Today we take it for granted that we can make a 2D image of anything our eyes can see at a touch of a button, with a camera, a copier or a computer. However this is relatively recent, until the 20th century making images was a skilled business, exclusively the trade of the artist. This lecture is about how technology automated the process of making images, and how the art world coped with this enormous change. Nobody now considers it cheating to photograph a scene instead of painting it. However, art is a strange business, and painting from a photo is definitely seen by some as cheating.

Even a pencil can `cheat'. In fact, the idea for this lecture was partly inspired by Paul Spooner, an artist who only half jokingly accused me of cheating while watching me draw a cartoon. I start with a pencil, scrubbing about, gradually deciding where the lines should be, what looks right. (I never went to art school, I'm an engineer by training, and I can only draw in this one style which evolved over 14 years doing a weekly cartoon strip for the Observer (called The Rudiments of Wisdom) so I remain a sort of primitive. Eventually I go over the lines I like with a pen, and finally rub out the pencil. Paul had previously admired my drawings, assuming I had some unerring ability to get my pen in the right place every time - but this use of the pencil was `cheating', it was almost copying, not drawing.

Historically, though, artists have done much more cheating than simply using pencils. The renaissance artists were so keen to make their paintings look `real' they used all sorts of tricks. Realising that medieval paintings had rather strange perspectives, they drew elaborate geometrical constructions to make sure they got it right. But they went further, inventing a whole series of grids, screens and sights to `improve' their work. I had been drawing for several years before I found myself holding out my thumb at arms length to compare the relative sizes of things - a simple version of these renaissance drawing aids which I had assumed was simply an artists pose, but it's actually very useful.

None of these things were considered cheating because the role of the artist at the time was a sort of skilled tradesman. Lots of skills were involved, there were no art shops to buy materials, the artist had to make everything. The word art meant skill, artists even had to grind their own pigments to make their paints. This was a slow process, they often spent longer grinding than painting. As a skilled tradesman the artist had practical functions like painting the portraits and possessions of the rich, decorating important buildings, and doing religious paintings which were effectively adverts for the church. They even did pornography - double sided paintings with a respectable scene on one side and nudes on the other. They were also court jesters (Michaelangelo made snowmen for the Medicis) and enterprenneurs (Leonardo advertised his services as a designer of siege and war engines).

None of the geometry, the contraptions, the assistants, etc were seen as cheating, merely `tricks of the trade'. In fact they were often closely guarded secrets - the mysteries handed down from one generation to the next. Because of this secrecy, few artists revealled their techniques in print and many of their techniques have been lost, though I was delighted to find that an artist called Cennini even used a version of my drawing trick `Draw your figure with charcoal and then fix it with ink'.

By the 18th century other `tricks' were in common use, the simplest just used shadows. The miniature silhouette reached its peak in popularity at the end of the century. All that was needed was a sort of shadow pantograph.

More sophisticated was the Camera Obscura. A pinhole creates a faint image of a brightly lit scene which can be seen in a dark room or tent. The effect is very magical, the whole world reduced to a simple flat image, ready to draw round and colour in. These took a while to become popular, partly because an artist called Torrentius had been accused of witchcraft for using one. By the 18th century though they were in general use, Canaletto even had a special blacked out camera obscura carriage, which he would park in front of a view. By the end of the century lenses had also become more common. These made the obscura image much brighter than the pinhole, but had to be a particular distance from the paper to be in focus. This explains the iris on a modern camera - the smaller the hole light is allowed to pass through, the more the lens starts to behave like a pinhole, getting less bright but increasing its depth of field. You can actually improve your eyesight with pinholes (correcting your lenses by increasing their depth of field), try looking through a hole in a water biscuit, its handy to know they make good specs.

