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Macro lenses- choosing and using

Macro lenses- choosing and using


Three Canon macro lenses

Three of Canon's macro lenses: From left to right - 180mm L f3.5, 50mm f2.5, 100mm f2.8.

Macro lenses

I currently own and use the above three Canon macro lenses regularly, so will concentrate on these in this article. However, Canon also makes two others as far as I am aware - the first is a specialist lens called the MP-E 65mm f2.8 1-5X which is manual focus only, but provides focusing between 1x and 5x life size - if you are into seeing what the face of a mosquito looks like - this is the one for you ! You can read more about it here.
** 14th August 2009 update. I have now acquired the MP-E65 and have been using it for some time. I have added a tutorial on this lens here: Using the Canon MP-E65 macro lens

Also there is another excellent Canon macro lens for those who only use the 1.6x crop cameras with the "S" mount called the EFS 60mm f2.8. Beware though, that if you start collecting these "S" lenses and then upgrade your camera to a full-frame or 1.3x sensor camera they will not fit and will become redundant !

In the following article, I will concentrate solely on the three lenses that I own and therefore know intimately.


What makes a lens a macro lens ?

You can get very acceptable results in close-up photography by using an extension tube behind a normal 50mm or short telephoto lens. Before you buy a macro lens, I recommend you try this first.

Although a macro lens can be also be used for general purposes (a 100mm macro makes an excellent portrait lens for example), they tend to be fairly slow to autofocus and are highly corrected for use in close-up work - the use for for which they are specifically designed. If you wanted to make a copy of a rare document, it would be essential that all the text was perfectly sharp from edge-to-edge. A macro lens will do this. If you do a lot of plant, insect or product photography, then you should probably start thinking of getting one of the lenses discussed here.

Macros are capable of focusing much closer than "normal" lenses of the equivalent focal length without adding extension tubes and therefore the subject magnification increases accordingly.

Strictly speaking, macro-photography begins at a magnifications of 1:1 (life size) so unless we start adding extension tubes, bellows or close-up filters to macro lenses, we are really only talking about "close-up" photography here. But this is splitting hairs, these lenses are all capable of getting us in astonishingly close to subjects, which take on surprisingly different and fascinating forms when viewed like this. A common housefly fly or floret of a small flower at 1:1 magnification is still pretty impressive.

Macro photography using modern cameras and flashguns has never been easier, thanks to the advances in through-the-lens (TTL) metering systems which calculate the duration of exposure for the chosen aperture regardless of focusing distance, magnification, or if automatic extension tubes or extenders have been employed. They make exposure simple as they do away with the horribly complicated measurements and calculations that were previously required. Similarly flashguns used with cameras designed for evaluative through-the-lens metering (ETTL) make flash so much easier to manage. Even balancing natural daylight with a touch of fill-in flash has never been easier. Finally, digital cameras enable you to preview the image immediately after taking it, so exposure compensation adjustments can be carried out, or alterations to the positions of flashguns can be made after viewing the result. There has never been a better time to try close-up or macro photography !

The three Canon macro lenses illustrated above, all have their purposes as we shall see. Only one (the 180mm) has been designated the prestigious Canon "L" status, but all three are excellent lenses, being very sharp from edge to edge and all three exhibit good contrast.

The 180mm and 100mm lenses are both capable of achieving a life size (1:1) magnification, but the 50mm can only achieve 0.5:1 and therefore requires the use of a 25mm extension tube to achieve 1:1. The marking on the 50mm lens barrel is confusing, as it appears to indicate 1:1, although this is intended to indicate the magnification only when the tube is fitted.

