Comment 3 for bug 919385

Yes, the whole point of zoom-out is for the image to get smaller and no longer fill the whole canvas. Under some circumstances, that is a good thing.

What is the use case? Sometimes you want to look at the photo without being distracted by various user interface widgets right next to it. Zooming out helps you to do this. Strange as it sounds, even though the photo is a little smaller, if it's got a little "breathing room" with no visual distractions near it, you can sometimes see it better. Fullscreen mode can do this sometimes, but it's not always the best approach.

Shotwell may not be a full-fledged image viewer, but part of a photo manager is deciding which photos to keep, and which to delete. The way you do that is to view the photos. If the viewer is really bad (hypothetical example: a horrible scaling algorithm, and displayed colors that are way off), then the user is making decisions with poor information, and will make poor decisions on what to keep or delete. If the viewer is average, then the user has better information, and will make better decisions. If the viewer is great, then the user has even better information, and their decisions will be that much better.

Yes, we are talking about an effect that is fairly small. A detail. But details add up, and lots of good details can really make a difference.