ISO – This setting changes the sensitivity of the camera.
The lower the ISO the least sensitive the camera is to light and the higher the ISO the most sensitive the camera is to light. So the higher the ISO the most most sensitive the camera is to light and the less amount of light is needed.
ISO settings of 100-400 are for outdoor sunlight use.
ISO 800 is for low level sunlight.
ISO settings of 1000 and above are for low light and evening light.
Aperture – This setting changes how wide the aperture of the lens is.
The lower the setting, the more amount of light is let into the lens and the lower the depth of field.
The higher the setting, the less amount of light is let into the lens and the higher the depth of field.
F1.8 is used for darker conditions but also creates a narrow field of focus.
F5.6 and above are used for lighter conditions and create a wider field of focus.
Above is an image which shows the difference between how a high apeture and a low apeture is creating a different depth of field. It is showing showing a larger aperture is creating a more deep depth of field where as a lower apeture is creating a more shallow depth of field.
Shutter Speed – The speed in which the camera shutter opens and closes.
The faster the shutter speed the more focused the picture as the exposure of light is smaller and more precise..
The longer the shutter speed the least focused the picture is as the exposure of light is larger.
To create a narrow field of focus in the day light conditions, you would need to use a medium ISO setting and a low Aperture setting.
To create a wide field of focus in the day light conditions, you would need to use a higher ISO setting and a higher aperture setting.
This an example of photograph which has had a ISO setting of 200 and a low aperture setting of f/2 which is creating that shallow depth of field.