What should i look for in a macro lens?

Answer 1

There are several issues associated with macro photography. These include adequate light, good depth of field and magnification. There is also the question of exactly what kinds of subjects you want to photograph. I’ll touch on each of these as we look at macro lens characteristics.

Starting with magnification, since that’s the whole purpose of macro photography, the current crop of macro lenses offer a 1:1 ratio. This means that the image on the sensor is exactly the same size as the subject. If you’re after something really small, a lady bug for instance, you definitely want a 1:1 ratio otherwise your bug isn’t going to be particularly large in your finished picture. On the other hand if your typical subject is flowers that are twice the size of your sensor or larger, a 1:2 (half life size) ratio would be more than adequate for you. So the first decision you need to make is how much magnification you need. I’ll talk about going higher than 1:1 later too.

Now, macro lenses come in different focal lengths. They often start around 50 mm and can extend to 200 mm usually. What’s the difference? The higher you want to magnify, the closer you have to get to your subject. If you’re doing a lady bug at 1:1 a 50 mm lens will require you to be usually within about four inches of your subject. That can create problems. Being that close you could spook the bug for one thing. You could also end up casting a shadow on the bug thereby demanding a slower exposure that will risk camera shake or a blurry subject as it moves on its own. Selecting a 100 mm lens your distance changes to about a foot which is more practical. Subject to lens distance is also crucial from a different point of view. You can’t always get close to the subject because of physical barriers like a swamp or something. In those moments you also want to have a better working distance.

So the next issue to decide is how far you’re willing to go to get your picture. If very close isn’t an issue for your kind of subjects, a 50 mm lens may do. If it is an issue, think 100 mm or 200 mm.

That said though, there is now an exposure issue. In this kind of work there is never enough light and it’s a real challenge sometimes to focus properly. As a result it’s desirable to have a fast lens, something like f2.8 or faster. Unfortunately as your focal length increases, your maximum aperture (and thus lens speed) decreases leaving you with less light. So you have to decide how important a large aperture is to you compared to the focal length you feel you need.

At the same time though, another issue is depth of field. As you magnify your subject, your depth of field drops dramatically. It’s not unusual to get the head of your little bug sharp while the rest of the body ends up out of focus. To deal with this issue you have to stop your lens down as much as possible. Many macro lenses tend to excel at this in that they usually stop down to f32 or more which gives you a better shot at a good depth of field. Of course when you stop the lens way down, you’re going to have to go for longer exposures which also doesn’t always work with a little bug since they rarely ever sit still. You can work around that by increasing your ISO however I’d suggest stopping at around 400. Higher than that and you’re risking noise.

So you want to look at the minimum aperture on the lens you’re considering too. The smaller it goes the better your odds for getting your entire subject sharp.

Modern macro lenses can also be had with auto focus and with an image stabilizer. I have a Nikon 105 mm macro that has both that I use on a Nikon D200. The auto focus is nice but if you work at 1:1 it’s also useless. The way you focus at those magnifications or higher ones, is to set the lens to manual focus and to set the focus to minimum. Then you simply move the camera in and out until your image is sharp. There is no other way to achieve 1:1 or higher ratios. The only time when your auto focus is a neat feature is if you are working at a lower ratio that allows you to get back further from your subject.

The image stabilizer on the other hand is worth its weight in gold. In the past the only way to do macro work was to use a tripod. With an image stabilizer you can often work hand held and still get crisp images. Personally I’d insist on this feature even though in my film days I got along ok without it.

So those are the things to consider, the focal length (determines your subject to lens distance), the magnification 1:2 to 1:1, the minimum and maximum aperture, whether it has an image stabilizer, and whether you want or need auto focus.

My choice was the Nikon 105 mm macro. It’s reasonably fast (f2.8) it stops way down for good depth of field (f32), it’s not too heavy, it allows me a reasonable lens to subject distance and it has an image stabilizer. But then there are many other lenses with similar characteristics.

