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Demystifying iCloud Photo Library

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iCloud Photo Library is the glue that connects the Photos apps on iOS devices and the Mac, but from the beginning it's been a cloud full of questions. Jeff Carlson, author of Photos for OS X and iOS: Take, Edit, and Share Photos in the Apple Photography Ecosystem, cuts through the fog about Apple's photos-everywhere service.
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iPhoto was certainly getting creaky over the years, but it wasn't age that prompted Apple to replace it with the brand new Photos for OS X. Now that so many millions of us use iPhones and iPads (and the occasional iPod touch), we're shooting and viewing photos everywhere.

One of the biggest selling points of Photos for OS X is iCloud Photo Library, a service that ties together the Apple photography ecosystem, allowing you to view your entire photo library on whatever device or computer you like. Doing so requires a lot of pieces that must work together. If you're thinking of turning on iCloud Photo Library, follow along with the questions and answers in this article to learn iCloud Photo Library's strengths, weaknesses, and important details.

Do I need to store my photos on iCloud?

No. Apple touts iCloud Photo Library as one of the most important features of Photos for OS X, but the service is not required to use the application. Just as iPhoto and Aperture did before it, Photos stores your photo library on your hard disk.

Initially, iCloud Photo Library is not enabled—you need to turn it on deliberately. If you have no interest in sharing your photos on other devices, you can ignore iCloud Photo Library entirely.

Do I need to buy more iCloud storage?

Your free iCloud account includes 5GB of storage, which is shared among all iCloud services (such as saving documents in Pages or Numbers). If your Photos library exceeds 5GB, you'll have to pay a monthly fee for more storage. Here are Apple's fees in the United States (international prices can be found here):

  • 50 GB: $0.99
  • 200 GB: $2.99
  • 1 TB: $9.99

The Photos app won't let you turn on iCloud Photo Library if your library exceeds the limit to which you're subscribed. To check the size of your library, choose Window > Info and make sure no photos are selected. The size appears in the Info window (see Figure 1).

Figure 1 Checking the size of the Photos for OS X library.

How does Photos fit my entire photo library on my iPhone?

Even if you own an iPhone or other iOS device with 128GB capacity (the highest at the time of this writing), that's probably not enough space to store your entire photo library. To get around the storage limitation, Photos keeps much smaller optimized versions on the device. The original, full-size versions are stored on Apple's iCloud servers.

Those optimized versions make it easy to see thumbnails of all your photos. When you view one in more detail, a small progress wheel appears while the high-resolution version is fetched from iCloud.

In fact, Photos for OS X can also store optimized versions of your images on the Mac; for example, if you have an iMac at home and carry a MacBook Air with limited storage when you travel. In the preferences for Photos for OS X, click the iCloud button and choose Optimize Mac Storage (see Figure 2).

Figure 2 Optimize photos on your Mac to save storage space.

What happens when I edit a photo using a different app on my iPhone?

In addition to having a copy of each photo on all your devices, you can edit a shot and expect the adjustments to appear everywhere, too. There's a slight twist, however.

The editing tools in the Photos app on iOS devices include features such as cropping, applying filters, adjusting light and color, and converting to black-and-white. Those same tools exist in Photos for OS X, too, but on the Mac, you'll find even more controls—such as adding vignettes, changing white balance, sharpening, and spot-retouching areas.

When you edit using the basic tools found on iOS, those same values shift to the Mac, too. For example, if you change the Shadows level on the iPhone to +0.24, the same control on the Mac will also be set to +0.24 (see Figure 3). That capability allows you to fine-tune edits no matter which device you're using.

Figure 3 Adjustment values transfer between Mac and iOS versions of Photos.

But there's a glitch that I hope Apple resolves in a future update: If you apply an adjustment on your Mac that isn't offered in Photos for iOS, such as a vignette, the values of the controls are reset to zero on your iPhone (see Figure 4). The adjustments you made are not removed—a photo you made brighter by increasing the Exposure setting is still brighter than the original—but further modifications start as if you were editing the image for the first time. That's not a deal-killer, but it can be annoying if you're frequently jumping between Mac and iOS for image editing.

Figure 4 Adding a vignette on the Mac resets the Light adjustment sliders on the iPhone to zero.

Final Thoughts

With the exception of that last editing detail, I've found iCloud Photo Library to be quite useful. It really does make a difference when you can use any device to show someone a photo that you captured years ago.

Author and photographer Jeff Carlson (@jeffcarlson, is the author of Photos for OS X and iOS: Take, Edit, and Share Photos in the Apple Photography Ecosystem (Peachpit Press) and Take Control of Your Digital Photos on the Mac (Take Control Books), among many other books. He's also a columnist for the Seattle Times, a contributing editor at TidBITS (, and writes for publications such as Macworld and

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