Capturing light..

"What matters in photography is not how much your camera costs, but how skillfully it is used to create the image perceived in the imagination and in the mind."

- Chris Weston

Being able to capture correct amount of light is what makes a good photo and if one is able to get the composition right, it would result in a great picture.

I would like to share few points about the two basic parameters, which are useful in controlling the amount of light captured by the camera sensor. These two basic controls are aperture and shutter speed. It's very important to know the relation between these two parameters and the light captured. In the field of photography, light is measured with a unit called exposure value (EV). Let's know how to control EV by manipulating aperture and shutter speed.

Shutter speed: Shutter controls the duration of exposure i.e., the duration of time the sensor is exposed to light. It's measured in seconds and fractions of seconds whose range in a a typical camera is from 30 sec to 1/4000 sec. So reducing the shutter speed from 1/125 sec to 1/250 sec halves the exposure duration i.e, decreases the EV by one stop and vice versa.

Lens Aperture: Lens aperture controls the amount of light passing through to the sensor by increasing or decreasing the size of the pin hole created by the diaphragm in the lens. In this case, doubling the area of the pin hole doubles the quantity of light and hence increases the EV by 1 stop. This is referred to as f/stops or f/numbers (f->focal). To make it simple, f/4 indicates that the ratio of the lens focal length to the area of the pin hole is 4. i.e., aperture size is 1/4th of the focal length of the lens. So lower the f/number more is the aperture size and hence more light will pass through to the lens.

Reciprocity: If we double the quantity of the light passing through to the sensor (by increasing the lens aperture), then we must halve the duration of exposure (increase shutter speed) to maintain the same exposure value (EV).

Being said this, the most important thing is to plan for the perfect picture. Imagination and visualization are great assets to take some wonderful snaps. To be there at the right place and at the right moment takes something on your part but if you have patience and are able to get the composition right, you are surely on your way up the ladder..!


Image details: Gopal waiting for the perfect moment to capture the sunrise!!
Nikon D40 SLR, 18-55 mm lens @ 55 mm, f/8, 1/100 sec, ISO-200