"Nothing in this film symbolises anything!" Luis Buñuel and painter Salvador Dali once claimed in an attempt to silence the various critical readings of their first and most notorious film, Un Chien Andalou, made back in 1929 when cinema itself was in its infancy. You can certainly appreciate where they were coming from. Constructed largely from from dream imagery, without regard for narrative or character, it remains the purest cinematic expression of the spirit of surrealism, a celluloid representation Andre Breton's definition of the movement as a chance meeting of a sewing-machine and an umbrella on a dissecting table. But given the interpretive aspect of dreams themselves and the heavy Freudianism of much of Dali's own artwork, it is inevitable that the film would be the subject of so much study and that successive generations of writers would attempt to join the Freudian dots. Which has always seemed to me to be missing the point. For many devotees of surrealist cinema it is precisely the disconnected, seemingly random nature of Un Chien Andalou that makes it such a thrilling and revolutionary work. This is the godfather of surrealist cinema, and without it later directors such as Lindsay Anderson, David Lynch and, yes, even Buñuel himself, would not have been able to make their mark in such distinctive fashion.

Un Chien Andalou has, of course, the single most shocking opening sequence in cinema history. As an Argentinean tango dances on the soundtrack, a man – actually Buñuel himself – sharpens a straight razor and steps out onto a balcony to look at the night sky. Once back inside, he holds open the eye of a young girl and, as a cloud passes in front of the moon, slices her eyeball open in horrible, graphic close-up. It remains a seriously jarring image to this day, in part because it's clearly a real eyeball being cut (though that of a dead donkey rather than a live human) and in part because the obvious age of the film makes the inclusion of such a sequence, at least for the uninitiated, completely unthinkable. Imagine what it must have been like to catch it back in 1928. There seems little doubt that this was placed up front with the sole purpose of smacking the audience full in the face, which it does with horrible aplomb. Believe me, there will be few who sit through this moment and just shrug it off, and if you have a thing about eyes, as everyone here at Outsider seems to have, then no matter how many times you see it, you wince.

Nothing in the rest of the film's sixteen minutes is quite as alarming, but the imagery and ideas come thick and fast and make for a film that is more authentically dream-like than anything even Buñuel has made since, and so much of its imagery has passed into film legend that it has become a critical tool in itself. Thus the opening of Sam Fuller's The Big Red One, in which the face of a large wooden statue of Christ crucified is seen to be crawling with ants, was read as surrealistic on its release, reflecting as it does both a sequence in Un Chien Andalou, in which ants emerge from a hole in a character's hand, and the surrealists' antagonistic attitude to religion.* Elsewhere, the connection has been more deliberate, as in David Lynch's Blue Velvet when Jeffrey Beaumont finds a discarded human ear crawling with ants. Dali himself even recalled the open eye-slicing when he created the dream sequence for Hitchcock's Spellbound in 1945, in which large curtains bearing a repeating eye motif are horizontally sliced (along the line of one of the eyes) with oversized scissors.

Un Chien Andalou remains a delicious, dangerous and exciting montage of unsettling dream imagery, a Freudian assault on the senses that repeatedly hints at narratives that never unfold, reflecting the desire of the film-makers to create a work in which no single scene or image can be rationally explained. From its misleadingly playful fairy-tale opening title card and frank celebration of sexual desire to its amusing pot-shots at the church and wonderfully absurdist comic moments, Un Chien Andalou is sixteen minutes of pure surrealist joy. Funny, shocking, richly imaginative and confrontational, this is still THE surrealist film, and possibly the most potent example of avante-garde moving image the cinema has ever seen.

While Un Chien Andalou was a collaborative work between Buñuel and Dali, L'Age D'Or saw Dali taking something of a creative back seat, allowing Buñuel to really find his feet as a director. By now officially a member of the surrealist movement, Buñuel seemed here to be spoiling for a fight. At the sixth public screening he got one when, in a move orchestrated by right-wing agitators, the screen was attacked and the cinema trashed, prompting police intervention and the banning of the film. What on earth could prompt such an extreme reaction? What could be more offensive than the graphic slicing of an eyeball? Well here's a clue: some years later the film was withdrawn from distribution by its own producer, Vicomte de Noailles, following his conversion to Catholicism. Yep, in 1930 Buñuel did the unthinkable – he loaded his cinematic guns and aimed them squarely at what were to become two of his favourite targets, the bourgeoisie and the Catholic church.

As with Un Chien Andalou, L'Age D'Or kicks off in deliberately misleading fashion, with several minutes of nature documentary footage featuring scorpions battling each other and an unfortunate rat, while title cards inform us of their physical make-up and anti-social nature. This seeming misdirection actually lays the foundations for much that follows, a story of a man who rejects all aspects of the society in which he reluctantly moves, and one with a splendid sting in its tale.