The price varies widely from the relatively inexpensive 50mm lens up to the very expensive 180mm lens, so when choosing a macro lens, this may be your deciding factor. However, they have different characteristics as summarised in the table below:

50mm
100mm
180mm
Small, compact and light Intermediate Large, bulky and heavy
Cheapest to buy Intermediate Expensive "L" lens
Short working distance - Good if working with restricted space behind you, bad if your subject is unapproachable. Also it can be difficult not to cast your shadow or that of your equipment onto the subject at close range. Intermediate Long focal length lens, so considerable working distance - great for wary subjects such as butterflies and dragonflies.
Close working distance requires lower power from flashguns. This is helpful when working at the usual small apertures, and flashguns can recycle faster. Intermediate Greater distance to subject requires powerful flashguns. The spread of light will tend to light the background more than working in close..
Greater apparent depth of field shows
more of the background in focus. i.e.
harder to blur the background if
required.
Intermediate Easiest to throw the background out of focus thanks to the greater focal length.
Can be used with extension tubes
for greater magnification for greater magnification at the expense of working distance.- Requires 25mm extension tube to achieve 1:1 magnification
1:1 without tubes. Can be used with extension tubes
for greater magnification at the expense of working distance.
1:1 without tubes. Can be
used with extension tubes
for greater magnification at the expense of working distance.
1.4x and 2x teleconverters don't fit - but see workaround in text below Teleconverters don't fit - but see workaround in text below. 1.4x and 2x teleconverters do fit. These further increase working distance and magnification.
No tripod collar available (or necessary) Tripod collar available Comes with essential tripod collar as standard.
Wide field of view Intermediate Narrow field of view
Canon MT24 EX twinflash fits Canon MT24 EX twinflash fits Canon MT24 ex twinflash only fits after purchasing
an adaptor ring.


Let's look at a few of these characteristics in more detail:


1. Effect of focal length on working distance, field-of-view, depth-of-field and magnification.

Here is a poplar hawkmoth on a log in the studio taken at a distance of 80cm (camera back to log) using the 50mm macro. I used an aperture of f22 plus fill-in flash (under-exposed by 1.5 stops) and the camera (Canon 1D mkII) set to Av mode which sets the exposure automatically. As this was around 1 second duration, I used a tripod, remote cable release and set the camera to mirror-lockup in order to reduce the effect of vibration caused by mirror-slap.

Notice that at this distance the subject is very small in the frame, there is a very wide field of view (you can see the room itself) and the depth of field extends back a long way.
50 mm

 

100mm
This is the shot taken in exactly the same way with the 100mm macro at the same 80cm working distance.

It is pretty apparent that the field of view has reduced drastically, as has the depth of field - the plant behind has now become the background, but it is still possible to make out that it is a weeping fig! The moth itself is much bigger in the frame - i.e. the magnification has increased at the same working distance.

 

Finally, here is the same shot taken with the 180mm macro at the same 80cm working distance.

The field of view is narrower still, the magnification is greater and the depth of field has reduced so that the background is now highly blurred. This shot could now pass for having been taken outdoors in the wild!
180 mm


There are times when the greater depth-of-field of the 50mm lens would be beneficial, but in this example, the 180mm lens is the most useful. If the shot had been taken in the field, and the moth had been less tolerant of my presence, the 180mm lens may have got me the shot whereas the much closer approach required by the other lenses may have frightened the insect away.

When photographing a static subject such as a plant in close-up, the need for such working distance may be unnecessary. In fact if you had a tree, wall or cliff-edge behind you, this may prevent you getting far enough away from your subject. I sometimes work with a perspex shelter when photographing plants with available light, and it would be totally impractical to work as far away as the 180mm lens would demand.

When out photographing birds with long telephoto equipment, I sometimes stick a small 50mm macro in my pocket - just in case I see some exceptional insect or plant. Its small size and negligible weight means that I can still take a macro with me - just in case.


2. Control of background using different focal lengths

This time, I moved the camera closer to the subject with the 50mm macro until the moth was about the same size in the frame (magnification) as the previous 180mm macro image - which you will remember was shot at 80cm distance. To achieve this, the working distance had to reduced to about 28cm.

Notice how moving closer to the subject causes the depth-of-field to reduce - that is, the background is far more blurred than at 80cm. Having said that - the background is still only partly blurred. This is not necessarily a bad thing - there are times when it may be your aim is to show the subject in it's natural habitat for example. On the other hand, if the background is ugly or distracting, the longer focal length of the other two lenses may be preferable to through it out of focus.

