The excellent Exhibition on Screen series ventures into new territory with Phil Grabsky's David Hockney At the Royal Academy of Arts, as not only does this typically illuminating study feature a living artist for the first time, but it also covers the works presented in two separate Royal Academy shows, `A Bigger Picture' from 2012 and `82 Portraits and One Still-Life' from 2016. Moreover, for once, Grabsky is merely the latest in a long line of film-makers to pay homage to David Hockney, who has made frequent appearances on screen since he was seen working in his studio in James Scott's 1966 short, Love's Presentation.

In addition to being the focus of feature documentaries like Jack Hazan's A Bigger Splash (1973), Philip Haas's A Day on the Grand Canal With the Emperor of China (1988), Billy Pappas's Waiting for Hockney (2008) and Bruno Wollheim's David Hockney: A Bigger Picture (2009), the Bradford-born octogenarian has also twice collaborated with Randall Wright on David Hockney: Secret Knowledge (2003) and Hockney (2014). But, as is often the case with Exhibition on Screen, the emphasis is placed more on the work than the life and times of the artist himself.

Following a brief introduction from Royal Academy Artistic Director Tim Marlow, critics Martin Gayford and Jonathan Jones put David Hockney's achievement into context, as they describe his `eyeballing' approach to producing figurative art, his interest in the history of painting and his willingness to experiment with differing artforms. Over `Grand Canyon With Ledge' (1986), `A Closer Grand Canyon' (1998) and Mulholland Drive: The Road to the Studio (1980), Jones commends Hockney's honesty and the sense of curiosity that has kept him searching for new ways to depict the world around him.

After Senior Curator Edith Devaney explains how the exhibition of Yorkshire landscapes came about and we see `Bigger Trees Near Warter' (2007), Grabsky cuts to Marlow interviewing the artist at the Royal Academy in 2012. Hockney reveals that `Fields, Eccleshill' and `Bolton Junction, Eccleshill' (both 1956) were painted with cheap materials when he was still at art school and he admits that he was consciously trying to avoid emulating LS Lowry. As a young man, however, he had been keen to see the wider world and `Flight Into Italy: A Swiss Landscape' (1962) captured his journey through the Alps after he had accepted a lift from a stranger and had been unable to see the stunning scenery because he had been sitting in the windowless back of a Mini van.

Marlow asks if this painting was a deliberate rebellion against the existing vogue for abstraction and Hockney agrees that he felt the reaction against representational art in the postwar period was unjustified. He has always been happy to record the landscape he witnessed in places like Egypt and California in such pictures as `Rocky Mountains and Tired Indians' (1965) and `Nichols Canyon' (c.1980). Consequently, he has never had a problem switching between landscapes and portraits.

Close-ups follow of `The Road to York Through Siedmere' and `Salts Mill, Saltaire, Yorkshire' (both 1997) to examine Hockney's draughtsmanship and use of colour before Marlow asks about the six paintings that were produced for ailing collector Jonathan Silver, a fellow Bradfordian who had persuaded Hockney to take another look at his home county. Knowing that his friend was dying, Hockney had made a prolonged stay and, while driving through the countryside, he had been inspired to paint `Garrowby Hill' (1998). Following the death of his 99 year-old mother and the loss of a close friend in LA, Hockney went to stay with his older sister, Margaret, and felt drawn back to the landscape to produce items like `Midsummer, East Yorkshire' (2004), which was originally made up of 36 watercolours before being rendered in oils.

He also produced six-panel pieces like `A Closer Winter Tunnel, February-March'. `Woldgate Woods III, 20 and 21 May', `Woldgate Woods, 26, 27 and 30 July', `Woldgate Woods, 6 and 9 November' and `Woldgate Woods, 21, 22 and 23 November' (all 2006), which consciously focused on the centre of the image rather than the edges. Hockney explains how he hit upon the structure of these pieces because he couldn't get any larger canvases up the stairs to his rented studio in Bridlington. He also notes how he prefers to paint en plein air because the light intrigues him. But Hockney often reproduces his outdoor watercolours in oils in the studio and he describes how items like `The Big Hawthorn' (2008) and `Winter Timber' (2009) were based as much on memory as in situ sketches and recalls Pierre Bonnard's famous line about painting outside being so confusing because there is always too much information to take in.

