First, why JPEG 2000? This format is not widely accepted and other users may have trouble opening images.
It is easy to convert .psd to .jpg in the Image Processor accessed either from Bridge of PS.
If it hurts the doctor says don't do it Don't try to change the extension in Photoshop let it use the default. After you run you batch just use an underlying system command to renamed the saved file. Like on a windows system a DOS "rename *.jpf *.jpe" On a mac I think there will be a unix command to rename files using a wildcard character.
I'm not really sure why JPEG 2000, I'm just working part time in the library and that is the format they told me to use.
So if I save them as .jpf and then change them to .jp2, there won't be any difference from converting them directly from .psd to .jp2?
jpeg 2000 is supposedly a lossless format. jpeg is a lossy format, so each time you save it compresses it further and you loose a little bit.
THis is a complicated subject and if interested do a little web search on the 2 formats as well as tiff and png.
To answer the question directly, there is no difference between a file saved as .JPF and renaming it to .JP2. Sometimes JPEG2000 also uses the .JPX extension as well. They are the same.
Curt Y wrote:
jpeg 2000 is supposedly a lossless format.
It can be, depending on options chosen, but that statement is a bit too broad.