If it is just a few pictures then manually will be the most effective way. If there are numerous duplicates then there is a free iPhoto AppleScript to Remove Duplicates (See links below) or Duplicate Annihilator (paid for software).
Yes, you can permanently delete photos from the iPhoto library. Please watch the following video which describes the process. http://www.woopid.com/view_video.php?viewkey=80425104
Only the iPhoto software is replaced when updating to the new version; your library of photos is not touched.
Iphoto cannot retouch photos, it only just got the capability to play videos on the app.
Unfortunately you cannot transfer photos off Facebook into iPhone. It only works one-way; iPhoto to Facebook.
When the device is plugged into the Apple computer an icon will appear on the desktop. Open iPhoto and drag the photos to that icon. They will then be compied to that device.
What's good about Picasa iPhoto, is that you are easily able to upload your own photos into the program and create beautiful web albums! Another fantastic thing is that you are able to upload photos from iPhoto, which is an Apple product
Sync with Mac, photos are uploaded to iPhoto. Export photos to flash drive.
What is the means of on the screen? desktop? In the mac store, there are many free or paid software to help finding duplicate files, include duplicate photos, such as photo sweeper, cisdem duplicate finder for mac, etc. All of them can find duplicate photos well. Of course, if there is litter duplicate photos, there is no need to use the third part software.
You have to hook it up to itunes and iphoto
iPhoto is no longer available for download as it has been discontinued by Apple. However, you can use the Photos app that comes pre-installed on macOS devices as the replacement for iPhoto.
The best way would probably be to get a hardware specialist to download the photos of the main drive of your iMac.
To see a hidden picture in iPhoto select Hidden Photos from the View menu. You can then right click on the picture and select Unhide Photo from the menu that appears to prevent the picture from being hidden.