Over a shot of `Felled Trees on Woldgate' (2008), Hockney dubs this method of working memory editing, while he goes on to the gallery floor to point out the influence of individual prints on a giant picture that dominates an end wall in the 32-canvas collection entitled `The Arrival of Spring in Woldgate, East Yorkshire, 2011 (twenty eleven)'. He tells Marlow that he prefers painting in spring and autumn, as they are active seasons in Nature. But he decided to begin this sequence with winter impressions in `4 January 2011', `8 January 2011' and `19 February 2011' to show how the view changes with time into '14 April 2011', '12 May 2011' and '31 May 2011'.

In order to work at the necessary speed, Hockney began sketching on an iPad and he discusses the pros and cons of working with new technology. He also reveals how he decided to exhibit so many contrasting views in a single room because it was impossible to look at more than one image at a time on the tablet screen. In declaring this enterprise to be a partial success, Jonathan Jones nevertheless commends Hockney's readiness to experiment in returning to the scene of his youth and painting the likes of `Three Trees Near Thixendale, Summer 2007', `Three Trees Near Thixendale, Winter 2007' and`Three Trees Near Thixendale, Autumn 2008' from Nature in the manner of John Constable and Claude Monet.

This refusal to rest on his laurels also prompted Hockney to make films like `May 12th 2011, Rudston to Kilham, 5pm', `May 11th 2011, Woldgate Woods, 1:45pm'. `Nov. 6th, Dec. 3rd, The Tunnel, 2pm and 1pm', `June 2nd, Nov. 26th 2010, Woldgate Woods, 7:30am and 11:30am' and `November 26th 2011, Woldgate Woods, 9:30am', which all sprawl thrillingly in slow pans over 18 linked screens.

Marlow asks Hockney about embracing technology and he confesses to using it only in so far as it helps him make pictures. He had been invited to the launch of Photo Shop on the strength of `Pearblossom Highway, 11-18 April, 1986 #1' and had predicted the end of chemical photography as the norm. But he is also fascinated by how China has moved away from the multiple perspectives of scroll art to embrace the single-lens technique of film and television, while Western artists have started to experiment more with variations on the scroll theme. This is why he produced his multi-screen moving landscapes and yet he still ensured that they bore the influence of Constable, JMW Turner and Rembrandt Van Rijn, as he is always conscious of the British landscape tradition.

As the 2012 interview ends, Hockney concedes that he is discovering new things about an exhibition that took him four years to assemble. It represents a phenomenal burst of creative activity that captures moments of sadness and celebration. But it also reaffirms that the 75 year-old (as he was) had no intention of boring himself, even if others considered him dull.

Following a last tour of the landscape show, the scene shifts to July 2016, as Marlow explains that Hockney returned to Los Angeles to embark upon a series of portraits. Painted in 22 hours over three days in the Academy 4:3 ration, each picture depicts its subject in full figure seated in a chair. Each canvas bears individual scrutiny, but this stands as a single work of art that reflects Hockney withdrawing from the expanses of his landscapes to more intimate images of his friends and colleagues.

Edith Devaney recalls how the project sprang from `J-P Gonçalves de Lima, 11th, 12th 13th July 2013', while Hockney (speaking in LA in September 2015) explains that it took him a time to generate enthusiasm for this RA commission and it was only when he decided to place his model on a platform for `Bing McGilvray, 23rd, 24th, 25th August 2013' and decided to include the feet in each picture that he hit upon a working method. He began quickly in producing `Richard Sassin, 9th, 10th, 11th September 2013', `Douglas Roberts, 17th, 18th, 19th September 2013' and `Greg Rose, 20th, 21st, 22nd September 2013', and felt he had the right time frame for each study, as he didn't want to detain his models for too long.

By the time he painted `Joan Agajanian Quinn, 16th, 17th, 18th October 2013' and `Kevin Druez, 28th, 29th, 30th October 2013', Hockney felt he was in the swing and, eventually, Devaney went to his LA studio to visit him. He shows her `Margaret Hockney, 14th, 15th, 16th August 2015' and Devaney notes how relaxed his sister seems, as he reveals that he made a preliminary sketch in charcoal directly on to the canvas in around 45 minutes before starting to use colour. Devaney explains how studio assistant Jean-Pierre Gonçalves de Lima (seen in `J-P Gonçalves de Lima, 15th, 16th 17th January 2016') not only prepares Hockney's paints, but also takes photographs of works in progress, so that we can see how pictures like `Edith Devaney, 11th, 12th, 13th February 2016' evolved.

