Let's look at the photo shown above. Here is a magnified view of the face at 400%. As you can see, there is almost no detail in the image despite the fact at lower magnification, there appears to be some detail.
You should also notice all the "artifacts" in the image. That is the general term for all the dust, scratches, and defects. What if I increase the contrast and the amount of detail using Adobe Lightroom? Here is the modified version.
The photo looks like it contains more detail, but the artifacts are also more prominent. This photo demonstrates an important point, you are, in a sense, stuck with the resolution, detail and content of the original. For me, it is a toss up as to whether the unretouched scan or the altered one is the better of the two images. What if I take out all the artifacts? Here is a preliminary attempt.
Here is my question. Is the mark on her mouth a defect or a scar? Here is the same image after working on it for a while at 400% magnification.
Here is the entire photo again with the alterations.
Now, you can compare the image here with the image at the beginning of this article before I made any changes. Can you see what was done to the image? Would it matter to you to know that this person had a prominent scar on her face? Would you post this altered photo without disclosing the original or at least, putting on a notice that the image had been altered from the original? What if I confined my changes to removing the scratches on the image of the dress?
Depending on the amount of time I wanted to spend, I could "fix" all the defects in the image. Here is a very interesting in-depth discussion of some of the legal issues involved in altering photos.
Parry, Zachariah B., Digital Manipulation and Photographic Evidence: Defrauding the Courts One Thousand Words at a Time, Journal of Law, Technology and Policy, Vol. 2009, p. 175.
Altering historical photographs cuts us loose from reality. Granted any photo is a representation of "reality" at the time the image was made, but once made, the image, in a sense, becomes the only observable form of that incipient reality. We can justify all sorts of changes to the "original" for a whole list of reasons, but the don't we have an overriding interest in having available the most authentic, unchanged historical evidence possible?
That is my ultimate question and unfortunately, I have no easy or comprehensive answer.
Here are the previous posts in this series: