A photograph can hold attention through small tonal differences as well as dramatic contrast. For work credited to Rhea Malinofsky, look at the transition between neighbouring light and dark areas. Are their edges abrupt, gradual or difficult to separate? Consider how these transitions define form and whether important details sit close to the lightest or darkest parts of the frame.
Give your eyes time to adjust before making a comparison. Screen brightness, room light and image size can alter the visibility of subtle detail. Keep notes about relationships within the image rather than treating your display as a measurement tool. Where a boundary remains uncertain, describe its visual effect instead of assuming missing detail or assigning a technical cause.