As we see snapshots of Hockney working with Barry Humphries, he explains that he enjoyed having people over and getting to know them, as he rarely goes out any more. Moreover, as Devaney notes over `Chloe McHugh, 9th, 10th, 11th November 2013' and `Dr Leon Banks, 12th, 13th, 15th November 2013', these images of little-known figures build into a who's who of Hockney's acquaintances while also holding up a mirror to us all. Some of the subjects were children whom Hockney had watched grow up and, as we see `Jack Perlman, 17th, 18th February 2014' and `Holden Schmidt, 27th, 28th, 29th July 2015', he reveals that the latter was an 11 year-old who deeply resented being made to sit still for an extended period and Hockney is amused by the look of deep suspicion in his eyes.

Devaney reveals that Hockney is hard of hearing and fed off being in a relaxed atmosphere while painting `David Stoltz, 16th, 17th, 19th November 2013', `Oliver Goulds. 25th, 26th, 27th November 2013'. `Gregory Evans, 1st, 2nd, 3rd December 2013' and `Stephanie Barron, 7th, 8th, 9th January 2014'. Indeed, he was so laid back about the sittings that he allowed each model to pose themselves in the chair and went with their first instincts. Hockney also highlights the contrasting approaches to attire in pictures like `Dagny Corcoran, 15th, 16th, 17th January 2014' and `Jonathan Wilkinson, 19th, 20th, 21st January 2014', as the women tended to dress up more than the men.

He also comments on how men's fashions have changed (and not necessarily for the better) during his lifetime and draws attention to the way that footwear reflects personality in portraits like `Avner Chaim, 27th, 28th, 29th January 2014', `Douglas Baxter, 8th, 9th, 10th February 2014', `Ivan Schreiber, 24th, 25th, 26th February 2014' and `Jackson McCoy, 4th, 5th, 6th April 2014'. As the images were not commissioned by the sitter, Hockney had a freedom to paint what he saw and Devaney reveals that he did two pictures of her, which, he felt, reflected different aspects of her personality. However, he also had to record whatever the sitter was wearing and he contrasts the Breton fisherman's jersey sported by Devaney with the red taffeta skirt in `Rita Pynoos, 1st, 2nd March 2014', which gave him much more trouble.

The sole still-life in the exhibition is `Fruit on a Bench, 6th, 7th, 8th March 2014' and Devaney explains that it was something of a running joke that it would be included in the show. Yet, when it came to finalising the pictures, they both agreed that it was a portrait of sorts and deserved its place in the line-up.

Back at the RA in June 2016, Hockney and Marlow sit down to discuss the thinking behind the series. Hockney reveals that a close friend had died in tragic circumstances shortly after he had returned to California from Yorkshire and the image of Jean-Pierre with his head in his hands became akin to a self-portrait, as they shared the same sense of sorrow. But, as he warmed to his task, the pictures came to reflect a more positive mood and Hockney agrees that working has a cathartic effect.

Employing a slow-drying acrylic paint, Hockney was able to set his own pace and he used the photos that Jean-Pierre took during the painting of each picture to plan how to proceed on the second and third days of each sitting. As we look at `Barry Humphries, 26th, 27th, 28th March 2015', Jonathan Jones suggests that the likenesses aren't always great. But he also posits that Hockney was drawing on the influence of Henri Matisse to convey the emotional power of colour and he is very much taken by the jolt of life that each painting provides.

Marlow also highlights the one-to-one engagement that each image demands, as he ponders whether portraits of old friends, such as `Gregory Evans, 1st, 2nd, 3rd December 2013', `Martin Gayford, 4th, 5th, 6th December 2013', `Benedikt Taschen, 9th, 10th, 11th December 2013' and `John Baldessari, 13th, 16th December 2013', were conscious efforts on Hockney's part to find something new in the familiar. Marlow even asserts that the exhibition as a whole represents a deconstruction of the process of painting, as while some of the individual brushstrokes may not be fully resolved, the overall effect is daringly novel.

