While Magic Mouse is really cool, it is not really the best bet for a Photoshop user. Read here: http://store.apple.com/us/question/answers/product/MB829LL/A?pqid=QXF99PAC4UX2C4PDCFTTP4XP YXH2YTDFC
Other than that, you can press 'Option' key on your Mac keyboard and use the 2 finger zoom on Magic Mouse to zoom in. But, I doubt if this will give you even step zoom.
The other keyboard combination you could use (I'm sure you're probably already aware) is Cmd + & Cmd - key combination which will give you equal step zoom.
You can also take a look at this article: http://creativetechs.com/tipsblog/11-ways-to-zoom-in-photoshop-cs4/
Even though it is for CS4, it works across all versions of Photoshop (so far).
Thanks for the answer. However, it didn't answer my question about scrolling with even steps on a mac. Anyone else?
You'd tried Option+Shift as well?
Or unchecking zoom with scroll wheel and Option+Shift?
You might have to get another mouse such as a Logitech.
Thank you for your attempt to solve my problem. As far as I'm concerned I've tried all reasonable key combinations while zooming, both with the "zoom with mouse scroll" turned on and off - but with no luck.
Now, I had a chance to plug in another mouse (Logitech MX518) and guess what happened? Holding shift while zooming works in even steps! So this problem is all about the Magic Mouse. I'm a bit overwhelmed by the fact that the scroll doesn't work as it's supposed. I guess it has something to do with the ability to scroll smoothly, and that's probably an opportunity cost for the inconvenience of not being able to scroll in steps.
I have to seriously consider buying a new wireless mouse with proper scrolling features.
Thank you all for your replies, on my behalf this case is closed.
I told you this in my Reply# 1 but for whatever reasons, "it didn't answer your question"!
Anyway, glad you've found a solution - of buying another mouse.
I think this is complete nonsense. At home, I use CS5 with my Magic Mouse, and it works great. Opt + Shift + Scroll, and I get nice incremental steps: 50%, 66.67%, 75%, 100%. At work, I have this "awesome" new version of Photoshop CC, and the zooming is completely whack. I hate Adobe so much. I'm actually surprised more people haven't complained about this. I'm sorry, but I shouldn't have to buy another mouse to use Photoshop. That's ridiculous.
Please tell me I'm not the only one suffering from this.
It must work for some people with photoshop cc or there would be a lot of posts on the subject, which there haven't been.
I don't use a magic mouse, but if you compare your mouse settings in the system preferences between the two systems maybe you'll find something.
Are both systems the same version of mac os x?