Ideally a critic shall express his opinion based on the following considerations,
a. Clarity of thought - A photograph should clearly express the thought / idea /concept behind the photograph as visioned by the Photographer. An aimless image shall go unnoticed / leave a confused impression on the viewers mind.
b. Clarity on the subject - A photograph sould clearly identify the main subject around which the photograph is framed. A large number of components fighting for attention will only ruin the image.
c. Harmony of elements - All elements in the image shall be harmonic to the nature of the subject and not contradict to it / make it seem unusual. A photograph showing a bird on tree perch shall appear more effective than the one sitting on an electric pole/ window grill. Like wise a bird eating fruits on trees shall appear more pleasant that a caged bird.
d. Clarity on mood - The light setting shall have to convey the mood of the image. A woman with Diwali lamps in hand will appear more natural if mild warm light is made to fall on her from the same angle as that of the lights, whereas using a bare flash would only ruin the image.
e. Active subjects - The image appears more impactful if the subjects are involved in an activity of natural instinct. Photograph of a person indulged in cutting wood / smoking / moulding a clay pot / pulling a cart would be more meaningful than an image of person just watching TV or a selfie taken at food court of a mall.