Back to the camera obscura. Here there are some records of protests at their use, one critic writing they were `opugnant to the truth of a drawing', but still surprisingly few. This was perhaps because painting and sculpture were now called `The Polite Arts'. The technical skills of the artist were considered increasingly less important than the theories and concepts behind the image. This idea was eagerly promoted by artists like Joshua Reynolds in the 18th century, though it goes back to the ancient Romans, (Pliny believed that thinking and debating were far superior to actually doing or making anything). Amongst other things, Reynolds founded the Royal Academy to establish his cult of learning and classical illusion and his belief in the noble dignity of the artist (and that good taste was a matter of right and wrong). I'd always suspected Reynold's was a terrible snob looking at his portraits. One art historian went so far as to say `no English artist of his eminence is so unnattractive a personality'.

The idea that art was intellectual was helpful to artists wishing to better their position in society, and charge more for their work. Painting became a respectable hobby for the rich. This was partly made possible by the appearance of ready made paints and brushes - avoiding the need for the art of making them. The little known American artist, John Rand, probably had more effect on painting in the 19th century than anybody else - he invented the metal paint tube. Easily available artists materials probably resulted in more bad art, spending days grinding your pigments focuses concentration when finally applying them and certainly reduces your output (it would be hard to imagine Jackson Pollock sploshing about in quite such a carefree way).

Anyway, while the august Royal Academicians were busying discussing the intellectual content of their art, other less dignified people were experimenting with `drawing by light'. The Camera Obscura produced a flat illuminated image, all that was needed to record the image was a chemical that would change colour with light. (This not an uncommon phenomenon - dyes fade if left long enough in light and varnishes darken). It was known that silver compounds darken with light, but though an image could be made, it had two problems; first it wasn't sensitive enough to capture the dim image produced by a camera obscura, and secondly the image gradually disappeared when left in the light (there was no way to `fix' it).

People tried iron compounds, which turn blue with a long exposure to bright light. Never sensitive enough to capture the dim image inside a camera, this was later used for printing from negatives (the prints were called cyanotypes). By 1900 it had found another use, becoming the standard method of copying drawings - the blueprint.

First to create an image from the dim camera obscura was the printer Joseph Niepce. Joseph could not draw well and had relied on his son Isidore to draw the printing plates, but in 1814, Isidore left to join the army. Joseph started experimenting producing images with the sun. He spread his plates with a layer of a type of bitumen. This did not change colour but hardened in the light and after exposure, the parts which were still soft could be washed away. The exposure took all day and the images were hardly recognisable. At the time, one artist wrote `who will ever be interested in the invention of Mr Niepce, the crushing superiority of painting is obvious to every eye'.

Niepce eventually formed a partnership with a landscape artist called Daguerre. In 1839 they published details of a completely different technique, producing beautiful images of an amalgam of mercury on silver. (Reproductions of Daguerreotypes give no idea of their metallic quality). One reason I started writing this talk was as an excuse to try and make a Daguerreotype, but I ran out of time. Anyway, Daguerre immediately sent one of his spectacular images to the Louvre, but it was returned as being of no interest. Rejected as art, his images did quickly become commercially successful, fashionable as portraits and (in Paris) as pornography. The reason pornography went no further than Paris was probably just that it seemed so shocking - real naked women not just paintings.

Initially much less promising were the attempts of the English mathematician, scientist, tourist Henry Fox Talbot. Unaware of anyone else's work, Talbot was struggling to draw a scene on lake Como when he realised he might be able to cheat using `chemical' drawing (Most of the early photographic experimenters were artists). Messing about with silver chemicals, Talbot eventually discovered that, with a few additions, he could produce a `latent' image with a relatively short exposure. The image remained invisible until put in another chemical, the developer.

The popularity of Daguerreotypes in the 1840s encouraged others to improve on Talbots `calotype' process, particularly a sculptor called Scott Archer who replaced the paper base with collodion, a transparent gel made of the explosive guncotton. This became the basis of victorian wet plate photography. The glass plate, with a coating of collodion and pottasium iodide, had to be sensitised by dipping in silver nitrate just before the photo was taken. It then had to be developed immediately. The negative image this produced, which had to be sandwiched with another bit of sensitised paper and exposed again to make a print, was at first seen as over complicated, but its advantages were gradually realised, particularly the ability to make multiple copies.

