According to Don McCullin in his autobiography "Unreasonable Behaviour", director Michelangelo Antonioni was unhappy with the color of the grass in Maryon Park. He had it sprayed green so he could re-shoot the scene.
As a way of bypassing the Production Code (i.e. censors), MGM created "Premiere Productions". This was a dummy company which had no agreement or affiliation with the Production Code and, therefore, did not have to adhere to its standards. MGM did not have to cut the full frontal nudity or other sexually explicit scenes and maintained all rights to the film. When the film opened to rave reviews and excellent box office, this defeat was considered the final blow for the Production Code's credibility and was replaced with a ratings system less than two years later.
Thomas' workhorse camera was the then innovative Nikon F, the world's first 35mm SLR with full coupling of shutter and aperture with its exposure meter. Even though the particular model had been around since 1959, the glamorous publicity it received in the movie generated an unprecedented enthusiasm among camera buffs, professionals and amateurs alike.
Michelangelo Antonioni offered little in the way of insight into his intentions with the film, and was always clear that meaning wasn't meant to be spelled out. "By developing with enlargers...things emerge that we probably don't see with the naked eye....The photographer in Blow-Up, who is not a philosopher, wants to see things closer up. But it so happens that, by enlarging too far, the object itself decomposes and disappears. Hence there's a moment in which we grasp reality, but then the moment passes. This was in part the meaning of Blow-Up."
To Vanessa Redgrave, this was a film that was as much about listening as it was seeing. "...Michelangelo's ear, not for dialogue but for the sounds of nature and normally inanimate objects," she said, "was as subtle as his eye."
Michelangelo Antonioni felt that the film marked a "radical" departure from his previous films. "In my other films, I have tried to probe the relationship between one person and another--most often, their love relationship, the fragility of their feelings, and so on. But in this film, none of these themes matters. Here, the relationship is between an individual and reality--those things that are around him. There are no love stories in this film, even though we see relations between men and women. The experience of the protagonist is not a sentimental nor an amorous one but rather, one regarding his relationship with the world, with the things he finds in front of him. He is a photographer. One day, he photographs two people in a park, an element of reality that appears real. And it is. But reality has a quality of freedom about it that is hard to explain. This film, perhaps, is like Zen; the moment you explain it, you betray it. I mean, a film you can explain in words, is not a real film."
Even though the film was set in London, Michelangelo Antonioni was adamant that the story wasn't necessarily about London. "I was hoping," he explained, "that no one in seeing the finished film would say: Blow-Up is a typically British film. At the same time, I was hoping that no one would define it exclusively as an Italian film."
During film, David Hemmings was annoyed to see that Michelangelo Antonioni was shaking his head back and forth in the gesture that he had interpreted as negative during his audition process. However, he soon realized that the gesture was simply a tic and had no negative meaning at all. "Once the mystery was solved," he said, "I was prepared to love him; and I never told him about the week of hell he'd put me through as a result of his affliction."
While there was always a screenplay to work from, Michelangelo Antonioni allowed himself plenty of freedom for the creative process to be organic. "I depart from the script constantly," he said in a 1969 interview. "I may film scenes I had no intention of filming; things suggest themselves on location, and we improvise. I try not to think about it too much. Then, in the cutting room, I take the film and start to put it together, and only then do I begin to get an idea of what it is about."
Vanessa Redgrave offered her take on the film in her autobiography. "Blow-Up was about the unity and difference of essence and phenomena, the conflict between what is, objectively, and what is seen, heard, or grasped by the individual."
Vanessa Redgrave had to work double duty while filming her role. She would shoot with Michelangelo Antonioni during the day in London while at the same time starring every night, plus two matinees a week, in the title role of The Prime of Miss Jean Brodie on stage. Despite the rough schedule, however, Redgrave found it very rewarding to work with Antonioni. "With Michelangelo the camera angle, its movement, the frame, their colour, position, and movement, whether human or inanimate, told his story," she said in her 1991 autobiography. "The dialogue was of no great significance, or certainly of secondary importance. Trained as a dancer, I was able to appreciate this. I learned to look sharply and precisely at the shapes and colours around me. Exact positions, angles of the body, the head and shoulders, exact tempo of movement, were vital to him. I had never encountered such an eye in the cinema. In English and American films, colours and shapes were part of the decoration, appropriate, but only as background to the action. In Michelangelo's films they were the action."
Michelangelo Antonioni said that he was aiming for a sense of "cold, calculated sensuality." He tried to help capture that feeling by using what he called "enhanced" or the "hardest and most aggressive" of colors. It was part of his vision to "recreate reality in an abstract form. I wanted to question 'the reality of our experience,'" he said. "This is an essential point in the visual aspect of the film, considering that one of its main themes is to see or not to see the correct value of things."
