The problem is the interpretation of what we bring to the photograph and that falls along the lines of a continuum in which each of us has to determine what is acceptable and what isn't. Continuums make for problems in which solutions become elusive. For instance, what constitutes "tall?" If we lined up every one in the world by height, and we chose 100 people to independently draw the line between two people to demarcate what they consider short and tall, we would end up with 100 different solutions, some of them thousands or even 100's of thousands of people apart. And it would probably be difficult to convince a seven foot basketball player that a six foot six inch guy is anything but short.
The same is true for what is acceptable and what isn't acceptable as far as alteration of a photograph. The continuum seems to fall in two categories. 1) what we do in the camera and 2) what we do digitally on the computer.
For instance, film does not necessarily record color the way the human eye sees color. (Some blue flowers reflect a spectrum of light that we see very very differently from film. Some of these flowers turn pink, unless you use flash as your main light source.) Velvia, or any super saturated film, renders a scene in a range of colors that may be significantly different than what we see; some call Velvia "neon" and find its colors objectionable. Some films render greens differently than others; some are balanced towards the "cool" end of the spectrum and some towards the "warm" end of the spectrum. Even Black and White papers range from "warm" to "cool."
Then we add telephoto lenses that not only bring the subject "closer," but also compresses perspective unnaturally making mountain ranges, that are miles apart, stack up like waves on the ocean. Wideangles expand the perspective and may even warp vertical straight lines if the camera is tilted. Large apertures decrease the depth-of-field unnaturally (at least in some instances) while small apertures increase depth-of-field unnaturally (at least in some instances). Then we add polarizing filters to "darken" the sky in color photography, or a red filter to "blacken" the sky in black and white.
In the end, some of the scenes we photograph are, in essence, altered enough that it would be impossible to see that scene through the human eye exactly the way it was captured on film. Yet, if it is done in the camera, I think we generally accept this as being OK.
The digital continuum proves more controversial. For instance, where would each of us draw the line in the following continuum:
1. Scanning a photo and not doing anything to it regardless of what it looks like.
2. Changing an under or overexposed photo to a "normal" range.
3. Changing the contrast and color to what we remember.
4. Changing the contrast and color to what we would like.
5. Reinforcing the catchlight in the eye of an elk.
6. Adding a catch light in the eye of an elk
7. Removing a twig from in front of the deer's eyes.
8. Removing the unslightly powerline from a New England church scene.
9. Moving one of the Pyramids of Giza so it fits better as a backdrop to a cigarette ad.
10. Moving one of the Pyramids of Giza so it fits better on the cover of National Geographic.
I've heard arguments that nothing digital should ever be done to a photo, but I'm not sure that is a good answer. One could state it is OK to alter a digital image to match the contrast and color range of the original photo, but the original photo is, in essence an intrepretation of what was seen in the first place. Then one could make an argument that we should be able to modify the photo to what we remember (the sky was darker blue, the flower was more red), but that runs the risk of relying on how good our memory is.
I've also heard vigorous arguments that if it doesn't materially change the "message" of the photo or portrays something that couldn't otherwise happen, it's OK to modify it. So for instance, if that reed falls over the bittern nest, maybe we should just digitally edit it out since its removal doesn't materially change the message of the photograph or portray something unnatural. (My solution was to physically move the reed, but at what potential expense to the bird (disturbance) and to me (possibly not getting any photos by frightening the bird away?))
Interestingly enough context in which the photo comes into play is probably important as well. We could probably care less if a cigarette advertisement digitally moves one of the Giza pyramids a bit to make for a better composition, but when National Geographic actually did so, they were excoriated for perfectly understandable reasons; we hold the National Geographic to different standards than RJ Reynolds advertising department.
Lastly (hopefully), it is probably OK for someone to edit out a low hanging branch intruding into a photo of the local parishoners of the church for use in their 100 year anniversary advertisment, but it wouldn't be acceptable to edit out a powerline in front of the New England church and use it on a calendar because doing so creates a scene that doesn't exist. That is I couldn't go there and duplicate that scene myself by standing in the same place and I wouldn't be happy if I drove to Maine thinking that this seaside town was more picturesque than what it really is. Again context rears its head.
In the end, its up to each of us to define what we mean by acceptable along that continuum and while the discussion is pertinenta and should be discussed, it is not a problem that will be easily solved. It is also one that is a very divisive issue.
I agree though that if an image is digitally altered, that that information is pertinent and should be noted. I just don't know at what point along the continuum it should be noted that would be acceptable to everyone. Personally, I don't rely on my memory and so adjust contrast and color based on the actual photograph.
Got pretty long-winded here. Congratulations for getting to the end.