We can use the word "see" in two different ways: we can refer straightforwardly to things that we see, or we can "notice an aspect": I can also see something as something. Wittgenstein gives a picture that can be seen either as a duck or a rabbit. We can see it either as a duck or as a rabbit, but not as both simultaneously. If I have only ever seen it as a rabbit, I do not say, "I am seeing it as a picture-rabbit," but simply, "this is a picture-rabbit." Nonetheless, someone else might well say of me, "he is seeing it as a picture-rabbit."
Our temptation is to say that there is an immediate perception that consists of colors and shapes in my visual field, and then also an interpretation of that perception, where I see those colors and shapes as a particular object. But I do not say of a fork, "I am seeing this as a fork," except in unusual circumstances. And when of the duck-rabbit I say, "I see a rabbit," I am reporting, not interpreting, my perception. My perceptions—what I see—are of things and people, not of colors and shapes.
Seeing is too complicated to be reduced to visual sense impressions. The element of familiarity, for instance, helps us to recognize a portrait that is the right way up far more easily than one that is upside down.
If "what I see" is just an inner picture, I see the same thing when seeing the rabbit or the duck aspect of the duck-rabbit. In this case a picture of "what I see" is an incomplete description because it does not fully make clear what I am seeing. Is it a different visual impression when I see the duck and when I see the rabbit? There is no inner picture to justify expressions of what we see or how we see it: there is simply how we describe it. The concept we bring to a picture forces itself upon us without interpretation. We could call it the attitude with which we look at the picture.
The experience of seeing certain objects as certain other things often requires a kind of knowledge or "mastery of a technique" in order to experience them as such. For instance, I must be familiar with ducks and rabbits to see those two aspects of the duck-rabbit. What we can do, what we know, often determine the kinds of experience we have: to talk about a hesitant posture or a plaintive melody presupposes some experience of certain emotions and their common expressions. That one fails to experience a certain aspect is not a defect in one's eyesight.
We can be struck by an aspect of a picture for a certain length of time, and then no longer be struck by it. This does not mean that our visual experience changes, or even that our thoughts change. What dawns on me when I see an aspect of a picture is not so much something in the picture itself, but in its relationship to other pictures.