How to Distinguish Photoshop from the Real Photo
1 - Cloning of the piece of image is visible
Clone Stamp is a Photoshop tool for cloning. Some parts of the image (i.e. a blank area of the face, free from defects) are copied and transferred to another location (for example, an area with a pimple.) I use the Alt key to determine the source for cloning. To do this, press and hold the Alt key and at the same time use the left mouse button to click on a blank area. Start to paint over the area you want to replace
Spot Healing Brush is the easiest Photoshop tool for cloning. To use this tool, simply slide it over the area you want to change and click once with the left mouse button. Photoshop will do the job, having studied all the information about the pixels around this area, and smoothly integrate this data into the targeted destination.
Healing Brush is similar to the Clone Stamp tool. Alt + left mouse click on a blank space and start painting over the area you want to replace.
2 – Over-Photoshopped (Overdone)
To over-photoshop the photo means that the picture is done unnaturally, too contrasting or there is too much sharpening or noise (dirt, scratches, and small dots around the picture, like dust), etc.
3 - Inaccurate correction
Inaccurate photo correction in Photoshop refers to the appearance of defects in your work (e.g., it is visible how you cut out a flower and when you move it to another location, a sharp transition can be noticed, which looks a little unnatural or it is clear you were too lazy to pay attention to particular object, in order to make it look more realistic).
4 - Effects
Effect is a created illusion of different color tones on a photo (for example, making a photo in warm or cold tones, processed in black & white style, etc.)
5 - Different background + visible clipping + different contrast of photos
This is the same as inaccurate correction of photos or over-photoshopping
6 - Distortion
Distortion of pictures in Photoshop occurs because the inattention of Photoshop designer, when working with transformation. You can easily notice roughness resulting from working with photos that were aimed to get fixed, but it did not work as it should have (for example, while processing the photo of the building you distorted it too much bending it off to the side or to the back).