1. Copy the images you want resized, and put them into 2 new folders: 1 for vertical images and 1 for horizontal images. Make sure to copy the images, as the copies will be permanently resized.
2. Start Photoshop.
4. Open just one of the horizontal (wide) images you want to resize.
7. Hit Record and make sure you don’t do anything outside these instructions, or it’ll get recorded too.
Now, start at #4 but open a vertical/tall photo from that folder. The changes you make are in naming the action like in Step 6, but this time it is resize 600px tall and in step 9, first change the resolution to 72, then change the Height to 600.
Go to File>Automate
In this Batch window, select the action you want to use. Go down to Source, make sure Folder is selected and click the Choose Button. Find the Horizontal folder you made, then go to destination, make sure Folder is selected, then click the Choose button and select the folder you want the resized images to go in (a 3rd new folder is a good idea).
Click ok and wait a really long time while Photoshop runs the processes. When that batch is done, do the same thing, but choose the tall photo action, and the Vertical folder.
Once all the images are resized, you can add them all to the same folder and rename it whatever you want, like “thompson family portraits” or whatever.