I have the latest version of Lightroom, 3.4.1.
Lately, I have been using the Lens Correction feature more and more.
I have 3 Nikon lenses and one Tamron lens.
I have noticed that when I check the box to Enable Profile Corrections, it automatically finds the correction if it is one of the 3 Nikon lenses.
However, if the image was taken using the Tamron lens (28 - 300 mm), LR does not automatically find the profile. The message is "Unable to locate a matching profile automatically." When I enter "Tamron" in the Lens Profile Make, then LR automatically finds this particular lens.
Is there a reason LR finds the profile fully automatically for the Nikon lenses but does not do so for the Tamron lens?
I did what I think you are suggesting, and this is what happened.
I went to a picture taken with that Tamron lens. I clicked on "Enable Profile Corrections." At that point, "None" showed in the Make field as well as in the Model and Profile fields.
I then selected "Tamron" to be in the Make field. Both the Model and Profile fields then were populated (and, the Model field was populated with the correct 28 -300 mm lens).
Then under "Setup," I did select "Save New Lens Profile Defaults."
I went to the next picture and again selected "Enable Profile Corrections." This time, the Make, Model, and Profile fields were properly populated because that next picture was taken with that 28 - 300 mm Tamron lens.
However, I skipped a few pictures ahead, to a shot taken with a Nikon lens, and this time when I selected "Enable Profile Corrections," instead of putting the Nikon lens information in those fields, it put the Tamron 28 - 300 mm lens information in those fields.
It appears as if perhaps I will have to "Save New Lens Profile Defaults" every time I go to a new photo which uses a different lens, unless I am not understanding what you have suggested to do.