Light

Light is the language of photography.  It determines how we take a picture. 

Sensors on cameras are designed to work best in normal daylight.  Lower light levels require the sensor settings to be more sensitive ie a higher ISO setting.  But it's not just as simple as that.  Higher ISO settings introduce more noise into the image and this may be a problem. 

The intensity of light
Brightness varies through the day from dawn till dusk.  The sun is brighter during the day than at sunset or sunrise. Cloudy and foggy days are also darker.  Understanding this is very important as our eyes can adjust for these changes but the cameras sensor can't.

The normal ISO setting for daylight shooting is 100-200.   Increasing this makes the sensor more sensitve to light together with the ability to shoot in lower light.

Measuring brightness
Sensors are less efficient that our eyes at recording the light that is in a scene as they cannot cope with the same dynamic range as our eyes.

Cameras measure brightness using their in-built metering systems. 

There are 3 types:

• Centre weighted
• Matrix
• Spot

Centre-weighted and matrix weight their readings in anticipation of how you would compose and take pictures. Average centre-weighted reading ignores any thin bright strip at the top due to the fact that that is where the sky usually is.

Matrix is far more advanced and takes readings from several points in the image and compares it to a database of similar known types of scene.

Spot is exactly what it says it is - a reading taken of a small area.  This is useful and accurate for certain types of scenes or compositions for exmaple where there is a bright object with a dark background.

The basis for all averaged readings results in a mid tone or 50% brightness or 128 on a scale from 0-255.  However, depending on your scene you which may be brighter or darker than 50% you may need to adjust exposure accordingly.  This can be done by using M mode or the Exposure Compensation control.