Introduction to Microphotography

Microphotography is the extreme form of macro photography, dedicated to the photography of small objects from life-size to modest enlargements of up to about 20

One of the most popular books that I read during my childhood was Eric in the Land of the Insects, written by the Dutch author Godfried Bomans. In this humorous fantasy, nine-year-old Eric enters the landscape painting that hangs on his wall and he discovers a world of man-sized wasps, bees, butterflies and other insects that is stunningly similar to the world of humans.

The book made such an impression on me that I have always wanted to explore such a world full of wondrous creatures myself.

Once photography became a part of my life and I purchased the Canon extreme macro lens MP-E 65 mm/f2.8, which has a maximum magnification of 5:1, my world was populated with grasshoppers, spiders, snails, flies, dragonflies and butterflies—Eric’s world.

 The compound eyes of insects, consisting of a large number of ommatidia, have always fascinated me. To uncover as much detail as possible I photograph insects so extremely close that they seem to have a gigantic size. At that scale insects of the same species look very different and each insect seems to have its own character.

I am very interested in the behavior of insects and take only micros during the day time period when they are actively foraging.

 

Microphotography And  Magnification

Magnification describes the relationship between the actual size of the subject and the size of its image on the sensor of the camera. Photographing a 3 cm (1.18 inch) long blue-tailed damselfly so that its image size is 1 cm (0.39 inch) on the sensor means that the magnification is 1/3 (1:3) life-size.

Dividing the size of the subject’s image on the sensor by the actual size determines the magnification. At 1:1 life-size, the size of the subject on the sensor is as big as it is in real life. Macro photography is restricted to magnifications in the order of 1:10 to 1:1 life-size.

When this magnification is reached, shooting from life-size to modest magnifications of up to 20 is called microphotography. Greater enlargements are possible with a microscope: from about 20 with a standard microscope to over 1500 with a research microscope. A camera may take the place of the eyepiece of a microscope in a basic outfit.

Larger than Life-size

Most macro lenses are maximally able to capture a 1:1 life-size image of a subject on the camera’s sensor. Strictly speaking, a lens is categorized as a macro lens only if it can achieve this 1:1 magnification. Microphotography can be undertaken by normal macro lenses equipped with modestly specialized equipment.

A lens’ minimum focusing distance is the closest distance your macro lens will allow you to get to your subject while still maintaining sharp focus. A low-budget method to decrease the minimum focusing distance is to extend the distance between the lens and the sensor by inserting extension tubes or a continuously adjustable bellows.

Both the extension tubes and the bellows do not contain optical elements. The further the lens is from the sensor, the closer the minimum focusing distance, the greater the magnification, and the darker the image given the same aperture. Tubes of various lengths can be stacked, decreasing lens-to-subject distance and increasing magnification. Extension tubes and bellows can be used for different lenses. A small disadvantage is that the use of extension tubes and bellows may not preserve autofocussing, auto exposure and auto aperture operation.

The maximally obtainable magnification can be calculated with the following simple equation: D (length of the set of extension tubes or the bellows) + F (focal length of the macro lens) ÷ F = magnification.

For Example: Adding a set of extension tubes with a total length 0f 60 mm to a 60 mm macro lens will give maximally a magnification of (60+60) ÷ 60 = 2.

By adding a teleconverter, an even greater magnification can be achieved. Application of a 2x teleconverter produces a maximum magnification of 4 and 2 stops loss in light intensity. Adding more glass means a drop in quality and quantity of light transmission, the extent of which depends on the quality of the particular teleconverter you’re using.

Placing an auxiliary close-up lens (or close-up “filter”) in front of a macro lens is another option. Inexpensive screw-in or slip-on attachments provide close-focusing at a very low cost. Some two-element versions are qualitatively very good while many inexpensive single element lenses exhibit chromatic aberration and reduced sharpness of the resulting image.

When you use macro lenses with different diameters, for each macro lens a close-up lens has to be purchased separately. Most close-up lenses are marked with a +d number in diopter unit, the power of the lens. The diopter (or power) of a lens is defined as 1000 ÷ F_d, where F_d is the focal length of the lens measured in mm. Thus, a lens with a focal length of 50mm has a diopter of +20 = 1000 ÷ 50, and a +4 diopter close-up lens has a focal length of 250mm = 1000 ÷ 4.

The maximally obtainable magnification can be calculated with the equation (2F + F_d) ÷ F_d.

For Example: coupling a +20 diopter lens with a 60 mm macro lens produces maximally a magnification of (2 × 60 + 50) ÷ 50 = 3.4.

An interesting alternative is the reverse lens technique which can be accomplished by mounting a lens with focal length F_r in reverse, in front of a normally mounted lens of greater focal length F, using a macro coupler which screws into the front filter threads of both lenses. The maximally obtainable magnification can be calculated with the equation F ÷ F_r.

Depending on the quality of the reversed mounted lens, a drop in quality and quantity of light transmission may negatively influence the image quality. All discussed techniques can be used in conjunction to obtain even larger magnifications.

 

 

Sharp Images

Working with large magnifications means that the subject is only a few centimeters in front of the lens. During the day time insects move from feeding place to feeding place or are hunting. They stop only for very short periods of time at a specific place to forage, which means that there is no time to set up a tripod.

One needs to hand-hold the camera to make the photos. Light is lost when using macro lenses, extension tubes and teleconverters. As magnification increases, depth of field decreases rapidly. Due to loss of light and depth of field considerations, it is advisable to use a ring flash or twin lite flash when shooting micros.

It will allow you to shoot at a reasonable speed, yet enable you to use a small aperture for sufficient depth of field and a fast shutter speed (e.g. 1/200 sec) to capture moving insects. Magnifying the image also magnifies any movement of the camera and the subject, so it becomes far more challenging to make super sharp images.

Depth of field, which is the zone of acceptable sharp focus, becomes very shallow at high magnifications. For instance, at five times life-size, the depth of field of the MP-E 65 mm at f/11 is 0.2 mm. It is critical to focus carefully in microphotography since the limited depth of field available isn’t sufficient to mask minor focusing errors.

I always manually focus on the eye(s) of an insect and align the focusing plane in such a way that a major part of the head is sharp.

With thanks to Jos Plas and Frans Mulder for their constructive comments and enthusiastic support.

by Huub de Waard
Article: © 2011 Huub de Waard. All right reserved.