There are three tonal ranges in a picture, which are generally assimilated to make a photograph. The low-key and high-key are product of the same picture, exposed differently-e.g. expose normally as meter says - they cover 99% of the picture taken unintentionally again exposing correctly having all tones as seen in the picture........again for example we are not viewing or expecting the picture in dark tones or light tones....if it is, it may be discarded. and may be treated as underexposed or overexposed.....You are well aware of the darker toned pictures of old persona. Thus the LOWKEY or HIGHKEY are best suited subjectwise as in portraiture and other subjects too. They are the result of thoughtfullness of b&w days, when subjectwise we printed in soft grade of paper for low key photographs and in normal paper for high-key effect.
It was maximum tried in portraits or still life photography, where the photographer had control over the lowkey effect or the highkey effect pix while printing in the enlarger. ....HIGHKEY portraits are ethereal and PREDOMINNTLY WHILE WITH OCCASIONAL OF BLACK IN IT, BUT NOT WASHED OUT WHITES AS WHEN OVEREXPOSING A PIC AS ABOVE. LIGHT TONAL RANGE IS MAINTAINED WITH DETAILS in the subject. The high key pix display mood of joy, levity,ecstacy and purity suited to children, women.......in comparison to lowkey portraits, which portray dull, morose mood suited to aged and old people.....
...............................high key....predominantly white having details in white areas and some of black in dull tone...............Lowkey predominantly dark toned still visitability of details in darker areas
welcome Vimal.......The photo is overexposed, thus losing the details of the subject almost in totaliity