Apple has been keeping up with upgrading its smartphone features. The tech giant now boasts its latest devices available in two different sizes and an impressive refocusable camera.

Apple may issue iPhone 6 with two different screen sizes -- one similar in size to the current model and another incoporating a much bigger screen, pushing their current line of smartphones to phone-tablets.

"Apple's 2013 focus was a less expensive iPhone to go alongside its standard flagship offering, while 2014 development will center around a bigger display," a source said. "Apple is reportedly testing a variety of different prototypes. All of the reports have indicated a size ranging from 4.7 to 5.7 inches."

"There may be multiple models, just as we saw with the iPhone 5S and iPhone 5C," the source added. "We may be looking at a 4.8-inch 'standard' model to replace the iPhone 5S and a larger 5-inch to 6-inch model as a phablet competitor."

The supposed features of the next iPhones are supported by one of the recent patents that Apple was awarded: it was alleged that Apple is investigating the possibility of a refocusable camera shooter for the next-generation iPhones, improving further on the optical image stabilization. In other words, the new devices will include the light field camera that allows users to refocus image even after they have already been taken, and the camera will be able to capture images' light fields.

In addition, the advanced camera feature gives iPhone 6 shooter 3D capabilities that enable users to capture videos and clips in 3D. The function will be mixed with facial recognition on the front portion, which should strengthen the security of iPhone users.