Photoshop "create PDF presentation" always uses same JPEG compression

Hi,

I am using an Applescript to create a “.pdf” file from multiple “.jpg” images as follows:

-- Capture all "jpg" files on the desktop

tell application "Finder" to set file_list to every file of desktop whose name extension is "jpg"

-- Create a list of aliases to the "jpg" files

set alias_file_list to {}
repeat with f in file_list
	set alias_file_list to alias_file_list & (f as alias)
end repeat

-- Give the output "pdf" file a name including its full path

set pdf_file to (path to desktop as string) & "new_pdf_file.pdf"

-- Create the "pdf" file

tell application "Adobe Photoshop CS" to create PDF presentation from files alias_file_list to file pdf_file with options {encoding:JPEG, JPEG quality:12}

The problem I am encountering is that whether I set JPEG quality to 12 (as in the script above) or to 0 or to any number in between, the “.pdf” file is always created with JPEG quality = 4. I surmise that quality value based on comparing the “.pdf” file size generated by the script to that obtained from directly creating the “.pdf” file in Photoshop (File > Automate > PDF Presentation …).

Does anyone have any suggestions as to how I might get my script to recognize different JPEG quality values?

bmose