Magnification in Photography

Magnification in photography is the ratio of the size of the subject on the sensor/film to the real size of the subject. It is a property of lens, and expressed in terms of a ratio.

Magnification =
object-size on sensor ÷ real size of object

Table of contents:

• ● Magnification in photography
• ● Magnification ratio
• ● Magnification and Focal Length
• ● Magnification and sensor-size

Following is a set of tiny flowers, but due to the shortest lens-to-subject distance and medium long focal-length used, magnification has worked here. The flowers were so tiny, that you almost cannot see them without sitting on the ground.

f/9, 1⁄320 sec., ISO-400, FL-85mm eqv., Nikon d810, Nikon 70-300mm f/4.5-5.6

Magnification ratio

If a 10 cm. tall object is projected as 5 cm. on the sensor/film, then the magnification ratio is said to be 5:10, or 1:2.

Again, if a 4 inch tall butterfly is projected on the sensor/film as 4 inch image, then the magnification ratio is said to be 4:4, or 1:1; this is also known as life-size magnification.

If any lens is said to have 3:1 magnification capacity, then on the film/sensor it will produce a 15mm image of an ant, which is actually 5mm in size. Dedicated macro lenses have such powerful magnification capacity. In all the cases, maximum focus distance (MFD) of the lens is to be used.

f/11, 1⁄320 sec., ISO-2800, FL-157mm eqv.,
Nikon d7000, Nikon 18-105mm f/3.5-5.6

This tiny dragonfly was magnified using the shortest possible lens-to-subject distance, i.e., the minimum focus distance (MFD).

Magnification and Focal Length

Focal length contributes to the magnification of a subject. A longer focal length produces high magnification, while a shorter focal length produces less magnification. In photography, magnification of a subject depends on two factors, focal length and lens to subject distance.

The relations between lens-to-subject-distance and depth of field and focal length and depth of field are very important aspects in photography.

f/11, 1⁄320 sec., ISO-3600, FL-78mm eqv.,
Nikon d810, Nikon 70-300mm f/4.5-5.6

Factors effecting magnification

Magnification depends on:
1 - Focal-length,
2 - Lens to subject distance.

Depth-of-field depends on:
1 - Magnification,
2 - Aperture.

Magnification and sensor-size

Does magnification depend upon size of the sensor ? NO. Please check the following image :

Same lens is used on different sensors to apply a reproduction ratio of 2:1. So, all the three images acquire same magnification (2x). But the micro 4⁄3rd sensor seems to have highest magnification when viewed on the screen, because it fills the sensor more than the APSC & Full-frame sensors.

f/5.3, 1⁄200 sec., ISO-125, FL-184mm eqv.,
Nikon Coolpix L820

The magnification factors are sometimes written on macro lenses. Remember that a magnification or reproduction ratio of 2:1 is sometimes mentioned as 2x magnification; so 3:1 may be read as 3x, and 1:2 may be read as 0.5x magnification.

f/4.5, 1⁄1000 sec., ISO-125, FL-105mm eqv.,
Nikon Coolpix L820