Philosophy

For the most part, a new look for an operating system doesn’t need to justify itself. It’s fashion. We all want something new every once in a while. It just needs to look good. But things start to get complicated when fashion butts heads with usability—then we want reasons.

Though I’ve tiptoed around it thus far, the friction point in Yosemite’s new visual design is its pervasive use of transparency. (Technically, “translucency” is more accurate, but please indulge my idiomatic usage.) Allowing what’s behind to influence the appearance of what’s in front is problematic in a couple of ways. From a purely aesthetic perspective, transparency is unpredictable. Designers can decide which aspects of the background will influence the foreground image, but they can’t control the content of that background. Will its contribution make the final image more pleasing, or will things turn ugly?

In terms of usability, transparency risks impairing readability and recognition. Colors bleeding through from other content can undermine the intended contrast between text and its background. Symbols and shading meant to subdivide an interface can be sabotaged by the influence of unrelated background images. The content as designed by the application developer is the signal; any background content that shows through is noise.

This is not Apple’s first transparency rodeo, however. Early versions of OS X faded some interface elements almost to the point of invisibility. The look made for a nice demo (14 years ago, anyway), but readability was severely compromised in some cases. The problem was exacerbated by the lack of additional image processing (e.g., blur) applied to the background. (At this point in OS X’s history, all compositing was done on the CPU.)

Later versions of OS X toned down the transparency and eventually incorporated additional effects to make background content even less distracting. In Leopard, Apple once again succumbed to the siren call of transparency, deciding the world really needed to see more of what’s behind the menu bar. In another repeat of history, pre-release builds of Leopard included even more extreme transparency, which was moderated before release. (Menu bar transparency was eventually made optional in 10.5.2.)

Apple has taken great pains in Yosemite to ensure that any content that does show through transparent interface elements is extremely diffuse and indistinct. But the aspects of the background that do show through—mostly color—are often magnified.

Inevitably, I find myself searching for a reason. Why is it important for me to see any aspect of what’s behind the front-most active window? Why risk reducing both the usability and attractiveness of the UI? To what end?

Apple has offered many different justifications for this aspect of Yosemite’s new look. In the WWDC keynote, Craig Federighi explained in-window blending in the Finder—icons scrolling “behind” the toolbar—by saying, “The use of translucent materials gives you a sense of place as you scroll your content.” Given the disappearing scroll bars introduced in Lion, a vague, colored haze showing through the toolbar may indeed be the only indication that more content is available above the currently visible region, but I’m not sure how strong that signal will be to most people.

Federighi also described translucency as a tool for visual customization. “Now your windows take on the personality of your desktop. As you change your desktop picture, your window adapts to reflect that personality and that temperature.” This works best if there’s nothing between a window and the desktop background. The strongest influence on the “personality and temperature” of a window on a busy OS X system is the content of some other window, which is more difficult to control than the desktop picture.

(The most obvious demonstration of this aspect of vibrancy is the menu bar. It pulls color from the desktop picture behind it, but this color also appears in each pull-down menu. Even if a completely white window is behind a pull-down menu (or any other vibrant surface), it will be tinged with the color of the desktop background.)

In a later WWDC session, Mike Stern, a User Experience Evangelist at Apple, espoused the idea that software interfaces should have plausible physical dimensionality and that this dimensionality helps the user “to focus on the things that are in the foreground and pay less attention to those things which are in the background.” Stern noted aspects of OS X’s design (like gradients and drop shadows) that contribute to dimensionality, but he also cited the use of transparency in elements like Notification Center.

I don’t think Notification Center, menus, and the Dock need to be transparent for me to understand that they’re on top of the other things on the screen. Even setting aside the drop shadows, the fact that these interface elements are drawn on top of everything else gets the point across just fine.

There’s a kernel of truth in Apple’s justifications for the widespread use of transparency in Yosemite. Surprisingly, the one I find myself agreeing with the most is transparency as a vector for personalization—or, at the very least, variety. As noted earlier, the Yosemite interface really does look quite different depending on what’s behind the various translucent interface elements. I’m not sure how much control users will have over this aspect of the experience, but at the very least, the desktop picture can spread its tint to all vibrant surfaces while also strongly influencing the menu bar and the Dock (assuming people don’t slide windows behind it).

As much as I may support any of these lines of reasoning, my tolerance for any instance of impaired readability due to background “leakage” is very low. Others feel differently, I’m sure, but I find myself wishing that Apple had chosen an attractive, signature look for “non-transient” elements like windows and sidebars that was based on completely opaque artwork. Interestingly enough…