>>3529706>Aperture (how much light lens lets in)-wider aperture(usually <f4)=shallow DOF (Blurry background), narrower aperture (usually >f4)=sharper image
>Shutter speed (how fast shutters open/close)-faster shutter speed means more able to capture faster moving objects and also decrease camera shake from hands (less motion blur), but also means less light let in
-rule for at least compensating for camera shake is use at least 1/(focal length) for full frame, e.g. 1/50 for 50mm, for crop you need to apply crop factor to the lens and apply that equivalent so 50mm on crop acts like 75mm (50mm*1.5=75mm), so use at least 1/75 on crop.
>ISO (how sensitive the sensor/film is to light)-higher sensitivity = more sensitive to light, but also more likely to show grain
-this is probably the most frustrating because theres not really a rule, so what i did is look at how they used to do it with 35mm film, where the ISO is based on the film they use, so they were stuck with one ISO until they changed the film. But basically the most common ISOs were 100,200,400,800, where 100/200 were used for sunny environments, 800 for low light/night, and 400 for inbetween. I use those as standards, and change if i need to. With newer cameras these days, they can get away with higher ISOs while still maintaining minimal noise.
>Some aids to help figure it out-Sunny 16 rule, where on a sunny day generally you can use f16, can use any ISO, and shutter speed is 1/ISO
-Light metre, either in your camera, can buy a seperate light metre device, or even get an app, which will tell you if you're overexposed/underexposed, so you can change your exposure triangle until you get it right
Other than that its basically trial and error