Do ISO values for Film and DSLR cameras have 1 to 1 correspondence?

Question

For example, if we have a film with ISO/ASA speed of 100, is it equivalent to setting ISO = 100 on DSLRs?

Asked by Akram Mellice

Answer

Sort of... because ISO values for film don't even have a 1:1 correspondence. For example, Fujichrome Velvia 50 is rated at ISO 50, but if you set your camera on 50, you will generally underexpose. Most film photographers I knew set ISO 40 instead. However Kodak E-100 typically did expose properly at ISO 100.

A digital camera set at ISO 100 will typically respond "as if" it were film that responded with a proper exposure at ISO 100.

Film photographers grew to understand the characteristics of the particular film they were using and adjusted accordingly. Digital photographers don't typically have that problem.

Answered by Steve Ross

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