I stored the grabbed exifs in a text file.
path to desktop as text
set theFile to result & "theExifs.txt"
set theDatas to read file theFile
set theKeys to {"FileName", "FileModifyDate", "YCbCrPositioning", "MeteringMode"}
set theValues to {}
repeat with aKey in theKeys
my decoupe(theDatas, aKey)
paragraph 1 of item 2 of result
my decoupe(result, ": ")
item 2 of result
set end of theValues to result
end repeat
my recolle(theValues, return)
#=====
on decoupe(t, d)
local oTIDs, l
set {oTIDs, AppleScript's text item delimiters} to {AppleScript's text item delimiters, d}
set l to text items of t
set AppleScript's text item delimiters to oTIDs
return l
end decoupe
#=====
on recolle(l, d)
local oTIDs, t
set {oTIDs, AppleScript's text item delimiters} to {AppleScript's text item delimiters, d}
set t to "" & l
set AppleScript's text item delimiters to oTIDs
return t
end recolle
#=====
Extracting the four values with that is quite instantaneous.