Finally, although hard to judge here on this small image - notice how the image quality is still excellent - despite this being a cheap non- L lens ?

50mm at 28 cm

50mm macro at 28 cm

Here are the other two macro lenses at about the same magnification - watch the control over background that the lenses enable:

100mm macro at 50cm
180mm macro at 80 cm
100mm macro at 50cm
180mm macro at 80 cm


Image quality comparison

A good way of testing lens quality is with a banknote. This is a 100% unsharpened crop of part of a five pound note. I moved the note backwards and forwards until half the note's width filled the viewfinder.

The test was conducted indoors using a desk lamp as the light source, camera was a Canon ID mk II, ISO 200 and an aperture of f8 selected in AV mode. The camera was mounted on a Gitzo tripod and I used a cable release and mirror lockup. Distances quoted are from the back of the camera to the note ( NB not from the front of the lens). The raw image was converted in Photoshop ACR using "auto" settings. Once in Photoshop, I applied auto levels and auto colour, then reduced to 590 pixels wide using Bicubic sharper interpolation for web viewing.

I took the images in triplicate and chose the best image of the three (although the differences were pretty negligible). Here are the results:

Starting image

The rectangle marks the area of the 100% crops

Starting image

50mm macro at 25 cm distance

100mm macro at 42 cm distance

100mm macro at 42 cm distance

180mm macro at 73 cm distance

180mm macro at 73 cm distance

Conclusions

There is negligible image quality difference between the three lenses when tested in this way. Remember, these are 100% crops of unsharpened images - any differences seen are probably only due to RAW conversion and scaling for web viewing. One might expect the 180mm L lens to out-perform the other non L-lenses, but this does not appear to be the case. What is more of an achievement perhaps, is the fact that the 180mm lens can still produce the same quality as the other lenses when viewed at the same magnification - but at a much greater shooting distance

 

Using extension tubes/bellows and tele-extenders.

Canon 25mm extension tube
Canon 25mm extension tube

All three macro lenses accept an extension tube or stack of tubes. Extension tubes contains no optical elements, and are available in different lengths. The effect of the tube is to enable the lens to focus closer than it did previously as it is effectively now mounted further from the camera body. In other words, by enabling you to get closer to the subject, the magnification will increase (and depth of field will decrease proportionally.)
In fact, an extension tube can be used to increase magnification by reducing working distance on any lens - it just won't now focus to infinity. Bird photographers sometimes use a tube between a super-telephoto lens and the camera to enable them to get closer to an accommodating bird than the minimum focusing distance of the lens will normally allow. This is how a really close head-shot can be made with a long lens. Before investing in a macro lens, it might be worth trying an extension tube behind a normal 50mm lens or short telephoto if you happen to own one.

With an extension tube you are sacrificing working distance for gains in magnification. One downside is that light has a longer path to make down through the lens and then through the extension tube to the film or image sensor of the camera. The extension tube therefore robs you of a stop or more of light, depending on which length tube you opt for.

Modern automatic extension tubes initially appear expensive considering they contain no optics, but they do have to be fitted with all the electrical contacts necessary to pass information between the lens and the camera. Before automatic tubes were available, through- the-lens metering was not possible and exposure allowances had to be made for the presence of the tube.

I once had a bad experience with a cheap set of tubes, which caused intermittent flare as they had not been adequately protected against internal reflection. Since that time I have only used the manufacturers own tube (I only currently own a Canon 25mm tube).

Bellows and focusing rails are specialist equipment for those requiring magnifications far beyond life size. They consist of a light-proof set of corrugated bellows which are fitted between the lens and the camera. The lens can be moved backwards and forwards on the bellows rail - effectively becoming a huge and infinitely adjustable extension tube - with the accompanying huge loss of light. Their use tends to be restricted to the studio where sufficient light and control of vibration at such high magnification is easier to control than in the field.

