Shutter speed, aperture, and ISO are the three most fundamental parameters in photography, and with them, you have control over both the technical and creative aspects of your exposure. Together, these three parameters form the exposure triangle. Learning the triangle should be a priority for any new photographer, and this excellent video tutorial will show you everything you need to know to master it and take full control of your images.
Coming to you from John Gress, this awesome video tutorial will show you the ins and outs of the exposure triangle. The concept of the exposure triangle was made to encapsulate the fact that shutter speed, aperture, and ISO are not independent parameters; when you vary one, you must vary one or a combination of the other two to restore the original balance in the exposure. This means that making a successful image is an act of balancing your creative vision for the shot with the needed settings for a technically correct exposure, which is why it is so important to become comfortable with it as soon as possible in your photography journey, as it will give you the kind of creative you are looking for. Check out the video above for the full rundown from Gress.
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If we are going to be discussing the so-called "exposure triangle", then we should make it clear that the term is a misnomer.
Exposure means how much light the image-recording medium is exposed to.
The amount of time the shutter is open effects how much light the medium is exposed to.
The aperture of the lens effects how much light the medium is exposed to.
ISO does not affect how much light the medium is exposed to ... it merely determines how sensitive the medium is to the light.
Hence, from a technical and semantic standpoint, ISO does not have anything to do with the exposure itself. So there is not actually an exposure triangle, as there are only two factors that technically have an impact on the exposure.
Just because a term has been in widespread usage for decades and decades does not mean that it is correct.
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