Tag Archives: Lupinus texensis

Why do macro lenses come in several different focal lengths?

Which one do I need?

TX Bluebonnet-3560-Sm

Texas Bluebonnet, Lupinus texensis. This flower was photographed  at half life size on the sensor (0.5X) with a Nikon macro lens. Which focal length was used?

True macro (or Micro) lenses allow subjects to be photographed much closer than normal minimum focusing distance, thus greatly magnifying the image size. Often, these are prime lenses of single focal length with various focal lengths available from each manufacturer. And macro lenses produce high quality images. Because these are complete lenses that focus to infinity, many other uses of high quality are possible.

Macro lenses are the more expensive of the alternatives to focusing close. Most retain all automatic features, but have limited magnification range, frequently up to 1:1, or life size. With accessories they can produce magnifications from 1.0 X to 40.0 X life size. Because no lens extension is required per se, little exposure compensation required.

Most manufacturers make more than one macro lens. Canon, Nikon, Olympus and others produce high quality macro lenses. True macro (or micro by Nikon) lenses are produced in various focal lengths, commonly from 40mm upwards to 200mm. And they may all focus very close; most focus to life-size or 1.0X. (Also called 1:1.) Essentially, they all do the same thing.

_BKL6994-Sm

Three Nikon macro optics (clockwise, from near left) 60 mm F 2.8 AF Micro Nikkor, 200 mm F 4.0 AF Micro Nikkor, and 105 mm F 2.8 AF VR Micro Nikkor.

So if that is true, why would there be a variety if they all do the same thing? The answer is simple: working distance. Working distance is the actual distance between the subject and the camera’s sensor when the lens is focused. As the focal length of the lens increases, the working distance also increases at the same image magnification.

Let’s look at the working distances provided by three popular focal lengths above: the 60mm, 105mm and 200mm macro lenses. All these lenses below are accurately focused at life size or 1.0X and the reproductions are at the same scale. Canon has lenses in similar focal lengths; the 60mm F2.8, 100mm F2.8 and the 180mm F 3.5 lens trio. All are magnificent optics to be sure.

Nikon Macro Lens

This lens is the 60mm F2.8 Micro Nikkor focused on a small portion of the flower at life-size. It focuses to 1:1 at 8.6 inches.

Nikon Macro Lens

The second is the 105mm F2.8 Micro Nikkor. It focused to 1:1 at 12 inches.

Nikon Macro Lens

This last lens is the 200mm F4.0 Micro Nikkor. It will focus at 1:1 at a distance of 19.2 inches.

Working distance is important to macro photography. Greater working distance allows several advantages. These include the freedom from making a shadow on the subject, the ability to get ample light or lighting fixtures onto the subject, the ability not to frighten or run off a live subject and the ability to work at a safer distance from a dangerous subject.

One additional attribute to remember is that the angle of view of any lens gets smaller as the focal length increases. So as a result, a 200mm lens focused at 1:1 will have an area of coverage of one half that of a 100mm macro lens at the same magnification.Three Focal Lengths-Sm

These three images were made with the macro lenses described above.  In making the photographs, emphasis was given to producing the flowers at the same size in each frame in the camera when shot. To do so the image with the 60mm lens is made from fairly close; the 200 mm lens much farther away.

The resultant images look the same, but upon close inspection there are notable differences. First, the longest lens tends to compress the image more than the other two. The distant flower looks closer to the close one. This is an example how the focal length of the lenses affects perspective. The second difference is an apparent difference in angle of view. Notice the black form in the upper right of the images. We see less of it in the 60 mm view and it tends to move and get larger as the lens focal length gets longer. Otherwise, there is little difference perceived in the three images. Because the subject size is the same in the three images, the Depth of Field is also the same. All images were shot at the same F5.6 aperture.

So, to answer the question: The lens that’s right for you depends upon your most common use. If you need a lot of accessory lighting like flashes, diffusers and other modifiers in your set up, you may enjoy the freedom of the longer focal length/longer working distance. If you want a real compact lens, then the shorter lens may be perfect. A good compromise and my recommendation is the 105 mm F2.8 AF VR Micro Nikkor.

Copyright © 2014 Brian Loflin. All rights reserved.

 

 

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