2k2 View Post
    "A film rated at ISO400 with push processing up to EI 1600"

    Is that analogous to a digital sensor with a base ISO of 400 that we can select ISO up to 1600?
    Well,yes and no.Conceptually yes but physically no.That is the physical process is different for both.Although film is made to work normally or be light sensitive at ISO400 and can expose it as if it was ISO1600 .It will mean technically underexposing for film meant for ISO400 and during film developing the time duration is lengthened/prolonged.It's like applying EV compensation to the film development process.

    For digital sensor,the light sensed is amplified to give effect of ISO1600 but because light signal is amplified the noise inherent in the circuit is also amplified so the noise artifacts is seen in the picture much like film in the physical sense as under microscope the film emulsion shows much bigger silver grains because of the chemical over development.Hope this makes sense.
    Last edited by one eye jack; 4th April 2012 at 08:44 PM.

  3. #3

    Default Re: A question about film Exposure Index

    Quote Originally Posted by one eye jack View Post
    Well,yes and no.Conceptually yes but physically no.That is the physical process is different for both.Although film is made to work normally or be light sensitive at ISO400 and can expose it as if it was ISO1600 .It will mean technically underexposing for film meant for ISO400 and during film developing the time duration is lengthened/prolonged.It's like applying EV compensation to the film development process.

    For digital sensor,the light sensed is amplified to give effect of ISO1600 but because light signal is amplified the noise inherent in the circuit is also amplified so the noise artifacts is seen in the picture much like film in the physical sense as under microscope the film emulsion shows much bigger silver grains because of the chemical over development.Hope this makes sense.
    actually, technically speaking, we are still underexposing the exposure and then pushing the signal digitally (through amplification), just that it all happens in the camera's electronics... so an argument could be made that it is the same as pushing film... except that for digital RAW files, we can do it again in post as well... so it's like we can choose to do it in camera or in post (although the results of doing it in post will probably not be as good as doing it in camera, all else being equal)... YMMV

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
  •