Apple on Friday faced a lawsuit accusing it of promising more available storage space than it actually delivers in iPhones, iPads, and iPod touch devices.

The suit filed early this week in US District Court in Northern California argues that while Apple touts 16 gigabytes of digital storage on lower price models of gadgets such as hot-selling iPhones, about a fifth of that is eaten up by the latest operating software.

The percentage of advertised space available for digital content such as photos, video, or music shrinks further when Apple gadgets built with eight gigabytes of storage are considered, the suit filed on behalf of two Florida men maintained.

The suit charges Apple with being deceptive in advertising that represents devices as having much more storage space than is really available to people who purchase devices.

Once Apple gadget owners reach limits to data storage, the California-based technology titan prompts them to pay monthly fees for digital locker space online at its iCloud service, according to the lawsuit.

"Using these sharp business tactics, (Apple) gives less storage capacity than advertised, only to offer to sell that capacity in a desperate moment, eg when a consumer is trying to record or take photos at a child or grandchild's recital, basketball game or wedding," the lawsuit maintained.

"Each gigabyte of storage Apple shortchanges its customers amounts to approximately 400-500 high resolution photographs."

Apple offers all iCloud users five gigabytes of free storage, which arguably offsets the amount that the lawsuit contends is eaten up by the operating system.

Attorneys behind the suit are seeking class action status along with punishments that include Apple turning over all profits from sales of gadgets at issue in the case.

Apple declined to comment for this story.

A suit filed in a trial court in Canada regarding how up front Apple was being with the actual amount of storage space in devices was dismissed. That dismissal was upheld on appeal in early 2012.