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Learning perspective - Page 3 of 4 - Draw Like A Pro


Learning perspective

The objective eye

Things sometimes take a curious turn. The camera took its inspiration from the eye. For a long time people thought it would never be possible to incorporate the eye’s automatic focus system in a camera. Yet nowadays this is a feature of even the most basic cameras. What’s more, cameras are neither short nor long-sighted. Could it be that the pupil has outstripped the master? One thing is certain: most people know more about the working of a camera than they do of the eye! Simplified and exploded view of a camera

Look at this representation of a camera. You see all the main elements: the objective and its lenses, the diaphragm, the camera obscura and the film.

Simplified and exploded view of an eye

Now look at the eye.

Here we find the lenses (the cornea marked 1 and the crystalline lens marked 3), the diaphragm marked 2 (the iris and its pupil), the camera obscura (the upper chamber and the vitreous humour, here marked in orange) and lastly the film, marked 4 (the retina). The reversed image is projected onto the film after the crossing of the rays at the focal point The principle of photography

An object illuminated by light sends rays to the objective. A film sensitive to light is situated in a camera obscura or dark room situated behind the objective. It is marked at the point where it is reached by the rays of light. The rays start by passing through a series of lenses. Obeying the laws of optics, and after meeting at the focal point, they transmit to the film a reduced and reversed image of what was seen in the eyes of the objective.

The reversed image is projected onto the retina like the sensitive film of a camera The eye works in the same way. The rays pass by the iris, cross the crystalline lens and come up to the sensitive retina. The image is reduced and reversed.

The focal point moves according to the shape adopted by the crystalline lens. As long as the lens remains supple we enjoy good eyesight

In a slightly different way to the camera (even an autofocus camera), focusing is carried out by deformation of the crystalline lens (A). The system used to give the image sharpness is too complex to describe here, but the end result is to modify the curve of the two sides of the crystalline lens, thereby varying the focal point and not the distance separating the lens from the sensitive part to be acted on: the retina.

The retina is merely the development of the optical nerve swallowing up visual information

But here’s the most extraordinary part. Our eye has no need of consumables such as a film. Everything works like a digital camera. The retina serves as a film and is lined with tens of thousands of sensitive cells: cones and rods.

This complex, completed by cells and nervous fibres, sends information to the processor, in other words our brain. How is it sent? By radio? No, it’s a cable connection, for the retina is simply the development of the optical nerve. This nerve swallows up the information rather like a funnel. But it has a little defect! The retina is simply the development of the optical nerve which swallows up the visua information. À couper je pense ?

A camera film is flat whereas the retina is curved. Fortunately the brain deals with all that without much difficulty. There is, however, a little snag. The retinal surface has not kept the same sensitive properties in the bottleneck where the retina becomes a tube. This is an area where our eyes do not see, where things are hidden from us.

If you don’t believe me, here’s a little experiment you can try. This experiment designed to expose the blind spot can also be tried after printing out this page

Cover up your left eye and look at the snow crystal with your right eye. Focus on the crystal and you will make out the star. Now move your face fairly slowly closer to and further away from the screen, all the time looking at the crystal with the right eye. At a particular moment the star disappears completely. It is in the retina insensitivity zone. The symmetrical experiment is just as conclusive. The retina has another zone which, as though to console us for this infirmity (disability), is fitted with improved sensitivity. This is the macula. The macula is lavishly provided with cones and takes better “photographs” than any other part of the retinal surface.The quest to find the laws of perspective gave rise to the (an) experiment with the interposed glass pane. The experiment took place at a time when photography was still unknown

The experiment is known as “Leonardo da Vinci’s window”. In this photograph, taken in 1890, the artist views the perspective of the mulberry tree ou on garde le nom français ? courtyard of the Paris School of Fine Arts. By placing a pane of glass vertically in front of you, closing one eye and keeping your head very still, you can trace the contour of what you see, just as you would trace an image already reduced to two dimensions. The fact is that when you close one eye, all effect of depth is crushed. So what you get is a perfect drawing in perspective without knowing the slightest thing about the theory of perspective! When masters like Leonardo da Vinci and Dürer studied the results, they noticed that certain lines, in reality parallel, sur la vitre converged towards the horizon, while others remained resolutely parallel to each other.

Of course, it wouldn’t be very practical to set up a glass pane every time you wanted to draw, so we’ll make do with closing one eye and paying careful attention to what we see. This will be enough to get rid of any effect of depth. When you close one eye, the real world becomes an image in exact perspective which you can use for your drawing. A photographer doesn’t complicate things by worrying about the rules of perspective. What was far or near in reality paraît is far or near in his photo. The easiest way to understand perspective is from a photographer’s point of view, the difference being that you don’t actually need a camera, just your eye.

Stand in the corner of a room and turn round to face towards the middle. Stretch out your arms and hold the two ends of a ruler horizontally in each hand. Close one eye and “take a photograph” with the other one. Don’t move your eyes and move the ruler over the photograph , taking care to keep it horizontal. You see that the horizontal lines are biased and slanting just as in the picture we studied a moment ago. How many lines which are horizontal in reality still seem horizontal with one eye closed? Almost none. So all you have to do is to transpose your observations as faithfully as possible onto your drawing paper. You can’t go very far wrong as far as perspective is concerned.

At the outset, it’s always easier to draw a subject which exists physically in front of your eyes. In this way you can observe and take note of measurements, proportions and angles. But very soon you will want to draw from memory or your imagination and here your knowledge of perspective will come in useful. If you have encountered a sufficient number of different situations you will know how to avoid the tricks which perspective will try to play on you. I promised you that I wouldn’t bore you with a lot of rules. But in this case I must at least show you the dangerous corners, where perspective lies in wait for you and tries to spoil your drawings…

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