It is widely known that a bonsai can be described as having form and style.

The form describes the shape of the trunk (sometimes also referred to as its style); the form might be informal upright, cascade or broom for instance.

The bonsai style is the term used to describe the manner in which the tree is styled and presented; a classical 'Japanese' style with horizontal branching as one would expect a Pine to be or a naturalistic style, showing branching one would expect of a deciduous tree.

A third equally important descriptive term might be considered is the view at which the tree is seen. Is the tree seen from up close, as if standing at its base looking upward (short view) or at a distance as though seen on the horizon (the long view)?

Why is establishing the view important?

Trees seen in the near view exhibit much different features to those seen from afar; trunk taper, branching, foliage density, even the appearance of any deadwood is entirely different.
If near view and far view features appear on the same tree, a confusing image is presented to the viewer and the ideal presentation of the tree is lost.

Near View Trees

Near view trees are seen as though standing at their base looking upwards into the branches.

Swamp Cypress at Tatton Park, UK. On the left seen from the long view, on the right from the near view.

This is the view that is more popularly described for bonsai.
The trunk at the base (beside which the viewer stands) is the widest point and can appear to be massive. Looking upwards, perspective means that the trunk thins as the eye travels up the trunk; this means that the top of the trunk, which is furthest from the viewer, is very narrow in comparison to the base.

Even on a fairly uniform trunk, seen from below the perspective will create the illusion of taper. The greater the amount of taper between the base of the trunk and its top, the more the tree appears to tower over the viewer. In terms of bonsai, a trunk ratio of 6:1 or greater (height: trunk diameter) is used to convey an image of a tree towering over the viewer. The lower the ratio, the greater and more severe the image becomes.

Far View Trees

Far view trees are seen as though they are on the horizon in a landscape.

Scots Pines seen in Norfolk UK, in the long view

This view is commonly used for group plantings and literati form trees but it can be used as equally for any form such as informal upright or broom bonsai.
The base and the top of the trunk are seen from the same perspective; that is, they are seen naturally. The trunk does naturally taper from its widest point at the base up to its thinnest point in the apex. However, unlike a trunk seen in the near view, the trunk taper is less severe as the perspective does not 'add' the illusion of taper.

One of the same Scots Pines seen from below in the near view.

The severely tapered trunk of the tree seen from its base (near view) loses much of its taper when seen from a distance.
In terms of bonsai, a ratio of 6:1 or less (anything up to 15:1) is used to convey an image of a tree seen at a distance.

Trunk taper defines the view

When styling a tree for bonsai, the shape and movement of a trunk define the form of the bonsai. That is whether it will be an informal upright, a cascade or formal upright.
In the same way, the taper of the trunk defines the view of the bonsai.
A well-tapered trunk with a trunk height to trunk diameter ratio of approximately 6:1 or less is suitable for a bonsai in the near view.
A trunk with slow/slight taper with a height to diameter ratio of 6:1 or more will be suitable for a bonsai in the far view.

There are subtle differences when styling trees of one view or another. A well-designed bonsai will reflect the view at which it is seen throughout the styling process, from the structure of its branching to the choice of the final pot. Mixing near-view and far-view characteristics will produce a confused image of a tree.

Near View Characteristics

A tree in the near view will have the following characteristics;
In this (near) view, the branches will appear to be very wide. Standing at the base of a tree, the branches reach a long way to the left and the right; an approximate foliage width (at the base) of 2/3 the height of tree's height is appropriate for an informal upright design.

As the branches are seen from the same perspective as the well-tapered trunk, the branches should also diminish noticeably in size the higher up the trunk they are. The first branches will be long and thick, the uppermost branches short and thin. This creates a foliage mass that is overall triangular. Create branches of similar thickness and length on a heavily tapered trunk and the perspectives are a mixed up and will not look satisfactory.
Seen from below in the near view, the foliage mass is dense and heavy. Little light is able to penetrate through the branches.
Deadwood features should be more heavily grained as they are seen closer up (in the near view) it should be possible to see that natural deadwood (jins and shari) are not just a smooth expanse of white wood.

Cedrus libani at Tatton Park with light branching, less dense branching; negative space is evident.

The same branches seen from below are very dense

Far View Characteristics

A tree in the far view will have the following characteristics;
The branching appears a more natural width. Approximately 1/3 the overall height of the tree for an informal upright design. From this far view, the branching is seen at a distance and is more natural. The branches from base to top of the trunk have less difference in thickness and are of more similar width; the familiar scalene triangle is less pronounced or even absent. (Note that the lower branches should still be longer and thicker than those at the top, however, there should be less exaggeration than when seen from the near view perspective).
The foliage canopy should be lighter. At a distance, the mass of foliage should be broken up with negative space (areas without foliage).
Deadwood features have less detail; if the viewer is to be made to believe that the tree is a distance away, highly detailed jin and shari should not be visible.
Bonsai in the far view should be planted in shallower but wider pots that create an impression of a landscape.

Why is it necessary to establish the view at all?

Many of the bonsai rules, or more properly, guidelines, are aimed at producing an image of a tree as seen from below (in the near view). This can dictate a trunk height to diameter of 6:1 or less, heavy lower branching and lighter branching in the apex and a foliage mass that forms a triangular shape.
But, in trying to create a more natural, realistic bonsai, one can also take a more natural view of a tree. That is, as seen from a distance where the rules of perspective have less influence on the overall design.
The majority of trees, both young and old, do not have massively tapered trunks; in fact the majority of old trees we see in our day-to-day lives have trunks with quite slow taper.

However, to portray a natural tree seen from a distance, one also has to reflect the natural characteristics of a tree seen from a distance.
Using near view characteristics on a slow tapering tree will very often just produce a bonsai that simply looks very young and immature instead of an image of an old tree seen on the horizon.

Finally.....

In writing this article I have given two extremes by way of explanation; a tree that is seen from its base and a tree that is seen in the distance. There is no reason why a tree has to be strictly one or the other; there are a range of views in between. The range and subtlety of these characteristics should therefore differ accordingly.

The trunk height to trunk diameter ratio of 6:1 that is often spoken of, is a guideline. Material that has pronounced trunk taper but has a ratio greater than 6:1 is still suitable for bonsai, just not in the near view.

Whether it is the slow, subtle taper of a tree seen faraway or the heavy, abrupt taper of a tree seen close-up, all bonsai should have trunks with a degree of taper. A bonsai without taper will always look like a young tree!