Improve iPhoto5 performance by setting thumbnail size

Feb 16, '05 09:22:00AM

Contributed by: jaysoffian

Currently, my iPhoto library is over 30GB and 10,000 photos. Its performance has been so dismal, even on my dual 2Ghz G5 (1GB RAM) that I've seriously thought about dumping it altogether. But before I did that, I thought I'd try dividing up my library into multiple smaller libraries. After I split off my first library, which only had my 2005 images in it, I was surprised to find iPhoto's performance wasn't a whole lot better. So I did some poking.

When you import photos, iPhoto creates a thumbnail for each image. This thumbnail is 240 pixels wide by however many pixels high are appropriate to retain the original aspect ratio. You'll find these files in the iPhoto Library/YYYY/MM/DD/Thumbs folder, and you can open them in Preview to see their size. What I finally realized is that when you're in the Organize view of iPhoto, if you keep the photo size slider so that the images are no larger than the thumbnails (about 3/4ths of the way over), iPhoto is *much* faster than if you move the slider further over.

What I figure is that as long as you keep your displayed photos smaller than the thumbnails, iPhoto loads the thumbnail files and scales those down to the requested size. But as soon as you move the slider to larger than that, iPhoto has to load the original images and then scale them down in order to display the requested size. With the size of my library and my 6 megapixel images, this was causing my machine to start swapping like mad as iPhoto attempted to read in and scale all those images. Since the GUI slider isn't very precise, I played around with setting it to different values via the iPhoto preference file. e.g.:

defaults write com.apple.iphoto ThumbnailSize .80
Ideally you could set this to a value such that iPhoto wouldn't need to scale the thumbnails at all and could just display them as they are on disk, but I was unable to figure out the magic value. It's somewhere between .8495 and .85 though. On my machine, it's pretty obvious whether iPhoto is scaling from the thumbnail file or from the original image.

So anyway, with ThumbnailSize at .8495, iPhoto is fast enough that I'm happy even with my original library of 10k images. Your mileage may vary, of course.

[robg adds: A previous hint for speeding up iPhoto still seems to hold true in iPhoto5 -- get rid of the shadows.]

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