07/24/14

The challenge of using area to communicate values in visualizations

Bubble charts are a popular way to present quantitative data. Often the area of the circles in the bubble chart are used to encode the value of a parameter. The larger the value, the greater the area, the bigger the circle. This makes intuitive sense and can be quite effective for rough comparisons. However, it is important to understand that we are not very good at estimating area and  these representations distorts the data because we are not very good at estimating area.
Continue reading

06/10/13

Simultaneous brightness contrast illusion

Our eyes give us a very subjective view of the world. This subjectivity leaves us susceptible to a variety of optical illusions. The fact that we are not very good at estimating the absolute brightness of a region, but have a strong ability to detect differences between neighboring regions causes simultaneous brightness contrast illusions. This type of illusion makes the perceived brightness of any region in a complex image vary depending on the brightness of the region’s immediate surroundings.

The illustration below shows how our perception of a solid grey square is influenced by the background. The two squares below are the same shade of grey, but the lighter background behind the square on the left makes that square appear darker than the one on the right.
Continue reading