Q: How do you change opening application from preview to I photo

iPhoto (and Photos) do not "open" image files. They store them in a Library. You can view the images in the Library from iPhoto (Photos), but you can't open files separately.

Import the image file into iPhoto and then view it in iPhoto.

Hi Bake904. You can change which app an image file opens with for just that image or for all images of that type.

1. Click the image file to highlight and press the Command-I keys to open an information window.

2. Click the Open with double-arrow indicator and click Other if you don't see iPhoto listed.

3.  Scroll to iPhoto. Select Always Open With if you want the image file to always open with iPhoto. Click Add.

4. If you want all image files of the same type to open in iPhoto, Click Change All.

5. Click Continue to accept the change.

6. Control-click the image file and move the cursor to highlight Open With to see that it is now the default app.

OS X Yosemite: View file, folder, and disk information

OS X Yosemite: Choose an app to open a file

Remember that doing this does not open the file. It imports it to the iPhoto database. iPhoto is not an image viewer like Preview is, it's a database driven Photo manager.