Now if you want to magnify even more, you can get extension tubes. These are hollow tubes that go between the macro lens and your camera. The longer the extension, the more you will magnify your image. How much you magnify depends on the focal length of the lens and the length of the tube. A 50 mm lens coupled with a 50 mm extension tube will give you a 2:1 ratio, basically twice life size. While that sounds exciting, that means you will be even closer to your subject and you will have even less light to work with. Add to this, your depth of field will also be dramatically less again. So the message there is that the more you magnify the more challenging it is to get your picture. I’ve worked to magnifications up to 8x and at that level I’m usually a quarter inch from my subject, what I see in the view finder when I stop down is almost total blackness and I’m doing sixty second exposures at high noon.

Now when you do go into higher magnifications, especially with extension tubes, it becomes impossible to hand hold the camera in any reliable way and still get a sharp picture. Tripods become crucial at this point. But this introduces the problem of how to move the camera back and forth to get that crucial focus. You can mess around and achieve sharp focus this way but chances are your subject may be gone by the time you’re finally set up. So there is another gadget you might consider, a focussing rail. This is a platform that sits on the tripod and the camera sits on top of it. It has a dial that moves the camera back and forth and it has a release that allows you to make large movements first so that the dial only needs to be used for the final adjustment. This becomes a really vital focusing tool if you start to use extension tubes.

I would add as well that when you first get into this kind of work it can be very frustrating. It’s not only a lens issue and a depth of field and exposure issue, you also have to move to spot metering quite often to get just your subject perfectly exposed. And of course once you’re into things like bugs you’ll take a lot of pictures of air as the bug takes off while you’re trying to get focussed. However … these issues aren’t impossible, they simply take a lot of patience and practice and if you invest that, macro photography can be incredibly rewarding. I’ve been doing it for thirty five years.

One other thing about macro lenses you should know about is that they do not focus like most lenses. Most lenses are designed to focus on an arc because that’s how we tend to see. Macro lenses are designed to focus on a flat plain. What that means is that while the macro is ideal for little things, it’s not ideal for scenery. However, in addition to photographing little things perfectly, they are also the lenses of choice if you are taking a picture of a flat object like a painting. The macro lens will give you a crisp image of the entire painting corner to corner.

I hope that helps you a little.

Answer 2

1) magnification factor. Generally a lens that can do 1:1 is a true macro lens. That is, the object will be the same physical size on the sensor as in real life. However, even a 1:2 macro can be quite spectacular on a digital SLR.

2) working distance. How far from your subject can you be to take your macro shot. Note that working distances are measured from the plane of the sensor to the subject, not from the front of the lens to the subject. There should be a marking on your camera something like this: --o-- to indicate where the plane of the sensor is. Usually the marking is just to the right of the pentaprism on the top of the camera, towards the rear. Working distance is important because a) too close can scare critters like bugs and b) it can affect how you get light onto the subject.

3) focal length. Generally this also affects working distance. A macro in the 90mm to 105mm range usually provide a reasonable working distance for most objects, but the 180mm to 200 range really gives you some room. In the 50mm to 60mm range, it's too close for most bugs, but excellent for static objects like coins and flowers.

4) focusing. Auto focus isn't as critical in macro, because manual focusing is much more important. The depth of field is very shallow, so you'll want to manually focus on the area of interest.

5) wide aperture. This helps you to manually focus by making the view through the viewfinder brighter. But you'll stop down to like f/16 to increase depth of field in a macro.

6) mount. Make sure it fits and will allow you to use the wide aperture. Modern lenses are automatic aperture--wide for composing, and they stop down automatically for exposure. Older lenses may not be automatic aperture and will stop down as you turn the aperture ring, making the view darker.

7) last thing to worry about: cost. Too cheap and you'll get bad results.

Answer 3

Buy the one designed for your camera by the manufacturer of your camera.

You usually have a choice between 50mm and 100mm. I personally prefer the 100mm focal length because it gives a better working distance from bees and butterflies. It also helps prevent some lighting problems, since with a 50mm you may get close enough to cast a shadow or otherwise interfere with the light.

Answer 4

Depends on a lot of factors. What kind of things will you be taking pictures of? How much magnification do you need? Don't skimp on the brands, get high quality ones otherwise you will pay for it. They are expensive though, I have a set of Tiffen that I love. Good luck!