Brightness vs Contrast
Brightness and contrast are two very important topics discussed in the fields of optics, photography, astronomy, astrophotography, instrumentation, spectroscopy and various other fields. Brightness can be defined as the luminance effect a source or an object makes on the observer. Contrast can be roughly defined as the color separation between two different colors which are identifiable. Both of these concepts are very important in understanding a number of fields which have usages of these concepts. It is vital to have a proper understanding in these concepts in order to excel in fields such as photography and optics. In this article, we are going to discuss what brightness and contrast are, their applications, the similarities between brightness and contrast, the definitions of brightness and contrast, the physical significances of brightness and contrast, and finally compare brightness and contrast and highlight the difference between both.
Brightness
Brightness is a very important quantity discussed in photography and astronomy. In photography, brightness is the luminance effect created by a light source or reflected light. Brightness is a visual perception which enables the observer or the viewer to see an image as bright or dark. A light source or a light reflector is considered as a bright spot whereas a light absorbing surface is known as dark.
The brightness is often quantified using the RGB scale. RGB scale, which stands for Red, Green, Blue scale, is a three dimensional color space where any color can be quantified using the R, G, and B values of the color. The brightness, often denominated using the symbol µ, is quantified as
µ = (R+B+G)/3, where R, G, and B are corresponding Red, Green and Blue values.
In astronomy, brightness is divided into two types. Apparent magnitude is the brightness of a star observed from a given location. Absolute magnitude is the brightness of a star observed from 10 parsecs (32.62 light years).
Contrast
Contrast is the property of an object or representation of an object in an image which makes it easy to distinguish from others. These qualities are luminance and the color of the object. In real life, contrast is identified as the brightness and the color of the considered object with respect to the other objects in the field of view. Contrast is a very important aspect used in optical character recognition. Images with high contrast are easier to recognize than those with low contrast.
There are few methods to measure contrast. The Weber contrast is defined as (I-Ib)/ Ib, where I is the luminance of the object and Ib is the luminance of the background.
What is the difference between Brightness and Contrast?
- Brightness is an absolute quantity which only depends on the R, G, and B values of the given image. Contrast is a relative quantity, which depends on the background in which the object is placed.
- Contrast is the quantity that effects object recognition than the brightness.
- The contrast of an object depends on the brightness of the object itself and the brightness of the background, as well as the colors of the object and the background.