Cinematography: Exposure Experiments

In our second Cinematography class we joined the Photography class to learn more about the exposure triangle, and define a few terms.

The Exposure Triangle. (2013). Retrieved from http://djshawphotography.com/new-dslr-the-exposure-triangle/

The Exposure triangle is made up of the Iso, Aperture and shutter speed; which are the key elements that need to be correctly balanced to achieve correct exposure in a photo or film.

Aperture: Measured in F-Stops, this refers to the lens or eye of the camera which can be opened of closed in order to let in light.  The F-Stop is a ratio between the diameter and the length of the lens.  An F-Stop of 22 is has a smaller diameter opening and lets in less light than an F-Stop of 1.4, and each stop either doubles or halves the amount of light let into the camera.

Shutter Speed:  The shutter speed is measured in time, and refers to how long the shutter is open.  Shutter Speeds are given in fractions of a second.

ISO: ISO is the sensitivity of the camera's sensor.  If a camera is being being used in low light then the ISO may need to be increased.

Each of these elements are affected by light, which is the main factor influencing any changes to these settings.  In order to correctly exposure a photo these elements need to be balanced.  The most commonly noted connection is the relationship between Aperture and Shutter Speed.  If a low F-stop (eg 1.4) is used, more light will be entering the lens. To counterbalance this a faster shutter speed must be used to limit the amount of light and prevent overexposure. 

Low F-Stop (1.4) = Short Shutter Speed
High F-Stop (22) = Long Shutter Speed

These are all things I learnt during photography classes taken at school, so they are all familiar concepts.  However in regards to film, this is something that will take a little bit to wrap my head around, as it is obvious to me how these things affect a stills camera but not so clear how this translates.

To illustrate these ideas further we completed an exercise where we needed to take a number of correctly exposed shots using as many different Apertures as we could.  For this exercise the Shutter Speed and ISO were locked, although we did alter the shutter speed once during the exercise to allow for the weather conditions.  This ended up being a really useful way to show the theory in practice.