Shutterfly’s rival: Amazon

Amazon.com Inc. introduced a photo printing service, triggering the worst single-day decline in more than eight years for shares of Redwood City’s Shutterfly Inc.

The AmazonPrints service offers printed photos starting at 9 cents each and photo books starting at $20. Cards and calendars will be additional options coming soon, according to the company’s website.

Amazon’s news in advance of the fourth quarter, when Shutterfly makes about half of its revenue from customers printing holiday cards and calendars, “couldn’t come at a worse time” for Shutterfly, said Victor Anthony, an analyst at Axiom Capital Management who follows both companies.

Shutterfly didn’t immediately respond to requests for comment.