Perspective and Camera Position

Our abil­i­ty to per­ceive depth in pic­tures relies on visu­al cues, the most promi­nent being the rel­a­tive size of objects. It should come as no sur­prise that the lens used to take a pho­to­graph can have a dra­mat­ic effect on our per­cep­tion of depth. Pic­tures tak­en with wide-angle lens­es dif­fer sig­nif­i­cant­ly from those made with long-focus lens­es. The quin­tes­sen­tial wide-angle pho­to exag­ger­ates the size of fore­ground objects in com­par­i­son to objects that are slight­ly far­ther away from the cam­era. Con­verse­ly, long-focus lens­es appear to com­press the appar­ent dis­tances between wide­ly spaced objects, caus­ing them to appear much clos­er to one anoth­er than in real­i­ty. These prop­er­ties are com­mon­ly described using the terms “wide-angle per­spec­tive” and “tele­pho­to per­spec­tive,” respec­tive­ly; the gen­er­al term for these phe­nom­e­na is “per­spec­tive dis­tor­tion.” Unfor­tu­nate­ly, the con­cepts of per­spec­tive and dis­tor­tion are often mis­un­der­stood, even by vet­er­an pho­tog­ra­phers.

Perspective

In pho­tog­ra­phy, per­spec­tive is your camera’s point of view and is deter­mined exclu­sive­ly by the posi­tion from which a pho­to­graph is tak­en. The focal length of a lens doesn’t direct­ly influ­ence per­spec­tive. Whether using a 16mm ultra wide-angle lens or a 90mm long-focus lens, the camera’s posi­tion is the only thing that con­trols per­spec­tive.

Perspective distortion

The char­ac­ter­is­tics attrib­uted to per­spec­tive dis­tor­tion are entire­ly a con­se­quence of the size of the subject(s) and the cam­era-to-sub­ject dis­tance. When an object halves its dis­tance to your cam­era, it will appear to dou­ble in size along its lin­ear dimen­sions (its sub­tend­ed visu­al angle is dou­bled). Con­verse­ly, when an object dou­bles its dis­tance from the cam­era, it will appear half in size along its lin­ear dimen­sions (its sub­tend­ed visu­al angle is halved).

  Try this: ful­ly extend your arms in front of your­self and raise your index fin­gers side-by-side. Then, while keep­ing both fin­gers raised, slow­ly move one hand towards your open eye until it appears twice the width of the oth­er. You will notice this occurs at the halfway point.

Perspective distortion and focal length

Although focal length doesn’t direct­ly cause per­spec­tive dis­tor­tion, it’s often blamed for the effect for two rea­sons. First, dif­fer­ent focal lengths are used for dif­fer­ent pur­pos­es and at vary­ing sub­ject dis­tances. Wide-angle lens­es are typ­i­cal­ly used from short­er dis­tances, lest the sub­ject appears too small in the pic­ture, while long-focus lens­es are gen­er­al­ly used from far­ther away.

Sec­ond, the effects of per­spec­tive dis­tor­tion at the extremes of near and far are betrayed by short and long focal lengths. For exam­ple, if you want­ed to cap­ture the “wide-angle per­spec­tive” caused by a short cam­era-to-sub­ject dis­tance, you would need a wide-angle lens, because the angle of view of a nor­mal (or longer) lens would be too nar­row to ren­der the effect in its entire­ty. Like­wise, if you want­ed to wit­ness “tele­pho­to com­pres­sion,” you would need a long-focus lens because the effect would be ren­dered too minus­cule with­in the angles of view of wide-angle and nor­mal lens­es. Thus, a lens’s focal length makes the effects of per­spec­tive dis­tor­tion evi­dent, but it absolute­ly doesn’t cause them.

Perspective is determined by the position of the camera, not its focal length.
In this exam­ple, you will notice that per­spec­tive is deter­mined exclu­sive­ly by the posi­tion of the cam­era rel­a­tive to the sub­ject and scene, not by the focal length of the lens used to cap­ture the pho­to­graph. Fig­ures A, B, D, and F were shot from the same posi­tion using 105 mm, 50 mm, 35 mm, and 24 mm lens­es, respec­tive­ly. Fig­ures C, E, and G, are enlarge­ments of their adja­cent images, and are made to cor­re­spond to the angle of view of Fig­ure A. These enlarge­ments demon­strate that although the angle of view has var­ied, the per­spec­tive of all com­mon por­tions of the scene remains iden­ti­cal: dif­fer­ent parts of the sub­ject over­lap with the same parts of the back­ground across all four focal lengths.
Perspective is determined by the placement of the camera relative to the subject and scene.
The per­spec­tive of a scene changes with a change in the camera’s posi­tion. Fig­ures A, B, C, and D where pho­tographed with 105 mm, 50 mm, 35 mm, and 24 mm lens­es, respec­tive­ly. To main­tain the sub­ject at a rel­a­tive­ly con­stant size in the com­po­si­tion, the camera’s posi­tion was advanced for­ward in suc­ces­sion with each change in focal length. Thus, after estab­lish­ing a sub­ject size for 105 mm, the cam­era was moved clos­er to cap­ture the pho­to at 50 mm, clos­er again for 35 mm, and even clos­er for the 24 mm shot. Although the sub­ject has remained the same size, the back­ground exhibits a sig­nif­i­cant com­pres­sion, which is a result of the shift­ing per­spec­tive.

Perspective and portraiture

The short work­ing dis­tances used with wide-angle lens­es can exag­ger­ate sub­ject fea­tures and show dis­trac­tions in the back­ground. Com­pared to short-focus lens­es, the per­spec­tives (i.e., sub­ject dis­tances) used with long-focus lens­es to achieve the desired com­po­si­tion can ren­der peo­ple more flat­ter­ing­ly; they also per­mit greater con­trol of back­ground ele­ments due to their nar­row­er angle of view and depth of field.

What is the ide­al per­spec­tive for por­trait pho­tog­ra­phy? The social sci­ences offer sev­er­al clues about favourable cam­era-to-sub­ject dis­tances. Con­sid­er the idea of inter­per­son­al dis­tance zones, which are divid­ed into the inti­mate (0–45 cm), per­son­al (45 cm to 1.2 m), social (1.2 m to 3.7 m), and pub­lic (3.7 m and greater) dis­tances. While these spe­cif­ic ranges may not apply to you—they are from a 1966 study con­duct­ed on Amer­i­can men—you like­ly have an approx­i­mate notion of com­fort­able inter­per­son­al dis­tances. Most of our inter­ac­tions with oth­ers occur in the social range, while most of our non-inter­ac­tive expe­ri­ences hap­pen in the pub­lic range. The aver­age of these dis­tances may act as a guide for the ide­al per­spec­tive for por­trai­ture, because it takes into account the typ­i­cal dis­tances at which indi­vid­u­als are exposed to the faces of oth­ers, there­by nor­mal­iz­ing it.

Fur­ther­more, this can be used to exploit emo­tion­al respons­es to por­traits. A close per­spec­tive is more inti­mate, a far one more dis­tance, and a medi­um one more typ­i­cal.

  The inti­mate and per­son­al dis­tances, which we typ­i­cal­ly reserve for indi­vid­u­als whom we know and trust most dear­ly, tend to ren­der por­traits that rate low for the social traits of trust­wor­thi­ness and com­pe­tence.