By tapping the [+] icons, members of a line can comment on individual photos.

In a household with multiple smartphones, it can be hard to keep track of all the photos from different events. "Email that to me" or "post that one Facebook," is fine, but what if you want to share multiple photos — even whole Camera Rolls — with one another privately?

A number of different apps exist for private photo sharing, but can one app rise above them all to become the Instagram of personal image aggregation? Linea hopes it can.

Linea made the news last week when it closed a $4 million seed round of investment for its image sharing iOS app. A co-founder of Linea spoke to TechCrunch about the funding, explaining the app's niche in the photo app market.

“That sort of one photo at a time is the problem with photo sharing," said Linea CEO and co-founder Rowland Hobbs. "We take so many more photos now and it forces us into this sort of data-management mode — if I’m going to take 10 pictures then I have to decide which one is the best one to put into an album to share with people. And what Linea does with the Mosaic is it get rid of those decisions and focus on viewing all your photos."

We decided to take Linea for a spin to see what all the fuss is about. Aside from being the name of one of my favorite espresso machines, Linea means "line" in Italian so it is fitting that the app starts by asking users to create a "Line" where it will then allow you to put your photos.

Linea allows users to create themed albums called Lines. Users can upload photos to each line by themselves or allow contacts to add photos as well.
Currently, Linea accepts photos from Facebook, your device's Camera Roll, Photo Stream other Lines that you have access to, or straight from your device's camera.

Linea's user interface is easy enough. Navigating through the uploading process is intuitive — you simply tap on the images you want to upload. If you want to put everything on Linea, there is a handy "select all" toggle. Once you have chosen your images, uploading is not the quickest. Even with a wi-fi connection, my photos were uploading at a snail's pace. Luckily, Linea will continue uploading when you press the hold button, notifying you when your upload is going to time out and stop, prompting you to reopen the app to continue.

When your photos are first added to the Line, Linea auto-crops them to fit its horizontally-scrolling grid. If you don't like the placement or cropping of the images in the Line, you can adjust it.

By opening up your Line's edit tool, you can change the orientation of the images in your Line.
In the editing screen, you can swap the placement of photos or remove them completely.

If you want your friends to get in on the action, you can invite them to join your Line. Once they have access, they can upload images to your Line and comment on photos as well. When you have uploaded your photos to Linea, they will be saved in high resolution and can be downloaded to your desktop via Linea's website.

Available without ads for free in the App Store, Linea's big moneymaker seems to be their printing service (though we're not sure how solid of a revenue stream that could be to justify a $4 million round of funding). At any time, you can opt to create a book out of your Line straight from your mobile device. Their 20-page books are $27 for hardcover and $7 for paperback before shipping.

The interface of Linea shines when your device is held in landscape mode—a screen orientation that is not well utilized by popular apps like Instagram and EyeEm.

The idea of Linea is great, but it's not quite ready to become my image sharing app. For one, it would need Android and Windows Phone 8 equivalents so my friends with different operating systems can join my Lines. Once it is available across all platforms, Linea could be the most fun your friends have in a line since the conga inexplicably started at your last birthday party.

Next, I would like to see more photo services to download photos from. It would be nice to put all my Instagram, Flickr, EyeEm and even Twitter photos into a Line. Until then, Linea is a decent photo aggregator and viewing platform that is great for an Apple-only pack of friends.

To test out Linea's horizontally-scrolling slide shows for yourself, download it for free from the iOS App Store.