It was still slow. The first photos of busy streets made them appear empty - people in the street never stayed still long enough to be recorded. The first person to be photographed in focus was a dead man. Even when the process was improved people had to stay motionless for up to a minute holding a fixed expression. Many rested their arm on their chin to keep their head still, others used an `appui tete', an iron frame to rest against the back of the head. No wonder we think of the Victorians as so stiff and formal.

The art world continued as if nothing had changed. Personally I  love many of the victorian paintings that lurk in provincial city art galleries. Individual artists did start to be influenced by photographs. The pre-raphaelites started painting some parts in focus and some out of focus. When you think about it your eyes don't actually see the world in this way, but photos do. Other artists, as film speed improved, became interested in movement - Degas dancers are said to have been inspired by Muybridges photos. However, photography was generally considered crude and intellectually inferior craft, the refuge of failed painters with little talent.

Ignored by the fine art establishment, victorian photographers definitely started to regard their work as art. One photo in particular `The two ways of life' made in 1857 by Rejlander caused great debate. Built up of 17 separate photos crudely stuck together, it showed good life and bad life (bad looking far more enjoyable). Much of the fuss was about the nudity - which appeared to confirm that the ignoble was just too tempting. The photographic society of Scotland only agreed to show it as long as the offending side was covered up. Supporters of the work felt it improved on nature, because it only selected the best bits of each component and elevated the photograph to something that looked like a painting. But others regarded it as cheating at photography.

Much more influential than any of the photographic artists was the American George Eastman, the founder of Kodak. Eastman first perfected dry glass plates (which avoided the need to carry around wet chemicals). He then went on to develop the first film on a flexible backing that came in a roll. By 1888 he was selling a cheap camera with a 100 exposure roll of film inside. When the film was finished, the camera was returned to the factory where it was refilled and the exposed film printed. For the first time people didn't need to carry a tent full of equipment. For the first time making images needed no skill - anyone could cheat at art, `snapping' their friends, their holidays, their pets. Photograph became a popular hobby and much more than that.

It is sometimes said that photography caused the death of painting. Photography is quick, cheap, and this century has generally recorded events and people more vividly and accessibly than painting. In an age of mass production the renaissance role of an artist as a skilled practical tradesman seemed increasingly irrelevant. Art was forced to reinvent itself, becoming `Modern Art'. The first move away from victorian realism came at the end of the 19th century with the gradual acceptance of the impressionists. Though the paintings now look calm and light they were first regarded as shocking. Though mostly painted in Paris, they were first recognised in the less stuffy atmosphere of America (in the 1880s), from where their influence gradually spread. 

Quite unlikely modern artists continued to be influenced by photography. The spindly lines in Klee's paintings were inspired by one of my heros, Mr Gilbreth. Gilbreth tied light bulbs to people and took long exposures to analyse their movement. This was the basis of many time and motions studies aimed at improving productivity, but became quite widespread.

For a long time, painting still had one big advantage over photography - colour. Its easy to forget just how long colour photography took to be perfected, the first true three colour `Kodachrome' film didn't become available until 1935. The principle of colour photography is simple - take three black and white photos of the same scene through red, green and blue filters and project them, superimposed, through the same coloured filters. The scientist Maxwell demonstrated this with magic lanterns in the 1860s. Trying to combine it all on a single roll of film was far less straightforward -it still seems a bit like alchemy to me. Despite Kodak's large research laboratories, the idea for the successful kodachrome film came from two New York musicians, Leopold Mann and Leopold Godowsky, who are said to have timed their dark room operations by whistling classical music. Their film only had an ASA of 5, nearly ten times slower than today's colour films, and required 28 stages to process.

It was first introduced in perforated strips 35mm wide, so the same film could be used for movies as well as still photos, and was responsible for the rise of the relatively compact 35mm camera. By this time photography was well established and had confidentally become art in itself.

Though colour photography in some ways provided greater competition for painting, by the 1930s the idea `Modern Art', with its confusing number of different styles or `isms', had been completely accepted. Cubism, abstraction, surrealism, post-impressionism, futurism, pop, expressionism, post painterly abstraction, super realism, the list is almost endless.

