ABSTRACT
There is a peeuliarity of human VISiOn that is especially noticeable in drawing landscape from nature, and even more so when drawing it from memory, We tend to exaggerate the si~e of objects that interest us, The habit may relate to the Egyptian method oi' seleetive emphasis, but would-be copyists are also subject to it. It might be called 'the mental zoom',
If we were gran ted the ability to redesign the hwnan eye, a remarkable instrument but not without its defeets. we might givc first priority to the improvement of the mcchanism for accommodation; that is, for foeusing over widcly varying distances, thus avoiding the need for spectacles at any age, Ifthis idea had arisen !tom a eomparison with thc camera, our sccond illlprovement might be to provide a natural zoom lens, freeing us from the restrietions of our single, fixed foeal length, We eould then switeh at will from a general, wide-angle view to a dose enlargelllent of a narrow field, without necessarily going so far as to supersede the telescope and the lllicroscope, Social habits would of course havc to be drastieally revised; we would lose some privacy, but gain some insight into others' habits; undue attention to distant details would lead to pedestrian eollisions and trafik accidents until we got used to our new faeulty. Eut to some extent we seem to have that I'aculty already. Although the eye has no zoom mechanism, the mind' s eye acts as if it had something rather like it. Move from one seat in a cinellla to another much further back, and the screen may look uncomfortably smalI. but within a few minutes, given normal eyesight. the dilference is forgotten. Our area of sharp vision having a coverage of only about 2 degrees ronnd the centre of concentration, the main elfeet of moving to a back seat is only that less shifting of that centre is required when following the action on the sereen,
See a distant object through a small window on the far side of a room, and it looks nearer and bigger than it would frolll the window itself, in which
view thc surrounding landseape would dwarf it. As you approach the window, everything outside seems to shrink and reeede, at least as much as the window may seem to enlarge and approach, Move back from thc window, and the distant object expands again, Althongh no such change wonld occur if the same dcgree of movement were made out of doors, prolonged attention to the objeet ean have a similar eITeet: not, of course, on the retinal image but on the mental concept. There is ample evidence in landscape drawings, both amateur and professional, for this subjective magnification,
It is cspeeially with regard to the height of a distant objeet that we make an alm ost systematic overestimate, and not only when drawing the unseen from memory, for drawing from nature is always an act ofmemory in that we cannot concenh'ate on the subjeet and the drawing at the same time, Gilbert White described the Sussex Downs as 'majestic mountains', That gentle escarpment can indeed look alm ost c1ilT-like from below, but a sustained grass slope of more than 30 degrees is rare anywhere. Looking down from the ridgc, one' s viewpoint seems far more elevated than it wonld appcar on a section ofthe terrain drawn to scale, as Hilaire Belloc observed ofthose same Downs (15,1), He detectedso much exaggeration ofheights in his own sketches of Alpine landscape, when pilgriming on foot to Rome, that he demonstrated the degree of crror in further sketches based on careful measurement of ihe truc angles, It is significant perhaps that in his youth he had served in the French artillery. From ancient times cartography has been primarily a military art. The Egyptians, the Assyrians and the Romans all made illustrations of specific lands capes with reference to military campaigns, 'Ordnance' is artillery, and the Ordnance Survey of Britain was originally carried out by the Master General ofOrdnance. In the Second World War, a gnnner officer was still expected to be competent in drawing landscape and to understand its pcrspeetive. In ill-mappcd frontier
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