The pace is more sedate than that of the earlier film and the narrative more structured, though to suggest that it tells a story in the traditional sense would be way off the mark. Essentially a portrait of the power and frustrations of desire, there are plenty of well-aimed pot-shots taken at the clergy, the family unit and middle class values, many of which are executed with an unflinching directness and wit that still prompts admiration and even out-loud laughter. It also openly celebrates sexual desire and fetishism – itself a subversive move in 1930 – with the almost uncontrollable sexual urges of the two main characters being repeatedly frustrated, twice by the same group of visiting Majorcans. All of this peaks in one of the film's most justifiably famous scenes, where the pair meet in a corner of an ornamental garden and, with engaging clumsiness, attempt unsuccessfully to consummate their passion, one embrace being broken when the male half of this duo becomes fixated on the toes of a white statue that, on his temporary departure, his female companion effectively goes down on. This remains one of the most erotically charged scenes in cinema history, an open celebration of forbidden sexual longing that would no doubt these days have the Daily Mail in an uproar of disgusted disapproval.

As a surrealist film it delivers on all levels, reflecting the movement's revolutionary politics and attitude to organised religion and continuing Un Chien Andalou's dream-like kick against realism. This involves a fair number of delightfully bizarre non sequiturs – the man walking by with a rock on his head (passing a statue of a man with a rock on its head); a title card that announces "Sometimes on Sundays" followed by the explosive destruction of a number of buildings; the man kicking a violin along a street before stamping on it and walking on – but just as many are integrated, however strangely, into the scenes in which they sit. Thus when the leading lady walks into her bedroom and irritatedly shifts a cow from her bed, its absurdity feels only a couple of steps from reality because she behaves as if it were a disobedient dog. Her actions are recognisably normal; it's the choice of animal that throws the scene into the dream world.

Several sequences foreshadow memorable scenes in later Buñuel works, with the maid killed by a kitchen fire yet ignored by the wealthy party-goers having its less drastic equivalent in The Exterminating Angel, while the gamekeeper who shoots dead his young son for playfully snatching his father's tobacco has echoes throughout the director's filmography, from the violent blasting of a butterfly in Diary of a Chambermaid to the priest who calmly uses a shotgun on a man whose last confession he has just taken in The Discreet Charm of the Bourgeoisie.

But it's in the final scene that Buñuel really throws caution to the wind, to the degree that if it were made today it would still cause an uproar. A long textual introduction (based on De Sade's 120 Days of Sodom) outlines the appalling depravities inflicted by "four godless and unprincipled scoundrels" at the Château de Selliny on "eight lovely adolescent girls," culminating in the introduction of their leader, the monstrous Duc de Blangis, who is revealed to be Jesus. Weary from the 120 day long orgy, he still has the energy to return to the Château to finish off a girl who survived the depravities, and in a particularly bizarre gag, gets his beard ripped off. The final image of a crucifix adorned with female scalps, accompanied by jovial music, plays almost like a cheerful declaration of war on Christianity.

If L'Age D'Or lacks the fired-up energy of Un Chien Andalou, it nevertheless remains a marvelous slice of surrealist cinema, brimming with invention and revolutionary daring and a clear pointer to the direction Buñuel's cinema was to take in the years to come. As cinematic companion pieces they are virtually without peer and remain two of the most influential, exciting and enjoyable examples of avante garde cinema at its most ferociously effective.

Oh well. First up, it should be recognised that both films are over seventy years old and and finding a source print that is even close to pristine is a bit of a no-hoper. But given the sort of restoration work done by Eureka on films like M and The Last Laugh, the transfers here leave an lot to be desired.

Un Chien Andalou definitely comes off worst – scratches, dust spots and other film damage are very evident throughout, the contrast range is average and black levels are closer to dark grey. Though much of this is undoubtedly down to the available source print, there has clearly been little attempt to clean this up digitally and the transfer has picked up four small dots that appear to have been actually added to the on-screen distractions (you can tell they are not film damage as they sit solidly throughout, while the film itself is subject to some frame jitter). Perhaps most frustratingly, the extracts of the film included in the documentary on this disk, A Propósito de Buñuel, are noticeably superior in contrast, sharpness and stability. As a silent film with music 'as directed by Luis Buñuel', the only subtitles are those accompanying the title cards, and these are burnt in. The music is as originally recorded for early sound prints, complete with slight distortion and sudden editing jumps.

