Hey, Yes adding copyright Logo will protect your photos from being copied.
If you are using an android device, I have a suggestion you to use this app named "Logext: Add Logo watermark and Text sign to photos" from Google Play Store.
The application put copyright logo on picture to safeguard your photo. you can also add copyright trademark logo to the photos with this application. It also allows you to watermark your photos.
It is the best app I have used.
Hope, this helps you out!