ASA/DIN settings old and new cameras what happens inside?

[jan normandale]

I know what happens when I set the f-stop on a camera, I know what happens when I set the speed of the shutter on a camera. I don’t know what happens when I set the film's ASA/DIN on a camera.

Can anyone tell me what happens inside a camera when this setting is made? What about older cameras that didn’t have film speed settings. What is different between the newer cameras with that setting option and the old ones that don’t have a setting option.

Information, clarification (or links/URL’s) is appreciated.

Jan

 

[Wayne R. Scott]

Jan,

On the older cameras with no meter on camera, the ISO just reminds you of the film you have in camera. Newer cameras communicate with on board microchips to make the exposure decisions for you based on the ISO of film.

Wayne

 

[Gabriel M.A.]

Hi Jan. Hmm...well, it's not something that "happens" inside the camera. When you set your ISO/ASA/DIN speed, you're basically setting your camera's light meter. It's nothing but a scale. Light is measured in EVs (to simplify things).

EV 0 is essentially 1 sec @ f/1 with ISO 100. When your lightmeter receives more light (higher EV values) say, EV 10, then the same exposure at f/1 with ISO 100 would be 1/500 sec (I believe).

It's all Math. This may help you out: http://www.kenrockwell.com/tech/ev.htm

 

[rover]

Yup, just changes the sensitivity of the meter to match that of your chosen film, or that of your liking for your chosen film.

 

[jan normandale]

thanks ......

Jan