CASTLEFORD CAMERA CLUB THE EXPOSURE TRIANGLE

EXPOSURE, A DEFINITION In photography, exposure is the total amount of light allowed to fall on the photographic medium. In photographic jargon, an exposure generally refers to a single Shutter Cycle. “Correct exposure” may be defined as an exposure that achieves the effect the photographer intended.

THE EXPOSURE TRIANGLE

1. APERTURE Your camera works by taking light in through a lens and allowing it to hit a sensor in your camera which turns the light into a digital image. The aperture is a hole in your lens that opens and then closes again when the image is exposed correctly.

The aperture is made up of a number of interlocking diaphragm blades that open to allow the light into the camera. The size of the hole in the lens is measured by the f stop or f-number. The smaller the number (e.g. f2.8), the bigger the hole in the middle and therefore the more light is allowed into the camera.

2. SHUTTERSPEED This is the amount of time that we keep the shutter open. Along with the size of the hole (aperture) this also allows us to control how much light is allowed to hit the camera’s sensor. The longer the shutter speed the more light hits the sensor.

Shutter speeds are measured in fractions of seconds e. g Shutter speeds are measured in fractions of seconds e.g. 1/60 of a second or 1/2500 of a second.

3. ISO (International Organization for Standardization) ISO is the sensitivity of the cameras sensor to light. By adjusting ISO we can make the sensor more sensitive to light. The downside to having a high ISO is that as we lose clarity in our images. Increasing the ISO tends to mean the resulting photographs get more grain/noise.

Some cameras can cope with high ISO settings and The 3 images below were all taken with an Aperture at f5.6 and 1/250 shutter speed. By increasing the ISO the cameras image sensor becomes more sensitive to light, hence the images become brighter. Some cameras can cope with high ISO settings and handle noise really well. Image noise can also be corrected with numerous software packages and plugins such as Topaz DeNoise.

These two images were taken at very high ISO settings and you can clearly see how the noise on the image on the left has lost its clarity.

THE EXPOSURE TRIANGLE The Exposure Triangle is a fundamental principle of photography, developing an understanding of it will enable you to be more creative with your photography and create images with impact. If you would like to develop an understanding of Reciprocity, Highlights, Blacks, Exposure compensation, let the club know.

BRINGING IT ALL TOGETHER Aperture: Small f number = big hole in lens  = more light into the camera = Our photo appears brighter Shutter Speed: Slower shutter speed = more light into the camera = Our photo appears brighter ISO: Higher number = more sensitivity to light = Our photo appears brighter (but may be grainy)