NPR’s Planet Money made a big splash with its immersive Planet Money Makes A T-Shirt project last month, which looked at the path a shirt takes from conception to production.

There was no shortage of rich imagery in the project. Over at Source, NPR visuals team member Alyson Hurt talks about the decision to pass over GIFs in favor of creating filmstrips with JPEGs and some CSS animation:

For NPR’s “Planet Money Makes A T-Shirt” project, we wanted to experiment with using looping images to convey a quick concept or establish a mood.

However, GIF as a format requires so many compromises in image quality and the resulting files can be enormous. A few months ago, Zeega‘s Jesse Shapins wrote about a different technique that his company is using: filmstrips. The frames of the animation are stacked vertically and saved out as a JPG. The JPG is set as the background image of a div, and a CSS animation is used to shift the y-position of the image.

Last fall, we wrote about Zeega’s quest to replace the GIF with their own .jpeg-based ZGA format.

If you’re curious about how the visuals crew at NPR made the filmstrip, check out Hurt’s post for a detailed step-by-step.