One other use of an extension tube.

The next section deals with tele-extenders. Unfortunately Canon's 1.4x and 2x extenders are only designed to work with the "L" lenses, so physically don't fit the 50mm and 100mm macro - which is a shame. However, all is not lost, as there is a workaround - simply fit a short extension tube between the lens and the extender.

Tele-extenders

The Canon 2x Extender
The Canon 2x Extender

Tele extenders are far more familiar to bird or wildlife photographers using telephoto lenses than those interested in close-up photography. They extend the focal length of the lens - so a 500mm f4 lens becomes a 1000mm f8 when fitted with a 2x extender for example.

Extenders used to have a bad reputation for image quality, but the latest manufacturers-own extenders are optically matched to the lenses they are intended for and provide superb quality. An extender has glass elements inside it that effectively magnify whatever is in front of it by a factor of 1.4x or 2x depending on which extender is in use. They will also multiply lens defects - so should only be used with the finest prime lenses for optimal results.

So how is this of use to close-up photography ?

Put a 1.4x converter behind a 180mm/f3.5 macro lens for example, and you will have a 252 mm f5 lens with a 1.4 greater magnification and working distance. This (in combination with a monopod) is one of my favourite combinations for photographing butterflies on a sunny day, when the one stop light-loss penalty inflicted is less of an issue than getting close to hyperactive insects. A 2x converter will make the 180mm lens effectively 360mm but will rob 2 stops of light. If you set the lens to 1:1 and move in closer until focus is achieved, you will be working a 2:1 or twice life size.

As previously mentioned, by fitting an extension tube between a 50mm or 100mm lens and the extender, it can be physically made to fit. Unless the subject and camera is totally static, it is more practical to use flash as the sole light source when using such a set-up. Here is an uncropped image taken with this combination. The quality of the image is still extremely high, despite the insertion of two items between the lens and the camera:

Elelephant hawk-moth

Image of an elephant hawk moth taken with 100mm macro plus 25mm
extension tube plus a 2x extender between the tube and the camera

Image quality comparisons of the 180mm lens with extenders.

Here is the starting image again, taken with the bare 180mm macro. This viewfinder image size was used as the basis for matching the other images taken when converters were added. By varying the distance of the banknote to the camera, approximately the same magnification was achieved in each case. The rectangle represents the magnified area in the unsharpened 100% crops that follow

Starting image

starting image

180mm lens, no extender at 73cm distance. 100% crop

180 mm, no extenders

180mm lens, Canon 1.4x mk II extender at 88cm distance. 100% crop

180mm lens, Canon 1.4x mk II extender at 88cm distance. 100% crop

180mm lens, canon 2x converter mk II at 118cm distance. 100% crop.

180 mm lens, 2x converter

Conclusions from these tests:

The 1.4x extender shows negligible image degradation.
The 2x extender shows some degradation when the bank note image is matched for size in the viewfinder. Not a bad result considering that this is a 100% crop of the image and the image is not sharpened.

However, it gets a lot better for the 2x converter yet, as this test does not really show the results of how it would be used in the field with a flighty subject such as a dragonfly - which is very hard to approach without scaring it off. This is where the benefit of the extra focal length pays off. Here are the un cropped images from the same shooting distance (73cm) :

180mm macro - no converter at 73cm working distance

180mm macro - no converter at 73cm working distance



180mm macro plus 1.4x converter (equivalent to focal length of 252 mm) at 73cm working distance

180mm macro plus 1.4x converter (equivalent to focal length of 252 mm) at 73cm working distance

180mm macro plus 2x converter (equivalent to focal length of 360mm) at 73cm working distance

180mm macro plus 2x


The 2x converter now looks far more impressive !

Finally here is a real world image of a rare Wood white butterfly taken with the 180mm macro plus 2x converter. Exposure: 1/100 sec f7.1 ISO 250 (Evaluative metering + 1 exposure compensation). Notice how the background bokeh is perfectly smooth despite nearby grass stems behind the subject- that is thanks to the 360mm combined focal length. The depth of field was so tiny, that it was imperative to get the camera exactly into the plane of the insect's wings.

