Question: How do I Save a Photoshop File for an Older Version?
In the discussion forum, Jesperc asks: "Does anyone know how to save a file in Photoshop CS2, so that it can be open in Photoshop 6?" My answer relates to backward compatibility when opening files from any newer version of Photoshop using any older version of Photoshop.
Answer: There is an option in Photoshop preferences called "Maximize PSD File Compatibility" (under menu Edit > Preferences > File Handling). You will want to make sure this is set to "Always" or "Ask." Turning this option on, however, does result in larger file sizes. If you only need this feature occasionally, you can set it to "Ask" and Photoshop will ask you if you want to maximize compatibility every time you save a file. When this option is used, the layers are saved along with a flattened composite of the image.
Still, when you open a newer version file in older version, the new features of Photoshop will not carry over when the file is opened in an older version that did not contain these features. If the file is edited and saved from the older version, the unsupported features are discarded.
For instance, there are some new blending modes that were added since Photoshop 6 came out. If you used any of these in your file and then edit it in the older version, the image may look different. Other new features like smart objects, certain effect layers, layer sets or groups, layer comps, etc. won't carry over. You might want to make a duplicate of your file and simplify it as much as possible before trying to open it in an older version.
The same applies when opening Photoshop files in other non-Adobe software that reads PSD files.