By Steve Alexander

Q: I haven’t been able to send my iPhone photos to Walgreens and Walmart for printing due to a format issue — the photos were in the HEIC (High Efficiency Image Coding)file format the iPhone uses. I then saved the photos in the JPEG (Joint Photographic Experts Group) file format the stores wanted, but I was told that some JPEG photos also aren’t accepted. What can I do?

—Thomas Elwood, Bedford, N.H.

A: The photo printing services of Walmart and Walgreens require you to send them photos in the JPEG (also written as JPG) file format, which is widely used by digital cameras. The main restrictions are that Walmart won’t accept any photo larger than 16 megabytes (see tinyurl.com/4ne5w4ha), and Walgreens discourages sending a photo larger than 20 megabytes (see tinyurl.com/pez3kt25). These limitations probably won’t affect you; iPhone JPEG photos typically contain less than 10 megabytes of data.

The HEIC photo format (Apple’s version of the standard HEIF, or High Efficiency Image Format) was designed to save storage space on iPhones. HEIC photos require only about one-third as much storage space as JPEG photos. The drawback to HEIC is that some photo-printing services and non-Apple devices don’t use that format. So, since 2017 Apple has let you choose which format your iPhone should use for photos. To pick one, go to Settings, click on camera, then click Formats. Choose “high efficiency” for HEIC or “most compatible” for JPEG.

If you’ve already taken a lot of photos using HEIC, there are plenty of programs that can convert them to JPEG (see tinyurl.com/f3tkzd or tinyurl.com/373buv84). In addition, online file storage services such as Dropbox and Microsoft OneDrive can convert your HEIC photos to JPEG format when you upload the pictures from your iPhone.

Contact Steve Alexander at steve.j.alexander@gmail.com. Please include a full name, city and phone number.