Who can explaine ISO
Posted:
Wed May 14, 2008 1:24 pmby rmouads
My question is what is ISO i want know details
Re: Who can explaine ISO
Posted:
Wed May 14, 2008 3:54 pmby dang
I'll give it a shot.
ISO is a term originally "coined" for the light gathering speed of film. The face of transparent celluloid is coated by silver particles, which are light sensitive.
It's also referred to as ASA (ASA: A number set by the American Standards Assoc. ISO: International Standards Organization)
To easily explain how ISO is figured, the smaller the silver particle, the less chance it has of being exposed to light. If you'll visualize dimes & silver dollars... Lay the two coins on the ground, spray a mist of water above them, and which coin size will more water land on? Obviously the silver dollar, so it's given a higher ISO.
When related to film:
Particles that are exposed to light remain after processing, and those not removed. This gives the density which varies tones from black, to clear. The film is, of course, the negative whice requires more processing/enlarging to make "prints.
Higher ISO came at a price though, that being "grain" (later digitally termed "noise" due to dot size of sensors).
To explain this:
If you arrange coins of the same size laying flat on a piece of paper, the larger the coin the more space you'll have between the corners. Once you enlarge the negatives, the larger particle dots are more pronounced, and so is the space between them, giving you the visual grain.
Hope this makes sense.