By default, iPhoto opens when you plug in your iPhone or any other iOS device or camera. But maybe you don’t want it to open. Or maybe you want to load a completely different app like Picasa. This setting is held in two different places, and I can’t quite figure out precisely how they interact. iPhoto preferences has an option to either load iPhoto, Image Capture, or no application. But the Image Capture application has a per-camera setting that allows you to load any application you want. Changing it in one place sometimes changes it in the other but not always.
iPhoto. In the iPhoto menu > Preferences > General tab, you can set the option for “Connecting Camera Opens”. In iPhoto you have limited choices for which app opens.
Image Capture. Open the Image Capture program (in your Applications folder or you can do a Spotlight Search for it). Connect your device. If you don’t see the settings in the bottom left corner of the window like my screen shot below, click the little arrow in the box. In this area you can choose any application to open that you have installed.