EV vs ISO on the D80

I took some photos in a darkened room during a meeting I attended. I thought

that instead of setting the ISO really high and getting grainy pictures I could

just increase the EV compensation. However the pictures were grainy anyway. So

what is the difference between EV and ISO in practice.

They are somewhat the same but different. The ISO setting defines (based on a recognised standard) how much exposure is required to render whatever you have metered as "mid toned". Sometimes you dont want that. For example when a great portion of your scene is snow or sand the meter tries to render that darker (make it mid toned) so you would dial in +1 or +2 stops of EV to over-ride the ISO setting metering. The opposite if you wanted to shoot a black cat in a coal mine.

 

On film cameras, you can effectively make EV variations by just changing the ISO setting as there is no linkage between the setting and the film's actual ISO. You want +2 stops of EV using 400 speed film, just set the ISO to 100 - done! You cant do it this way with digicams because changing the ISO directly affects the actual "film speed", in this case the sensor's responsiveness.

Ok. Makes a lot more sense now that it's been explained. Thank you very much.

By increasing the EV you've told the camera that you want a brighter image. Because of the other settings that you were using on the camera, it increased the ISO for you to get the brighter image. If you were using a flash, it may have increased the flash power instead to get the brighter image. Your camera's settings determine what it will change when you try in increase the EV.

I don't get it. If you increase the EV copensation in the camera, you simply get overexposed images. Increasing ISO yields correctly exposed images.

 

Probably, you mean you underexposed in camera and increased EV compensation in post processing RAW conversion. We discussed that before, and the agreement was, that it comes out the same as increasing ISO.