iso setting

[okeefa]

sorry if this appears to be a really stupid question but what happens to the shot when the iso is changed?

i have a basic understanding of most of the camera functions from this site and YD and have messed around topside with my oly 5060wz but can't find anything on the iso.

again sorry for what must be a fundamental question.
cheers

keith

[TimIngmire]

Hi Keith,

OK ISO originally came from the days of film. Essentially you can buy films which are more or less sensitive to light - higher ISO equates to greater sensitivity and so suited for use in lower light / darker situations. However, higher ISO also equates to more noise.

Digicam also have a system where the sensor can be made to be more or less sensitive to light in exactly the same way. Like film, the higher your ISO the more noise you get in your picture although I think that you get less noise at high ISO's than you would from a comparable film shot.

So, the next question is why the hell you'd want to change the ISO. Well, in most cases it so you can keep the shutter speed as high as possible. Try it. Put your camera into aperture mode (so that the camera sets the shutter speed automatically) and take pictures in a room with increasing ISO setting. You will notice that with the higher ISO, the camera can select a faster shutter speed to keep the exposure the same. If you zoom to 100% then you should start to see an increasing amount of noise in the picture.

So, if you want to take a picture in a low light situation and need a higher shutter speed (eg if the shutter speed is so low that your will get camera shake or subject motion blur) then just up the ISO.

Some cameras can bracket on ISO which is a neat feature.

Have a look here: http://www.cameratown.com/guides/iso.cfm for some info and pictures.

HTH

Tim

[KenByrne]

ISO is a measure of the sensor speed. It used to relate to different films but now in a digital camera it means the amount of gain.

Your Oly is capable of ISO settings between 80 and 400.

Each doubling of the ISO doubles the speed of the sensor so it needs 1/2 as much light.

So a shot you take at 1/125 at F8 on ISO 80 need 1/250 at F8 on ISO 160 and 1/500 at F8 on ISO 320. or you can keep the speed constant and change the aperture so 1/125 at F8, F11 and F16.

The downside of increasing the ISO is an increase in noise in the picture. This is unwanted coloured spots , usually in dark ares of the picture.

My advice is always use the slowest ISO setting that allows you to get the shot. So on the Oly I'd be using 80 if I could and only going faster when it's a choice between getting the shot and a underexposed shot.

I've a Minolta compact that only has auto ISO and I find that it always seems to select low ISO settings so it maybe that using auto on the Oly is the easiest and best setting.

[okeefa]

thanks for the information, i'll be able to play with the satisfaction that i know what it does now. i think i'll stick to a low iso first and play with the aperture and shutter controls.