Affordances are both objective and subjective; or rather, those categories don't made sense for affordances.
From Gibson's *The Ecological Approach to Visual Perception*, p. 129:
> An important fact about the affordances of the environment is that they are in a sense objective, real, and physical, unlike values and meanings, which are often supposed to be subjective, phenomenal, and mental. But, actually, an affordance is neither an objective property nor a subjective property; or it is both if you like. An affordance cuts across the dichotomy of subjective-objective and helps us to understand its inadequacy. [...] An affordance points both ways, to the environment and to the observer.