I meant by "ethical background and standard of editing images" is edited by someone else to alter the image beyond the intent of the owner of a photograph.
When an image is created the photographer is almost always considered the owner of the image. The exceptions would be if the photographer created the image for another entity (individual or corporation) under a "work for hire" agreement or under a contract specifically stating that the resulting images are owned by a party other than the photographer.
For anyone other than the owner of the image to edit it usually requires permission from the owner of the image. To edit and use an image without the permission of the owner is usually considered unethical and is illegal under civil or even criminal law in many jurisdictions.
There are exceptions, particularly for two sub-categories, satire and fair use, of what are known as "derivative works" where an image or parts of an image are used to create another work. The legal 'standard" for what is a legitimate derivative work and what is not can vary greatly from one country to the next and even from one judicial district to the next. Particularly with civil cases, precedents set by different courts operating in different districts that fall under the same statutory and tort laws in the United States can indicate what appears to be opposing interpretations of the same laws.
In this article that appeared in the Suffolk University Law Review (vol XLIV:605) regarding a specific case involving the use of photographs of products, a lot of the basics about copyright and derivative works are discussed throughout the article with a plethora of footnotes that reference other resources and related case studies. This statement on page 610 is particularly enlightening about the lack of consistency from one court to the next in how they interpret and render binding legal opinions in this area.
Due partly to the mechanical nature of photography, courts have generally
struggled with defining the originality standard for photographs and in
particular with contextualizing photographs within the framework of derivative
works.28 Although specifically protected by statute, photography has proven to be a problematic medium for copyright law due to diverging opinions regarding the applicable level of creative distance necessary for a finding of originality, in tandem with the unresolved issue as to whether photographs are derivative works or simply depictions of the underlying materials.29 Despite the overall lack of consensus, copyright is consistently denied in cases of “slavish copying,” with courts exhibiting a distinct pattern of favoring departures from convention over technical proficiency.30
When the above quote uses the phrase "diverging opinions" it is a reference to "legal opinions": written explanations by a judge or panel of judges that accompanies a court order or ruling in a case, laying out the reasoning and legal principles for the ruling.
This article from the American Society of Media Photographers succinctly explains three copyright issues that may affect a derivative work:
- Original rights: The owner of the original work has control over how that work is used in derivatives. You must obtain permission of the owner of the original work and follow any limitations placed on the original work by that work's owner. Allowable exceptions, such as parody or fair use, can often be challenged by the owner of the original work and lead to court cases which must establish whether the derivative work falls under such exceptions or not.
- New copyright: Copyright protection of the derivative work is only applicable to the new elements introduced in the derivative work. It does not grant the owner of the derivative work any rights to the original work referenced in the derivative work.
- Disclosure: When registering the copyright of the derivative work, you must disclose the ancestry of your derivative work. That is, you must disclose the sources upon which your derivative work is based.
Notice that in this Brown University Library Article Images: Finding and Using, there are pretty succinct answers for the use of established works of art in their original form. But the point regarding derivative works begins with the sentence, "Not an easy question to answer."
Beyond the law, the entire question of ethics regarding derivative works has even less of any real defined standard than the laws and opinions rendered about them do. As this PetaPixel article, Imitation vs. Copying in Photography: The Issue of Derivative Works, and the ensuing comments point out: You can't argue in court using ethical, moral, or 'common' sense. You can only argue based on the law and previous rulings that have set precedents as to how those laws should be interpreted.
This FAQ from Lumen regarding derivative works.
"Copyright in Derivative Works and Compilations", a circular from the U.S. Copyright Office.
The Public Domain vs. the Museum: The Limits of Copyright and Reproductions of Two-dimensional Works of Art
Derivative Works at Wikimedia Commons.
Legal and Ethical Issues with Intellectual Property