Most people cannot tell if their photographs are over exposed or under exposed. Sometimes it takes a photographer years of experience to tell whether their photographs are correctly exposed.
However, half the times the exposure is correct but the condition which the photographs were taken were awful and can be avoided altogether. And if a lot of people use software like the Adobe Lightroom or Photoshop to post process their photos, without using a calibrated monitor!
One should always remember that it is a good practice to get your exposure correct, or close to correct, even if you post process all your photographs. This is especially so for over exposed photographs as the information is completely lost making post processing correction almost impossible and unnatural. It also saves you plenty of time.
So how do you tell? Before we begin, this section will only apply to determining exposures using the camera’s LCD screen playback. And also, I will focus on portrait photograph for now as it is the most common to find exposure problems in amateurs. It is not easy to look at someone’s portrait and tell if the exposure is wrong because our eyes and brain will compensate for the exposure and tell you that there is nothing wrong with the photograph!
You must always remember, your SUBJECT is your priority! When faced with difficult lighting conditions always make sure your subject is correctly exposed. (However, in more advance photography where heavy post processing is used, the brightest area of the scene is used as the exposure yardstick and a slightly under exposed subject is acceptable.)When accessing the exposure, always look at your subject first. I know some people use the sky, or the building in the background as their exposure yardstick (which is WRONG)!
Usually the first thing I will do is to look at the skin for “hot spots”. Skin “Hot spots” are areas that are shiny and is caused by over exposure. Next, is to look at the dark part of your subject’s clothing, preferably black, like the black ribbons on Tina’s dress on the left. If you see the black in your subject clothing is dark blue/brown or washed out black, it is a tell-tale sign of over exposed photographs. Also, another way is to look at the shadow area within the hair. If you can see the details in the hair shadow area, it is most likely the photograph is over exposed.
The first thing I will look at is the eyes of my subject, particularly the sclera (eye white). An under exposed photograph will have a darker grey rather than light grey. Under exposure can also be determined by looking at shadow area but generally the subject exposure is priority. Under exposed photographs will not have much details in the shadow or the details will not be prominent. Details like hair stands will not be highly visible.
However, under exposed photographs can be easily be corrected these days by software.