The 1000 most recently imported photos in your iPhoto library are automatically uploaded to iCloud and added to your Photo Stream.
If you prefer to choose which photos from your iPhoto library are added to your Photo Stream, you can turn off automatic uploading and add photos to Photo Stream manually.
Photos taken with an iOS device in your Photo Stream, photos saved to the device’s Camera Roll, and photos imported to your iPad using the Apple Camera Connection Kit are uploaded automatically. You can’t manually add photos from your device’s Camera Roll to Photo Stream.
Note: Only image files in JPEG, PNG, TIFF, or RAW format can be uploaded to Photo Stream.
To turn off automatic uploading to your Photo Stream:
Choose iPhoto > Preferences, and then click Photo Stream.
Deselect the Automatic Upload checkbox.
To add photos to your Photo Stream manually:
You can add photos manually from your iPhoto library to your Photo Stream whether automatic uploading is on or off.
Do one of the following:
In iPhoto, drag one or more photos from Events, Photos, Places, or Faces view to Photo Stream in the Source list.
Select one or more photos, and then click the Share button in the toolbar and choose Photo Stream from the pop-up menu.
Select one or more photos, and then choose Share > Photo Stream.
The photos are uploaded to your Photo Stream and can be viewed on all the devices in your Photo Stream.
Photo Stream can contain up to 1000 photos. When you add a new photo to Photo Stream after you reach the 1000-photo limit, the oldest photo is removed.
Photos remain in your Photo Stream for 30 days, and are then removed automatically.
Individual photos can’t be deleted from your Photo Stream in iPhoto, but you can sign in to your iCloud account, reset your entire Photo Stream—permanently removing all photos—and start over. For more information, see iCloud Support.
WARNING: Resetting Photo Stream permanently removes all your photos from iCloud. To avoid losing any photos, make sure you’ve imported them into your iPhoto library or saved them to an iOS device before resetting Photo Stream.