Reduce file size when exporting photos.

The options are easy to miss when you are trying to export photos.

In the "File > Export > Export ... photos" dialog click the arrow ^ to the right of "Photo kind: JPEG" to see the options to change the resolution and the compression.

The selector "JPEG Quality" allows you to change the amount of compression, the selector "Size" allows you to change the resolution".

There is no option to select a specific file size, however. You need trial and error to find the best combination of JPEG Quality and Size to get the desired file size.

Basically increase compression or reduce resolution or both. Or additionally use some more compressable codec (.jpg instead .tif, for example).