Understand a Macro Lens’s Features
A macro lens’s features are basically its main selling points. Photo companies like Canon and Nikon use these features to compete with each other and also to convince you to go with the more expensive lens. Make sure that you are well informed about lens features so that you know which ones you need.
Here are the common features associated with macro and close-up lenses:
Focal length and maximum aperture describe the focusing distance, angle of view, and speed of a lens.
Aperture determines how much light your lens can allow in at one time. A lower number represents a larger max aperture, which allows more light in, creating a faster lens. (The term fast is used because a large aperture enables photographers to use a more rapid shutter speed.)
Focus adjustment refers to how a lens focuses. Some wider macro lenses extend away from the camera in order to achieve focus on close subjects. This may scare off some subjects or even come in contact with some elements in your scene. A selling point to higher end macro lenses is that they usually have a fully internal focusing system so the lens never extends farther from the camera.
The closest focusing distance describes how close a lens will enable you to get to a subject while still achieving focus.
Image stabilization (IS) gives you sharp results when handholding your camera during an exposure. The IS can freeze the image in place even when your hands are shaking.
A floating system enables multiple lens groups inside a particular lens to move independently of one another in order to maximize quality at different focusing distances. A floating system enables a lens to produce high quality images from all focusing distances rather than working better at one distance than another.
Extra-low dispersion minimizes chromatic aberration (the separation of different wave lengths of color after refracting through a lens). Chromatic aberration can cause issues in an image when the red waves of light are focused onto a different point than the green and blue. This results in halos of color around your subject such as in the example. Notice how the right side of the subject has a red halo, which is balanced by a greenish-blue halo on the left.
100mm, 1/250, f/3.5, 400
Flat field refers to a macro lens’s ability to receive light and provide a uniform signal to the digital sensor at very close distances to the subject. This ensures that your plane of focus (the area in front of the camera where focus is achieved) is level and parallel to your digital sensor.
If a macro lens is said to be multi-purpose it means you can use it for both macro and ordinary shooting. A macro-only lens can’t be used for anything but macro and close-up photography.
A coated lens may produce sharper overall image quality and a higher quality color reproduction.
The lens’s diaphragm refers to the shape of its open aperture. The diaphragm affects how light sources in your frame and blurry elements are represented. A rounder opening produces a more round appearance of blurred edges, while a ridged opening produces a more ridged appearance. The photo shows an example of different diaphragm shapes paired with their accompanying image results.
The lens dimensions tell you just how big and heavy a lens is.
Be sure to read user reviews on specific lenses before making a purchase. And always be prepared with a good knowledge of the product before entering into a sales situation, as some salespeople can be a bit slick. You might also want to research which off-brand lenses work with the specific brand of your camera, as these companies usually offer similar products with lower price tags.