Photoshops can lead people to believe in a reality that does not actually exist . Nature photography that we often see in glossy books can be stunning, but it can also be fake, courtesy of digital technologies . Nature is beautiful,and needs no human intelligence to improve on what was created. If you add something that wasn’t there in the original scene, you’ve crossed the line into fiction.
If you are trying to portray a picture as truthful, then it is unethical to photoshop. If your purpose was to create fiction,then you may go ahead and add, substract, manipulate the colours, and destroy the original. Once you photoshop a picture, it is no longer an original creation,but a manufactured fake. The real beauty is out there in nature and any representation of that beauty in a photograph is only a poor imitation of the real thing. To photoshop, is making reality unreal and fantasy real,in a bastardised photograph.