11 Film exposure
SNAPSHOT
Beginners guide to understanding the three factors that affect exposure which are:
- Aperture
- Shutter
- Film speed (ISO)
What is exposure
Exposure is the amount of light that passes through the camera lens and reaches your film over a period of time (Light x time).
Exposure determines how light or dark your image is.
You control exposure by adjusting the amount of light you let into the camera. With too much light your picture will be too bright or overexposed, not enough light, your picture will be too dark, or underexposed.
Correct, over, and under-exposed negatives and prints
A correctly exposed negative will be easy to print resulting in an image with a long grayscale tonal range.
- Correct exposure results in a print and a negative that have details in the shadows and highlights of the image.
- Underexposure results in a print that is too dark and a negative that is too light.
- Overexposure results in a print that is too light and a negative that is too dark.
Below is an example showing the negatives and prints made from underexposed, overexposed, and correctly exposed negatives.
Obviously, the trick is to let just the right amount of light into your camera in order to get the correct exposure. The following three settings affect exposure. They are Aperture, Shutter, Speed, and ISO. Each one of these settings has a different effect on the overall image, however, their relationship to each other is critical to getting the correct exposure. Finding the right balance is all about understanding what each one does, how it affects the others, and how you can use it to be a creative photographer.
Some cameras offer a few easy options to get the correct exposure.
Manual Mode is camera mode that allows the most creativity.
Program or Auto Mode makes all the decisions for you.
Aperture or Shutter priority Modes are helpful settings but only after you understand how they each affect the image, and when to use them.
Different shooting modes
- Manual Mode The photographer chooses the aperture and the shutter speed to achieve the correct exposure (M).
- Aperture Priority Mode The photographer chooses the aperture and the camera chooses the shutter speed to achieve correct exposure (A or AV).
- Shutter speed Priority Mode The photographer chooses the shutter speed and the camera chooses the aperture to achieve the correct exposure (S or TV).
- Program Mode The camera makes the choices for the photographer automatically (P).
Manual Exposure is set by turning the shooting mode dial to M, while Manual Focus is set by setting the switch on the lens to M.
Let’s unpack this
Aperture controls how much light strikes the film (quantity).
Shutter Speed controls how long the light stays on the film (time).
Film speed ISO or (ASA on older cameras) refers to the film’s sensitivity to light.
Aperture
The aperture is an opening in the lens, not in the camera body itself. It functions a lot like the pupils in your eyes. When it’s dark, it open