Gayford compares Hockney and Lucien Freud's approaches to portrait painting and notes that the `20-hour take' technique meant that Hockney needed to concentrate and had little time for nattering. Marlow asks why he imposed such a limit on himself and Hockney alludes to the fact that Vincent Van Gogh rarely spent more than three days on his portraits (or more than five days on a landscape). He also reveals that he always told the sitter which part of their anatomy he was working on at any particular time to keep them engaged in the process and to ensure that they kept as still as possible. Moreover, he explains that he only ever worked when the subject was present, as he wanted to paint from life not memory or photographs, as the likeness mattered less than capturing the truth of the encounter.

As Hockney wanders around the galleries with Marlow, he reveals that a handful of sitters were painted on two or three occasions, while the only person who had refused to look directly at him during their sessions missed the cut. He plans to do more, as he concurs with Rembrandt that every portrait contains elements of self-portraiture. But he also avers that it took him some time to get to grips with the rationale and method of the series and it was only when he produced `Rufus Hale, 23rd, 24th, 25th November 2015' that he had a full understanding of the project as a whole. This boy was one of the youngest subjects, while his pursuit of youth also prompted Hockney to break the rules of the task with the dual portrait of the strapping siblings in `Augustus and Perry Barringer, 16th, 17th June 2014'. But, even though, Leon Banks and Rita Pynoos were in their nineties, Hockney didn't set out to cover the Seven Ages of Man.

By selecting a neutral blue-green contrast between the curtain and carpet used as a backdrop, Hockney strove to emphasise the unity and individuality of each sitter in images like `Ayn Grinstein, 10th, 11th, 12th March 2014', `Maurice Payne, 30th May, 1st, 2nd June 2014' and `Julie Green, 11th, 12th, 13th January 2015'. He also banished thoughts of how the viewer might react to the pictures in order to retain the intimacy and intensity of the sitting and it was only after he had finished around 40 canvases that he started to wonder how they would be exhibited.

Keen to continue the series, as people always make the most interesting subjects, Hockney feels under no pressure to conform or rebel, as he remains a naturally curious person and is forever getting new ideas for material and approaches. He is also content to reflect on his past and has enjoyed working on a retrospective volume for Taschen. As we rove the gallery to alight on pictures like David Juda, 22nd, 23rd, 25th March 2015' and `Celia Birtwell, 31st August, 1st, 2nd September 2015', Devaney comments on the empathetic intelligence of the portraits and the democratic nature of the project. She also suggests that it's obvious that they are later works and contrast starkly with items like `American Collectors (Fred & Maria Weisman)' (1968), which took months to complete. What no one sees fit to mention, however, is the fact that the sitters are predominantly white and affluent, with a rare exception being `Earl Simms, 29th February, 1st, 2nd March 2016', which almost feels like an afterthought.

Jones and Gayford briefly ponder his legacy before Hockney confides that people keep urging him to stop smoking. But he doesn't want to think about the effects on his body when he lights a cigarette to contemplate a canvas. He wants to make the right choice and jokes that there can be nothing more in life than painting landscapes, portraits and still-lifes.

Clearly comfortable on camera, Hockney always makes for genial company. But he has developed the happy knack of being able to talk a good deal without giving too much a way. Thus, he spends much of these interviews side-stepping Marlow's often stuffily earnest questions. Yet, while we learn frustratingly little about his techniques and artistic preoccupations, we get to hear plenty of amusing anecdotes and asides that reveal more about Hockney the man than he perhaps intended.

As always, Grabsky and his team of cinematographers make a splendid job of capturing the essence of the artworks to the jazzy accompaniment of Dmitri Tchamouroff's score. But there is little question that the landscapes trump the portraits in terms of visual impact and theoretical intrigue and some may find time hanging heavily after the often enchanting and enlightening tour of Yorkshire. This is partly due to the overlap between Devaney and Marlow's line of inquiry when chatting to Hockney about the portraits. But the latter exchanges feel like something off a TV arts show and, thus, lack the sense of cinematic moment that has been a key component of Exhibition on Screen's success. Moreover, in understandably wanting to make the most of his access to Hockney, Grabsky neglects the expert critical insight to which we have become accustomed and it's a shame there aren't a few more objective observers to debate the doubts lurking behind Jonathan Jones's occasionally faint praise.