All the different styles had one thing in common, together with the impressionists. This was the idea of the artist as an unworldly genius. (The stereotype of the penniless artist in a garret wasn't common before the invention of `modern art'.) Art itself became a window into the mind of the artist, a Freudian analysis of the soul. This required an intense inner `vision' and unworldly outsiders who were often a bit mad, like Van Gogh, who chopped off his ear and committed suicide amongst other things. This idea continues today, with artists like Gilbert and George, who say that if they weren't disturbed they wouldn't have anything interesting to make into art.

Along with these ideas of `modern art', art schools abandoned the traditional teaching of the tricks of drawing - add this muscle and the elbow will look more real, even if you can't see it, etc, for the importance of the truth of the artist's personal vision. Books of `drawing methods' continue to be published for `amateur' artists, but  definitely started to be considered cheating. Professional art schools now see drawing more as a way of tapping the unconscious, with jargon like `the importance of making marks'. This, I only recently realised, is why my method of drawing can be considered `cheating'. My pencil scrubbings are my thought processes, the window into my mind, but I have the cheek to rub them out. Though I don't entirely approve, this change in the teaching of art was understandable, there simply wasn't the demand for `realistic' drawings there used to be, particularly because many other technologies besides photography for making images were becoming available.

In the last 10 years a completely different way of making images has become increasingly cheap and flexible, based round computers. Images are drawn with a mouse, or imported into the computer (using scanners and digital cameras), played with using software, and printed out. They are called digital images because they are built up out of long codes of ones and zeroes, or ons and offs inside the circuits of the computer. The final image is divided up into tiny squares called pixels. In its simplest form these squares are either black or white. This is how fax machines and most black and white printers work. Early `9 pin' computer printers made up the letters of the alphabet out of an easily visible arrangement of dots. In each position there was either a dot or no dot. As printers have become more sophisticated, the dots have become smaller. Ink jet printers produce 300 to 600 dots per inch, only visible with a magnifying glass. It is however amazing how much detail the eye can read into just a few pixels.

For colour images, its slightly more complicated, each pixel can be a range of colours instead of simply black or white. I am convinced I can recognise the celebrity's face in only 64 pixels. Put your eyes out of focus and you hardly see the pixels. Advertising hoardings have pixels up to half an inch wide, but you usually don't notice them. The video projector is splitting the image into pixels, though you probably haven't noticed that either. If they are small enough, the pixels start to resemble the texture of colour photos seen under magnification. Each pixel is given a digital code, a string of zeros and ones, according to its colour. A whole image creates very long codes, which is why only computers have only recently become fast enough to deal with images easily.

Digital images offer great scope for cheating. Newspapers manipulate their photos - generally innocent things like this woman carrying a baby - the baby was moved up to take up less space, the idea that ` the camera never lies' is no longer true. It used to be quite obvious if a photo had been messed about with. It's sad in a way, most people assume this photo we took for one of my tv series is a composite image. In fact its a single photo - I'm standing on a huge pile of white waste paper bales, with a slide of the office building projected on the front. I might as well have cheated, or maybe stood in front, making a messier image that would look less like cheating.

The scope for cheating is endless. Several people I know who hate traditional drawing are quite happy doing drawing with the computer - it automatically makes the lines straight and the drawing look neat. Some drawing programmes now offer besides basic line and brush effects, a selection of different famous artists brushes, this is my five minute attempt at a Van Gogh. I don't think he painted dogs, so its not very convincing. Better than this, its possible to import a photo, and using the `auto Van Gogh' command change it into a moderately convincing painting. This works well for most of the great impressionists. So useful enabling great artists of the past to paint scenes from the modern world, you can now create Van Gogh's vision of a petrol station.

It has never been easier to cheat at art. The fine art establishment seems to be carrying on regardless, much as they tried to after the invention of photography. But many people think it is in some sort of crisis, its certainly very pretentious and aspects of it are certainly absurd.

I think the odd thing is that the fine art establishment still regards itself as avante guarde. This cartoon could refer to an exhibition today, but its actually from 1965, and its hardly different from this, from 1912. A tutor told my daughter that anything can be a painting if you call it one, how little has changed since Duchamp put his toilet in an art gallery 80 years ago.