To loosen things up, David Hemmings decided to start the production with a bang. Literally. "In those days, when the money involved in making a picture was a lot less than it is now, it wasn't an uncommon opening ritual to test the mettle of a director [on a new production] by winding him up a little. In this case, we thought it would be a good wheeze to blow up a beautiful Mulliner Park Ward convertible Rolls-Royce. In one of the earliest shots, my character, Thomas...drives the Rolls away from a dosshouse where he's spent the night, snapping the run-down inmates. Thinking fast and with most of the crew ready to help, we suspended a pair of large steel plates under the engine and loaded them with nuts and bolts and any other oily metal objects we could find that looked like bits of engine. We also wired in under the bonnet a small, harmless bomb that would explode with a loud bang and a dense cloud of smoke." Having carefully planned the prank with the prop master who had a "wicked" sense of humour, Hemmings prepared for the first shot with the cameras rolling. "I drove the car round the corner into view and Props gave me the nod," he recalled. "I pulled a lever that had been rigged up for me under the dashboard and, instantly, a muffled explosion echoed off the walls of the drab brick buildings, immediately followed by a metallic clatter of detritus tumbling onto tarmac and a plume of blue-grey smoke spewing from under the bonnet of the vehicle. I snapped off the motor and came to a screeching halt." "An ominous silence followed the bang and the last rattle of metal. In the mirror I saw what looked like an entire engine scattered along the street behind me. It was so convincing, I almost believed the car had blown up." "Pierre Rouve, the producer, stood rigid at the roadside, as if paralyzed by cardiac arrest," Hemmings continued. "He had bought the car for the production from Jimmy Savile and I guess he was planning to keep it for himself afterwards. Now it looked like a write-off. The Maestro [Antonioni] himself barely winced. With a few tidy strides, he walked up to the sick-looking Roller, beckoning a spark to open the bonnet. He peered inside. Everyone on the set was laughing." "Antonioni slowly straightened his back and looked up at me where I still sat, pale and shamefaced, in the driver's seat. There was a shrewd, angry glint in his eye. 'Che cazzo fai?' he rasped icily. 'Stronzo! You have to learn now, David, this is not a picnic. We are here to work!' He knew perfectly well we'd been trying to wind him up, but now, a little late and with a nasty hollowness in my gut, I realized he was a very serious man indeed, entirely his own master, accountable to no one. And one of the greatest directors I ever worked for."
According to David Hemmings, Michelangelo Antonioni and Director of Photography Carlo Di Palma argued constantly. "There was also a sense that Di Palma was pretender to the Maestro's throne, Carlo's Iago to Antonioni's Othello, which may have added to the palpable tension between them," he said. "He certainly had no qualms about challenging his boss. Antonioni, being the Maestro, never let him have his way completely but, in the end result, it was clear that their explosive rapport produced astonishing images. In achieving this, though, there were these moments of quite alarming aggression, which never perhaps reached their natural conclusion, inasmuch as the two men never hit each other, but a great deal of shouting, arm waving and surrogate kicking went on - fireplaces, ladders, tables, anything. Kick, kick, kick."
Michelangelo Antonioni shot some of the scenes in the real-life studio of famed London photographer John Cowan, one of the main figures who had influenced the character of Thomas in the script. Cowan rented out his space to Antonioni and acted as an advisor to him on certain details to help provide an authenticity to the world of high fashion photography.
According to one of the models who appeared in the film, Jill Kennington, the famous scene between Thomas and real-life fashion icon Veruschka as he whips her into a sensual frenzy while snapping her picture was quite authentic. "[That] scene for Blow-Up was pure Cowan," she told Vanity Fair in 2011. "Antonioni must have seen him working--I never saw anyone else take pictures quite that way. The shooting on the floor downwards, completely fluid, unhindered by tripods, etc., was typical Cowan."
David Hemmings was amazed at Michelangelo Antonioni's energy and stamina throughout the production. "I was an energetic 25-year-old - probably more so than most - and I was fascinated by the way Antonioni, at 54, could operate around the clock and still sustain a momentum he needed to get him through the production," he said. "It seemed that, however late he'd gone to bed the night before, he appeared on the set each morning as bright-eyed as a bantam cock, and just as well-groomed...For a man of his age, he was impressively eager for new experiences. I think perhaps he was a little in thrall to the idea of 'swinging London' and even once shooting had started, he spent a great deal of time hanging around in search of oscillation, often with photographers and models. Perhaps he considered it all research, but in his quest he raved ceaselessly, night after night in clubs and discotheques, in the company of the new goddesses of the fashion world, with his fierce eyes shining intensely in the dark, grave face as he drank grappa till his ears bubbled and tried to extract every last ounce from the swinging city - a man from Rome, a modern Bellini, determined to leave his mark in the middle of the liberated new world."
MGM was prepared to release the film when it was finished. However, it was hindered by the refusal of the Production Code office to issue its seal of approval. The office had a particular objection to the scene in which Thomas has a playful Ménage à trois with two giggling young aspiring models that featured uninhibited nudity and sexuality.