If you have spent a while adjusting a picture to your liking in Photos app for Mac, you can easily apply those image adjustments and edits to other pictures in Photos app as well.
This is accomplished through a handy but little-known copy & paste adjustments ability, and it’s quite easy to use.
Essentially what you’re doing is adjusting one image and then you’ll be copying those adjustments (but not the image) and applying them to another picture. Here is how it works in Photos app for macOS and Mac OS X, using the same copy and paste shortcuts you’re already familiar with.
Open Photos app on the Mac
Double-click on any picture and choose “Edit” as usual, then make adjustments to that picture as you typically would (adjustments to brightness, color, sharpness, vignette, etc)
When satisfied with the image adjustments, go to the “Image” menu and choose “Copy Adjustments”
Now return to the primary Photos app browser and open another picture, then choose the “Edit” option again for the new picture
Go to the “Image” menu again, this time choosing “Paste Adjustments”
The image adjustments made in the prior image edits are now applied to the picture
Repeat for additional pictures if desired
This offers a really great way to apply bulk image color corrections and other fine image adjustments to many pictures.
At the moment there is no ability in Photos app to select multiple pictures and paste adjustments across them, but perhaps a future version will enable that as well.