Everyone thinks they know the impressionists. Manet; Monet — café scenes or water lilies — Degas; Renoir — dancing girls or smiling girls. It’s all the same really.

But, Pissarro: The Father of Impressionism at The Ashmolean looks further back, when the movement was but a glint in its earliest salon-avoiding practitioner’s eye.

The exhibition opens with paintings that are almost indistinguishable in their commitment to realism: country scenes by Jean-Baptiste-Camille Corot sit opposite those by Charles-François Daubigny. In this context, Barges on the Seine (1863) looks less like the first shot of an artistic revolution than it does another day painting, in the immortal words of Bryan Ferry, the same old scene.

But, before any exhibition-goer begins to question the integrity of a curator who claims Pissarro to be the “father of impressionism”, suddenly visible daubs of paint and light and colour burst into the picture. The Village Screened by Trees (1869) and Countryside near Louveciennes (1870) have the subtle hints of what is to come: blue and orange skies, loose greens and browns in the foreground, and people only conjured up by a flick of the wrist detailing their clothes.

But it is in Pissarro’s paintings of people that the true skill of his early years lies. The squat, somewhat ugly form of Cézanne is brilliant not for its aesthetic beauty — Pissarro was no Gainsborough, painting his subject in the best possible light and most decadent clothes — but for its genre-stretching possibilities. Cézanne sits in front of an impossible background of a caricature of Adolphe Thiers (the then leader of the French government) on L’Eclipse newspaper, and a figure of the fellow painter Gustav Corbet. Cézanne’s face seems to echo and reflect Courbet’s, but Pissarro’s rendering of the texture of his skin and beard is so much more real, more tangible. There is a clear difference between the subject of the portrait and his background.

In the exhibition, much is made of the radicalism of this portrait. Its collection of scenes and objects which matter to the sitter it has more than a hint of Van Gogh’s later chair portraits, and was evidently influenced by Édouard Manet’s 1868 portrait of Émile Zola.

It is a hallmark of exhibitions at the Ashmolean to make brilliant use of the works they hold on paper

But there is also something deeply familiar about it: in including political references and signs of Cezanne’s work as a painter, there is something of Hans Holbein’s The Ambassadors (1533). How different is this figure of Cezanne to the young men standing beside the proofs of their scientific and diplomatic education? This does not dim Pissarro’s achievement or talent — the unsigned, perhaps unfinished work captures something of the fellow artists intensity — but rather sees his portraiture taking the tropes and models of the genre, and bursting them open to his own ends.

His portrait of his daughter, Minette Holding a Doll (1874) is famous for its implied tragedy: her hair is cropped short as the result of a fever, and her curiously large, oval-shaped eyes give the rest of her face more than a slight pallid appearance. The painting is again, unfinished — she died not too long afterward. But it is just one of the many works Pissarro made of Minette and the rest of his family.

It is a hallmark of exhibitions at the Ashmolean to make brilliant use of the works they have on paper. The gallery’s Western Art Print Room is one of the best of its kind, due to the holdings of the Bodleian, gifts from John Ruskin, and — particularly brilliantly for this exhibition — the Pissarro family collection. These works on paper are fragile and rarely exhibited, but here is a chance to see tentative, tender, and intimate watercolours and charcoal drawings of the Pissarro children alongside the far more famous paintings. It is not just Camille’s works that are present, either. One of the exhibition’s gems is a pen-and-ink sketch The Impressionists Picnic (c.1900) by Pissarro’s second son Georges: Cezanne continues to paint, whilst Pissarro, Gaugin, and Guillaumin enjoy a hearty picnic. Here is painting, and eating, en plein air.

Works from all the group Georges’ picnic-scene depicts are included in the exhibition. Paul Gachet, a doctor in Auvers-sur-Oise, encouraged the “Pontoise” school of impressionists to take up etching, and even bought a printing press for this express purpose. Early etched works by Pissarro sit alongside those by Guillaumin, Cezanne, and Gachet himself — each marking their work with an individual little drawing. Here, in works so rarely shown to the public, and even more rarely shown together, is the delicate, papery-trail of an artistic movement beginning.

The exhibition ends with the big block-busters everyone expects in impressionist exhibition: happy peasant workers picking apples or peas in sun-dappled fields (Pissarro, Apple Picking, 1887-8), darkly-lit, fiery fair-grounds (Hayet, Fairground at Night, 1888-9) and glassy, silvery channels in front of impossibly creamy skies (Seurat, The Channel at Gravelines, 1890).

But, after leaving, I felt a palpable sense that the most impressive works, or, at the very least, the ones I was most impressed by — perhaps solely because I haven’t seen them endlessly re-produced on posters, mugs, and tea-towels — were the less-famous prints, watercolours, and drawings.

One particularly captivating corner of the exhibition shows a series of wood-engravings and watercolours Pissarro worked on with his son, Lucien. In one watercolour, Camille’s notes are visible — “3^e femme, coiffe blanche” and “2^e coiffe Rouge et jaune” — all in a classic French cursive. Look at your Seurat spots and Gaugin still-lifes all you like, I’m going to carry on deciphering tricky handwriting. Long live the Ashmolean print room.

Pissarro: Father of Impressionism is at The Ashmolean until 12 June 2022.