L'Age D'Or fares a little better, especially on the contrast and black levels (the contrast does vary at times, but this is doubtless due to the the condition of the source print). It still has more than its share of dust spots and film damage, though given that there was an attempt to destroy all prints following its banning this is at least understandable. Again no visible restoration work appears to have been carried out, but some scenes have survived rather well and have a pleasing look to them, despite the damage. The sound shows its age, with music and sound effects sometimes coming across as distorted, but this was one of the first sound films and cannot be expected to be crystal clear. The subtitles here are removable and very clearly done, though have been specifically translated for UK viewers, as can be witnessed in the early scene with the peasant soldiers, one of whom says to the other, "Bollocks."

Though limited in number, the extras on offer here do at first glance appear to be very well focused. Of course, as with other aspects of this box set, it ain't that simple, but one at least is first rate, so I'll save that until last. Most of the extras revolve around Robert Short, author of the books Dada and Surrealism and Surrealist Cinema, and this proves something of a mixed blessing. He certainly knows his subject, but his delivery is as dry and overly analytical as a particularly heavy-going university lecture.

First up is an Introduction by Robert Short, which runs for a most unexpected 25 minutes and consists of a direct-to-camera address in which he discusses the background and production of the two films. Despite his delivery style, this is actually rather interesting, packing quite a bit of information into the running time, and despite my long-standing love of the two films there were a few facts I was unaware of and enjoyed hearing here (Buñuel filling his pocket with stones for the premiere of Un Chien Andalou to throw at the audience in case of a hostile reception is a personal favourite). When I say it's interesting, I mean it's interesting to listen to – visually it's deadly stuff, with Short talking straight to camera, dressed in a shiny black jacket and uninterrupted by stills or film extracts, the mid-shot intermittently (and sometimes jarringly) jumping to a close-up and back in an unsuccessful attempt to liven things up. It's best to ignore the screen and listen while you're reading the included booklet, which really is rather nice and gives plenty of background to the film, including film notes from Buñuel himself.

Short also provides a commentary for each film, though both diverge from the audio commentariy standard in different ways. In Un Chien Andalou, Short examines the notorious opening in detail, and in order for him to do so the sequence is repeated, making this quite possibly the only audio commentary that is longer than the film it accompanies. On L'Age D'Or the reverse is true, with the film edited down to allow Short to concentrate on key sequences only, running for just half the length of the film. As for the content...well therin lies the rub. While a good part of the commentary on L'Age D'Or focuses on the construction of the scenes under examination, the one accompanying Un Chien Andalou over-analyses the film to such a degree that twice I actually lost track of what Short was trying to say and my interest and patience were frequently taxed. Sounding at times as if he's swallowed a whole set of volumes on Freud, Short tones this down a bit on L'Age D'Or, though still kicks off with some thematically baffling musings on the opposing forces of gold and shit.

The final extra, located on the Un Chien Andalou disk, is the best by far, the Spanish/Mexican documentary A Propósito de Buñuel. Rather than an exhaustive study of Buñuel's cinema, it concentrates on Buñuel the man: his childhood in Spain, his religious education, his friendships, his long-standing marriage to Jeanne Rucar, his seemingly puritanical attitude to on-screen sex, his love of martinis and his sense of humour. Of course, his films are dealt with in some detail, but more often than not on a personal and anecdotal level. Running a handsome 98 minutes, this is a thoroughly enjoyable and engaging production, but does have one surprising omission – absolutely none of the participants are identified by name through caption or voice-over, and though you can work who some of them are from what is said or shown, a fair number remain frustratingly anonymous. I'm guessing that all concerned are familiar enough to the programme's original target audience for this not to be an issue for them, but a little help here would have been nice. Shot on video and framed at 1.66:1 (non-anamorphic), the transfer is first-rate, though the quality of included film clips varies wildly. As mentioned before, the clips from Un Chien Andalou are actually superior to the print included on this very disk.

Un Chien Andalou and L'Age D'Or are the two most important works in the history of avant garde cinema and were the founding fathers of surrealist film. Both still have the power, over seventy bloody years later, to shock and astound. What film now will be able to say that so long after it's release?

It's wonderful to see the two films released on DVD, but with the restoration work being carried out on other important works from this period the quality of the transfers here can't help but feel a little disappointing. The inclusion of commentaries is welcome, but ones that actually told you about the making of the films rather than disappearing up an analytical rectum would have been preferable. The inclusion of the documentary, A Propósito de Buñuel, is the real selling point, though I have to take issue with the retail price of of £30, making this two-disk package more expensive than most Criterion sets (and that includes the cost of importing them), which almost always benefit from extensive restoration work and a bucketload of classy extras. Putting the whole set in a fancy, oversized box fails to convince me – it doesn't fit on the shelf with my other disks – and so while the films come wholeheartedly recommended, the DVDs are probably for determined (or rich) devotees only, unless you can find them in a sale.

* I was in an audience at the National Film Theatre some years ago when this very point was put to Fuller, who dismissed it and revealed that the statue was real and the ants were already there and that he had filmed it because it was an interesting image.