You could morph it into another galaxy and it wouldn't change.
Bottom line is that you're providing a service. Unless there's a contractual transfer of copyright, nothing changes.
There are a multitude of service labs, all operate under similar terms and conditions and often perform 'photoshop services' similar to the one you're describing - for an hourly fee (more often than not). There's no transfer of copyright either legally or procedurally unless there's a specific, and probably written, agreement to the contrary.
The only potential exception, would be if you did it 'pro bono' with the written or implicit agreement that the (c) was now yours - the consideration being transfer of (c) - and even then I suspect you'd need a written agreement for it to stand up in court.
All this stuff about 'service provides', 'hourly fees', and 'pro bono' work are irrelevant (at least in the US). Copyright law doesn't care about any of that — it protects original, creative works. Full stop.
An examples from a different media might be easier to understand: If I write a novel and I hire someone to turn that novel into a screenplay for a movie, the screenplay is its own creative, derivative work and establishes a copyright owned by the screenwriter. As the novelist, I can't take that screenplay and turn it into a movie without a license from the screenwriter. The screenwriter also needs a license from me because the right to create derivative works of the novel in the first place is owned by me (baring fair use arguments involving transformative work). Here's almost everything you need to know about derivative works:
http://copyright.gov/circs/circ14.pdf. You will find no mention services, or hourly fees.
Additionally, as Bart and Schewe point out, a work needs to meet a threshold of originality to qualify for copyright protection. That's the test, not whether someone is a service provider but whether the derivative work is sufficiently original and the difference between it an the original work are more than trivial. Copyright protects original expression, not effort or expense exerted. If, as the creator of a derivative work, you haven't added anything creative to the original, regardless of how much work you did, you don't establish a new copyright for yourself. This is why a press operator doesn't create a new copyright when running a printing press.
A good example of how the courts deal with this is available in Ets-Hokin v. Skyy Spirits Inc. Ets-Hokin, a photographer, created product shots of Skyy's vodka bottle and there was a disagreement about whether the photographs established their own copyright or were unoriginal copies of a bottle. The case had some interesting twists and turns and illustrates how difficult this question can be to answer. The district court found that the photos where not original works, and on appeal the court found the bottle couldn't be copyrighted in the first place because you can't copyright utilitarian objects. (
https://www.law.cornell.edu/copyright/cases/225_f3d_1068.htm )
So the question you need to ask about the retouched photos is: does the retouching add sufficiently new original ideas and is the retouched photo more than trivially different from the original. If the answer to those questions is yes, then you have a new derivative work to which you own the copyright. But it doesn't transfer any rights of the original owner's creative work over to you, so it may be of limited use other than preventing others from exploiting your creativity.