Can humans ever directly see a photon?

Yes. In fact, photons are the only things that humans can directly see. A photon is a bit of light. Human eyes are specifically designed to detect light. This happens when a photon enters the eye and is absorbed by one of the rod or cone cells that cover the retina on the inner back surface of the eye. When you look at a chair, you are not actually seeing a chair. You are seeing a bunch of photons that have reflected off of the chair. In the process of reflecting off of the chair, these photons have been arranged in a pattern that resembles the chair. When the photons strike your retina, your cone and rod cells detect this pattern and send it to your brain. In this way, your brain thinks it’s looking at a chair when it’s really looking at a bunch of photons arranged in a chair pattern.Your eyes can see bunches of photons, but can they see a single, isolated photon? Each rod cell in your eye is indeed capable of detecting a single, isolated photon. However, the neural circuitry in your eye only passes a signal along to the brain if several photons are detected at about the same time in neighboring rod cells. Therefore, even though your eye is capable of detecting a single, isolated photon, your brain is not capable of perceiving it. If it could, an isolated photon would just look like a brief flash of brightness at a single point. We know this because a sensitive camera sensor is indeed able to detect and process an isolated photon, and the photon just looks like a brief flash of brightness at a single point.
A photon has several properties, and each of these properties carries information about the source that created the photon or the last object that interacted with the photon. The basic properties of a photon that carry information are color (i.e. frequency), spin (i.e. polarization), location, direction of propagation, and wave phase. There are also many other properties of a photon; such as energy, wavelength, momentum, and wavenumber; but these are all dependent on the frequency and therefore do not carry any extra information.