Actually
Solution: Create a smart library in iPhoto called videos then select all the videos in iPhoto and ”Drag and drop” the videos from iPhoto to an empty folder on your mac.(Do not use the export function from the menu) Next open photos and import the videos and that’s it you will see that the videos have the correct time stamp. You can drag and drop your pictures from the Photos app to the Desktop, or you can use the Export menu (in the File menu). Cute dog, great quality export. Screenshot: Rob LeFebvre/Cult of Mac. Photos app for Mac groups all of your photos in a large library file. Photos app does not have the 'Open In' feature, which is used to open a photo in another app. You must export the photo from Photos app before opening it in another application. If you want to export photos from Photos app, select your photo and go to 'File' menu and then.
I had the same problem but looking around on google I found out that there's an export status bar. ( I use MacOS Sierra 10.12.1). https://qhwopca.weebly.com/one-password-app-mac.html.
I found this post Best photo book making app for mac.
and one reply says that the export status is found by going on the 'Photos' section on Photo (top option on the left menu)
There, if you are undergoing an export operation, you can see a small pie next to the small-large photo size slider.
The pie gives you an idea of how much you have exported, but if you click on it you get the exact figure.
Not easy to find, but it is there..
Mac Photos Import Videos
Export Pictures From Photos
Mac Photos App Download
Ciao!