Wood white

Which macro lens should I buy ?

In this article, I have tried to illustrate that there is no one macro lens that does it all - they are horses for courses:

If you on a strict budget or only rarely dabble in macro work, or want to travel light, do copy or product work in a studio at close range - then the 50mm macro lens is the one for you - it is a real bargain.

If you are interested in photographing dragonflies or butterflies that are very flighty, then a 180mm macro (possibly even fitted with an extender for even greater working distance) is a huge advantage. You will also have the ability to blur backgrounds considerably with this lens, but you will need deep pockets - this is an expensive lens. The Sigma 150mm and 180mm macros have a very devout following also as they are of very high optical quality and are cheaper than the manufacturer's own.

Then there is the 100mm macro. I haven't mentioned it so much in this article, as the other two lenses represent the extremes and better illustrate the points I have been trying to make. However, my recommendation would be that if you only wish to own one macro lens, then this is the one to buy. It is the best compromise between price, size, weight, working distance etc. Although not designated "L" status, the image quality is as good as the L lens in my opinion. When working with flash, you feel to be at a sensible working distance from your subject, and you are not normally working so close that you are casting shadows over your subject by the equipment itself.

If you are interested in photographing plants, then the 100mm macro is an ideal lens. The 180mm only beats it when you are trying to isolate the plant from a highly distracting background.
For many years, I only owned the 100mm macro and only added the other two as the icing on the cake as funds permitted. In reality I could still get by with just this lens if I had to. My lens is the old pre-USM motor lens. The latest version has internal focusing, is much quicker and quieter to autofocus but has similar optical quality I believe. As I almost always focus manually in close-up I don't consider this to be much of a hardship so haven't yet felt the need to upgrade.

Although I have no experience of them, there are the two other macros that I mentioned at the beginning of this article:
The MP-E 65mm f2.8 1-5X Macro Lens for ultra close-up by experienced users only I would suggest. The EFS 60mm f2.8 which only fits the 1.6x cameras with the "S" mount. You will also need to ensure, that if you are buying an extension tube for this lens, it must also be the latest "S" version.

I should also mention again that Tamron and Sigma make some optically excellent macro lenses that may be worth investigating as they may provide equivalent quality to the manufacturer's own at a lower price.

Do I need to use a tripod with these lenses?

Working at high magnification demands excellent technique if sharp images are to be obtained.If you are using flash as the sole light source, then theoretically you do not need a tripod as the flash duration is so short (around 1/50,000th of a second). There is no chance of camera shake at this speed and unless you are photographing something extraordinarily rapid, subject movement is not an issue either. However, I still use a tripod whenever possible, even when using flash, as the depth of field is so minute, that it is very difficult not to have swayed/moved in or out a little in the time it takes to press the shutter.The easiest way of photographing in close up with modern TTL/ETTL flash is to set the camera to manual, set the aperture to f22 for good depth of field and the shutterspeed to the maximum flash/camera synch speed (typically 1/125th - 1/250th sec) and shoot away.

If you are using natural daylight or daylight plus fill-in flash for your close-up work, then I recommend setting the camera to aperture priority (AV mode), start at f22 and see what shutterspeed the camera wants to set. Even in bright light, it will be a very slow setting, so a sturdy tripod (or monopod if a tripod is impractical) becomes essential. If the shutterspeed is around 1/10th to 1 second, then I would use a remote cable release (to prevent transmitting vibration to the camera as the shutter is depressed). I also routinely use mirror-lock up at these speeds as the vibration of the camera's mirror slapping around is sufficient to soften images a little.
Also remember, that if you are using flash as a fill-in, it is only being used to reduce shadows, not light the subject - so don't rely on the flash freezing movement - it won't - as the slow shutterspeed that the camera will select will enable a bucket load of camera shake to occur regardless !