Here are two UI suggestions about the image browser.
First problem:
When in the photolibrary the browser displays a 2D array of photos. Scrolling with the mouse wheel scrolls vertically.
When in the customize tab the browser displays a 1D array of photos. Scrolling with the mouse wheel scrolls horizontally.
That’s inconsistent and annoying in the case where you want to mimic the 1D behaviour but in photolibrary. For example if I display a single line of 5 photos and want to compare the 5th and 6th photos: they can’t appear at the same time in the browser without messing around with the browser organisation. In the customize view there’s no such problem! Maybe you could detect that only one line is displayed and map the scrolling differently in that case?
Second problem:
Scrolling is not smooth !
In photolibrary it changes the first displayed line: that makes sense as it is intended to display multiple lines. But when trying to display a single line it should behave like in the customize tab.
In the customize tab that’s where I feel some smoothing could be added: it currently scrolls by discrete increments that don’t even seem to be thumbnail-size related. Just scrolling smoothly would be better IMHO.
In the library and in the customize tabs, a user should be able to choose between 1D strip or 2D array of thumbnails. The size of the thumbnails should be adjustable in both cases.
For now, you can get a 2D array in Customize by undocking the image browser. The thumbnail size is adjustable in both views in Customize and in PhotoLibrary also (which only presents a 2D array).
In Photo Library, when user presses Cntrl while scrolling the mouse wheel, the thumbnails resize; however, if you do the same in the Customize tab, the thumbnails do not resize.
An annoyance with the current implementation: if user selects an image in the browser, and then zooms-in the thumbnails view, then the selected image will move out of view if other images are ahead in the sorting sequence of the image explorer.
Before this topic becomes a catch-all for everything “wrong” with the filmstrip (it’s a votable topic for a single feature request): I suggest searching the forum for the word “filmstrip” - you will find a large number of topics discussing these different behaviors and suggesting changes.
For those wondering: if you want to resize the thumbnails in PhotoLibrary, just grab and drag the separator between the image viewer and the filmstrip.