Q: How to transfer photos FROM Mac TO devices using Photos

Several ways:  Do you want to transfer all photos your iPhone or iPad or selected albums?

1. You can stream the new photos continually to your mobile devices using "My Photo Stream": iCloud: Photo Stream FAQ
2. You can use iCloud Photo Library to transfer all photos and to keep all devices in sync.
3. You can use iTunes to transfer selected albums from your Photos Library to your iPhone and iPad.

This support document explains the methods 2 and 3:   Keep your photos safely stored and up to date on all your devices - Apple Support

And if you just want to transfer a few photos, mail them or put them onto iCloud Drive.

You cannot from the Photos App, but you can do it through iTunes.

You need to set up the Photo Sync from the iTunes Software, and select the Photos App, rather than iPhoto

cheers,

James

You cannot from the Photos App, but you can do it through iTunes.

This is incorrect

Photos has a number of ways of syncing photos to other devices

The best and only fully automatic way is iCloud Photo Library - iCloud Photo Library FAQ - Apple Support

You also can do all new photos automatically (but not edits r deletions) using MyPHotoStream - My Photo Stream FAQ - Apple Support

and you can do it manually using iTunes sync

LN

To transfer specific files from Photos, select the photos and click on the Share button on the toolbar. (It's the square with the up arrow sticking out of it next to the search box.) You'll see lots of options there.

To transfer specific files from Photos, select the photos and click on the Share button on the toolbar. ...  You'll see lots of options there.

Only most of them are for sharing on social network.  There is not one single option, that will upload photos from a Mac to an iPhone without reducing there size or requiring specific system versions or Wi-Fi.

Mail and AirDrop have already been mentioned.

• To share by Mai lsend the attachments at the original size. and it may require the ability to send by MailDrop, if the image files are large.
• The most elegant way is Air Drop. But you need newer system versions and Wi-Fi. A wired network does not work: Not all models of iPad and iPhone are supported.

https://support.apple.com/en-us/HT204144

To share content with AirDrop, both people need one of these devices using iOS 7 or later, or a Mac with OS X Yosemite or later:

• iPhone 5 or later
• iPad Pro
• iPad (4th generation) or later
• iPad mini or later
• iPod touch (5th generation) or later

You also need to turn on Wi-Fi and Bluetooth. If you want to share with your contacts, sign in to iCloud.

Learn more about using AirDrop to share with people using a Mac with Yosemite.