Controls for Light

Technically it is about a method of controlling and using the Light. Easy to cover the techniques so I'll get them past you first. Two fundamental categories here.
First is to modify/control the light you have. A vast topic where people's creativity comes out and we keep seeing new ways to accomplish this every day. Few of the more popular ones are listed to give you an idea.

• Moving under a shade to reduce the light
• Using reflectors or diffusers to change the nature of light
• Using strobes or flash to add light. Adding flash gels or gobos to change the light from the flash

Second category is to set your camera to control the amount of light it receives from a scene. Being an engineer, the second category is easier to explain. Also, it is easier because no matter what camera you have, there have always been only three ways to do it. These are given below in the order in which they act on the light entering a camera body.:

1. Aperture Size: Entry point for light in the body is the camera lens and aperture is a circular opening in the lens. The diameter of the opening can be varied to allow less or more light in the body.
2. Shutter speed: Shutter is the gate that sits in front of your digital sensor or the camera film. It is a gate between the light coming from the lens and the sensor of the camera. It opens and closes to allow the light to fall on the sensor that converts the light in to pixels and store it as an image. Shutter speeds on most cameras have a range of around 50 msec to 30 seconds. This for most cameras is the control element that provides the most flexible control for light.
3. ISO setting: A property and setting for the sensor that sets the sensitivity to light. A smaller number means less sensitive to light. Hence, the same amount of light at ISO 100 will produce darker image than at ISO 400 (4 times darker). However, ISO changes don't come for free as aperture and shutter speed settings mostly do. Increasing ISO always increase the noise in the image. However, with today's technology sensors handle noise very well and one can get usable images from cameras even at ISO 800. Still, bumping up the ISO should only be considered after exhausting options with aperture size and shutter speed.

It is the second category that photographers have the most control over and although it appears that there are only 2 variables to play with ( the third one, ISO setting should be kept at the lowest possible setting), it is still a very complex equation to balance. The same shot can usually be acheived by multiple combinations of aperture and shutter settings. It is the skill of a photographer to know what is the best combination of these two settings that will produce the desired result. More on that in some later post...