... To truly manipulate an image, you are distorting or changing the image to be something different from what you originally saw.
To merely "perfect" the image, you are attempting to make the necessary adjustments to best reflect what you DID see that prompted you to take the photograph in the first place...
In a (rare) agreement with Jack, may I suggest the National Geographic's stance
on the subject, and in particular (emphases mine):"... Please do not digitally enhance or alter your photographs (beyond the basics needed to achieve realistic color balance and sharpness). If you have digitally added or removed anything, please don't submit the shot. We look at every photo to see if it's authentic, and if we find that yours is in any way deceptive, we'll disqualify it..."
I am sure this is further going to inflame the debate, particularly among the pedants on the forum with philosophical inclinations (or sheepskins), into the direction of "what the definition of 'is' is", i.e., the meaning behind the words "enhance", "alter", "authentic", "deceptive", etc. To them, I offer my favorite quote, by the supreme authority on the subject (paraphrased): "Like love and pornography, hard to define, but you'll know it when you see it."
P.S. The first person to divert the discussion toward the placement of punctuation marks above shall forever be exiled to Dante's fifth circle