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1. Introduction
2. Classification
3. Recommendations on choosing a macro lens

1. Introduction
All true macro lenses have a fixed focal length and achieve 1x magnification (reproduction ratio 1:1) very easily. The difference between them and the non-macro lenses is that they’re designed to attain high image quality and high sharpness throughout the frame at minimum focusing distance.

Most macro lenses’ widest aperture is f/2.8, except the long focal length lenses, whose widest aperture is f/3.5 for obvious reasons. You would rarely shoot macro at widest aperture because of the shallow depth of field you will get, so aperture affects mainly convenience when focusing manually.

As with non-macro lenses, macro lenses can have internal focusing. Their main advantage is that their length doesn’t increase during focusing and they don’t tend to collect dust.

Since all macro lenses can double as standard lenses, most of them feature a switch to limit the focusing distance within a certain range. This can be very useful when you’re using autofocus and you know in which range your subject is.

Some macro lenses have image stabilization, for example Canon EF 100/2.8 USM L IS macro. It couldn’t do any harm, but I wouldn’t rely on it alone. If I decide to shoot a scene using only natural light, I would rather use a tripod for this purpose. Image stabilization not only makes the lens more expensive, but it also increases, if slightly, its weight.

2. Classification
Macro lenses are mainly classification by their focal length. As we know, it determines the angle of view and perspective. In the past, macro lenses would be divided in three groups – 50-60 mm, 90-105 mm and 180-200 mm. Today, these borders are rather blurred and there is larger variety of lenses out there, but the differences between the three groups remain the same.

It is seen from the table above, that increasing focal length increases working distance to the subject, at the same magnification. This is the main difference between different lens groups and it is due to the different angle of view. Some photographers prefer to shoot their subject in its natural environment, because this way they can achieve more interesting results, but it is a common practice to isolate the subject using a nicely blurred background which doesn’t distract too much.

If we compare three pictures, shot at focal lengths 50, 100 and 180 mm respectively, at the same magnification (1x) and f-number (f/5.6), the picture shot at longest focal length will appear to have the most shallow depth of field. In fact, the depth of field will be the same in the three pictures (0.75 mm), because it depends only on the magnification and f-number. The illusion of shallow depth of field is due to it being shot at minimum angle of view. For this reason, a smaller part of the scene is captured in the background, which contributes to it being more blurred. The small angle of view also makes handholding much harder.

As you can see, increasing the focal length leads to increasing the size and the weight of the lens. Their higher price is also due to this.

3. Recommendations on choosing a macro lensYou will hardly find a bad macro lens, so the choice is reduced to making the right decision depending on the purpose you’ll be using it for and the result you want to achieve. Depending on what you’re gonna take pictures of, and what magnification you need, you can easily determine the focal length you will require.

 If, for example, you’re going to shoot product photography, you can select a lens from the shortest focal lengths group (40-70 mm), which are also the cheapest. For this kind of shots the small working distance would hardly be a problem to you. The background will be arranged by you, so the wide angle of view also shouldn’t worry you. It is assumed that you’ll be using artificial light, so you wouldn’t throw a shadow on your subject even when shooting at maximum magnification. Howsoever, if money is not an issue and you’ll be shooting rather small subjects, I would prefer 90-105 mm focal length. The extra working distance could only help you.

 If you’re intending to shoot insects, 90-105 mm lenses are a much better choice. Their longer focal length results in bigger working distance and there is a smaller chance of scaring your subject. You also wouldn’t throw a shadow on it so easily, if you’re using only natural light. The longer focal length means narrower angle of view, but handholding is still not a problem. They’re also very suitable for getting beyond 1x magnification by using various accessories. If, for example, you’re using a full set of extension tubes (68 mm), you’ll get almost 2x magnification, because focal length of most of these lenses becomes nearly 80 mm at 1x magnification, because of the peculiarities of the focusing system. Due to all these reasons, I would recommend getting a lens from this group if you don’t have a lot of experience in macro photography. They’re more expensive than the 40-70 mm lenses, but the difference in the price tag is definitely worth it.

 If you want even more working distance, then you can think about a 150-200 mm lens. The biggest advantage of these lenses, besides the largest working distance, is the “compressing” of perspective. This means that you’ll easily get a nicely blurred background, which, from an artistic standpoint, helps you accent on the main subject in the picture. This, however, is a result of their narrow angle of view, which makes them difficult for handholding. This is also their main disadvantage. Besides that their greater weight makes things even worse, so the best way to use them is with a tripod. Even if you wish to use artificial light, you’re way too far from your subject, which makes things even more complicated.

 If your goal is magnification beyond 1x, then the best solution is the Canon MP-E 65. This is the only lens that offers 1-5x magnification without any additional accessories. Focus on infinity is not possible – the maximum focusing distance corresponds to 1x magnification, so the largest subject you’ll be able to shoot will be the size of your camera’s sensor. Naturally, there are many other ways to get beyond 1x, but they would hardly deliver higher image quality. This lens doesn’t have an autofocus. With the focusing ring you change the magnification and focusing is achieved by moving the camera back and forth. Not only focusing, but sometimes even finding the subject in the viewfinder is sometimes difficult for someone without the sufficient experience in macro photography, therefore this lens is unsuitable for beginners.

 As far as the lens’ manufacturer in concerned, most people would tell you to purchase a  lens from the same manufacturer as your camera, but this is far from obligatory. Third party manufacturers can also offer you great macro lenses at considerably lower prices.

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