Step 1. You can use any photo for this tutorial. If you want to follow me then open this photo.
Step 2. Let's assume we want this photo file size to be less then 20K and that we don't want to manual select the quality of photo.
How can we do this?
Simple. Click on the File - Save for web,
then select Optimize menu and select Optimize to File Size.
Enter the desired file size, in our case 20K choose Auto select GIF/JPEG, and click OK.
Photoshop will then by itself select image format and quality of photo. For our photo we'll get quality 33, JPEG format and file size of 19.85K.
See you!
