Cézanne’s breakthrough came from his gradual understanding of his own focal points. Every artist usually starts to focus from about 1 ft away from their faces outwards. Cézanne seemed to notice that inside this field, vision becomes much more unstable due to the phenomena known as “saccading”, the tiny movements of the eyes as they switch between focal points. This meant that the fixing of a contour becomes difficult as your bifocal lenses hop back and forth seeking their equilibrium. In projecting this situation outwards he noticed that everything in the wider field of vision was equally unstable - if you look intently.
Remember, that artists since the birth of perspective had aspired to the singularity of focus that the camera had eventually presented us with, mechanically (as if this device confirmed what had been sought all along and was indeed how we see). It may have taken the camera’s influence to instil a challenge in him. He was part of the Impressionist wave of artists in his formative years and they had already taken on board the consequences of the camera on composition and sight , yet their resultant fleeting instability of picture making was still ‘filmic’ at heart. For all their radical improvisations, Impressionist pictorial logic actually reinforces the single viewpoint of the camera- it just adds a sense movement, but it is still a single point movement. This is why we see so much blurring of features in the peripheral sections of a figure painting or generality of rendering of the landscape in Impressionist paintings. Cézanne clearly wanted something more - he said so , a permanence, a solidity, a surety. Ultimately a truth, one based upon the integrity of response to the purely un-choreographed visual experience of looking at the world and then synthesising this looking into the concrete actualities of paint on canvas.
All western painting up to this point had sought to fix forms in space. For the first time through Cézanne, space became “space-time”. Painting now moved into the fourth dimension and space itself became mutable, fluid and ultimately, unstable. This instability became a strength, though. Now the very perception of movement felt haptic rather than depicted. A mannerist painting deliberately amplifies the twisting contortions of a figure in space for dramatic effect, installing an almost theatrical sense of movement. Cézanne created a more peculiar but more meaningful feeling of movement in closely hued inter-relational passages of colour which describe form as it is truly apprehended when scrutinised. Put it simply, he analysed the experience of looking not just the thing looked at, in doing so, he saw how reality loses its assumed solidity and certainty. The expressive irony being this instability of perception led to such a powerful certainty of pictorial reality. Truth is not easy on the eye.