The Ins And Outs Of Exposure

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What is through the lens light metering

‘Through the lens light metering’ is something featured on most DSLR cameras in order to measure the amount of light entering the cameras lens.

This feature on cameras helps to insure that our images are correctly exposed. If there is too much light the image becomes over exposed and if there is too little light the imaged becomes underexposed.

How to control exposure

to control the amount of light entering the cameras lens you can change the: Aperture, ISO or shutter speed

How it works

  1. light is reflected from a scene or subject and then through the lens (this can be natural light such as the sun or artificial light in a studio)

2.Then it hits the mirror in front of the imaging sensor and is reflected up to the camera’s focusing screen and metering sensor

 

The light meter reading on a camera is measured from -3 to +3

0 indicates a correctly exposed image. A Minus readings ( so -3, -2 or -1) means there’s not enough light and the outcome will result in an underexposed image (an image that is too dark).

A positive  reading ( so 1, 2 or 3) means the camera is exposed to too much light so the outcome will be an overexposed image (an image that is too light).

 

On cameras, the light metering is usually located in only two areas.

On some camera its on the LCD screen and sometimes its on the screen on top of the camera.

To make the scale present you either press the info button on the body of the camera or turn the function dial to settings

 

UNDEREXPOSURE

An underexposed image is a photograph that is considered to be too dark.

When an image is too dark the details of the subject are lost in the shadows. For example the top image on the right, the architectural details in St Paul’s are lost due to the lack of light.

On a camera there is a light meter in order to help you get a correctly exposed image. An underexposed image reads in the negative area like this:

To change underexposure you can adjust the shutter speed and aperture on the camera.

If the image is underexposed you would change the aperture so the lens is bigger and allows more light in. Then you would change the shutter speed to a slower setting so the camera has a longer period of time to let more light in.

For a correctly exposed image you would keep adjusting these variations of the shutter speed and aperture until the arrow on the light meter is out of the negatives and onto the zero.

OVEREXPOSURE

In photography, overexposure is a term used to describe the process of exposing film to too much light, which results in the photograph being too bright.

When an image is overexposed details are lost in the white. For example in the bottom right picture, details in the girls face are lost – Their noses aren’t defined an blend into the face.

On a camera there is a light meter in order to help you get a correctly exposed image. An underexposed image reads in the negative area like this:

Overexposure happens when the camera film is exposed to too much light. To change this you can adjust the shutter speed and aperture on the camera.

If the image is overexposed you would change the aperture so the lens is smaller and allows less light in. Then you would change the shutter speed to a faster setting so the camera has a less time to let  light in.

For a correctly exposed image you would keep adjusting these variations of the shutter speed and aperture until the arrow on the light meter is out of the positives  and onto the zero.

 

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