Labeling sequences is paramount.

The process of painting a canvas is personal and unique to each artist. Visitors step through the sequence which Philip Pearlstein used to paint a wedding portrait. (WebExhibits) View a the sequence of layers in an Incan mummy. (National Geographic)

Problem

You need to display a time-lapse sequence, or a sequence of images, such as before and after views of deforestation, the development of an embryo, a flower opening, or MRI or PET slices of the brain.

Solution

Allow the visitor to choose a frame in the timeline sequence by using one of two methods:

• Slider: Use a slider with a knob to choose a point in time. The track for the slider should have markings to indicate that there are discrete steps.
• Filmstrip: Display a strip of thumbnails, like a sequence of film. The visitor points at the thumbnail and sees the larger frame.

Discussion

In this technique, the relationship between the frames is emphasized. Good interfaces have measurements on them, with a labeled axis. For example, if exploring a tide, label the axis with times (low tide, medium time, high tide); if looking at MRI slices, label the location within the brain. If the sequence is a loop, such as a rotating planet, instead of a linear slider, use a circular slider, and track the knob in a continuous fashion.