ISO-This setting changes the sensitivity of the film.
When low, the less sensitive the film is and the more light you will need. Therefore the higher the setting, the more sensitive the film is and the less light you will need.
For example ISO settings of 100-400 are for the outdoor sunlight use and reaching 800 is for low level sunlight. Additionally ISO settings of 1000 and above are for light and would suit night time more. Finally extremely high levels will make a graining effect and present the shot as fuzzy.
Aperture-This setting changes how wide the lens is also being the depth and field of the frame.
Higher apertures allow very small amounts of light to go through and reach the image sensor e.g. high aperture F5.6. Whereas a small apertures filters high amounts of light through e.g. small aperture F1.8. This means it has a shallow depth and can create a narrower field of focus on the foreground or background. This can be utilised to direct audiences focus on something easily, from blurring everything else out. Therefore higher apertures have a deep depth and can show everything in the frame in focus, having a wide field of focus.
Shutter Speed- This is the normal amount of time for a shutter to be open and allow a certain amount of light in. It effects the amount of light that reach the image sensor.
Fast shutter– can be used to capture an image.
Slow shutter- can be used to capture an image which looks like its moving.
The shutter speed makes the ISO and aperture compensate for its light intake. Therefore the speed of the shutter makes the aperture and ISO change to make the image clear or focus or blurred etc.