To achieve this, the lens generally must have a very short minimum focal distance to get the object physically close to the lens and sensor. This makes macro lenses ideal for close-up photography and still-life work. Some can even “switch hit” to produce beautiful portraits.
Macro Lens Magnification and Reproduction Ratio
Some macro lenses are capable of creating images larger than their real-world counterpart, described as a “magnification ratio” in most technical specifications. When considering magnification, a multiplier greater than 1x indicates the image can appear larger than the real world object by the scale of that multiplier. Some zoom lenses marketed to include “macro” features may only reach 1:1, and only at an extremely narrow slice of the focal distance. Other purpose-built macro lenses can achieve more than a 1x magnification throughout the focal distance. General-purpose macro lenses will achieve a maximum magnification factor of 1x, or a 1:1 reproduction ratio. These lenses make up some of the most popular “macro” offerings, so it’s important to check magnification values. Special-purpose macro lenses can achieve impressive magnification ranges, but won’t be as useful for general purpose photography, thanks to this property. As a rule of thumb, if a macro lens can achieve a magnification factor greater than 1x, such as 2x (2:1) or higher, it will be best suited to dedicated macro work. Thanks to the specialized optics required for higher magnification ratios, that lens might not “switch hit” as a general purpose lens as easily.
Common Misunderstandings About “Macro”
Despite the technical definition, the word “macro” is used liberally in photography marketing and online discussions. When people use this word, they might be describing a close-up photograph, a short focal distance, a lens with macro-style capabilities, or a true macro lens. There’s no way to say for sure, except in context. That being said, a macro lens is generally understood to be any lens capable of extreme close-up photographs. In advertisements, the rules are adhered to more closely. Because manufacturers can be sued if they lie in advertisements, legal departments pay close attention to the exact definition of technical terms. When you see the word “macro” in advertising copy, take care to analyze its precise meaning. Are they describing an actual lens capable of reproduction ratios approaching 1:1, or some other feature of the product? Careful reading can help make their intention clear.
Macro Lens Characteristics
The visual effect can be startling and otherworldly. Because macro lenses “break” the 1:1 reproduction ratio, small objects can be captured in enormous detail, providing a closer look than your eyes alone can capture. This effect is what unlocks the impressive detail of macro-scale photographs. Details can be rendered larger than they actually appear, providing a unique perspective on the micro-scale world. The optical design of macro lenses also requires extremely close focusing distances. The closest focal distance tends to be between 30 cm (about 12 inches) and 10 cm (about 4 inches)—far closer than most other lenses. This permits extreme closeup work, and allows for the enlargement that most macro lenses can reach. Most purpose-built macro lenses are fixed length prime lenses of the telephoto range, but zoom lenses can also be built with a macro-focusing range. While macro lenses do not require a specific focal length, the optical qualities of a moderate telephoto tend to produce the most functional macro lens. The optical requirements of macro lenses mean that maximum apertures are generally smaller than prime lenses of similar quality. Most quality macro lenses have a maximum aperture of around f/2.8, similar to telephone zoom lenses. Thanks to their longer focal length, macro lenses typically require a shutter speed of at least 1/125. To avoid any camera shake, a macro lens will often will require intense lighting or a tripod for a sharp exposure.
Extension Tubes vs. Macro Lenses
The easiest way to create a macro lens is to extend the distance between the back element of the lens and the sensor plane. This has the effect of producing a larger image circle, increasing the apparent size of the image on the sensor plane. While this does not technically create a macro lens, it produces a visually similar effect by optically “cropping” the image cast by the lens, in a similar way to how a crop sensor camera only captures the center of a full-frame lens’ image circle. This typically comes at the expense of infinity focus. While your lens can focus on objects that are closer to the plane of the lens, it also does not allow the lens to reach its maximal focus distance at infinity focus. Macro photography extension tubes contain no glass or optics, making them inexpensive and easy to manufacture. These cheap, lightweight accessories provide enough flexibility to explore the style without making a major financial investment. As a result, these extension tubes provide an easy entry point into macro photography for most users. If you find the effect interesting and the practical restrictions worthwhile, then you’re likely to benefit from actual macro-capable lenses. Considering these are typically expensive and comparatively unpopular, you may not want to invest until you’re sure it suits your work style and subjects of interest. That said, all but the most specialized macro lenses can function as highly-capable telephoto lenses. They may pay for the macro features with a slower maximum aperture, but the optics of a macro lens are not fundamentally incompatible with any kind of photography. Their close-distance performance doesn’t preclude their use in other types of photography, and the common macro focal length of 100mm can make a capable portrait lens. It’s wise to investigate macro photography by renting a macro lens or using some extension tubes. If you find the results appealing, explore the style until you start to feel restricted by the limits of your equipment. At that point, it’s smart to invest in a macro lens that removes the restrictions you find to be the most frustrating.
