Macro photography is generally regarded as covering a range of degrees of close-up work from say half-lifesize (1:2) through to 5 times life size (5:1). This is equivalent to an object of length 7cm (1:2) to 7mm (5:1) filling the full width of a 35mm frame. Beyond this one is really in the realms of photomicrography (taking pictures through a microscope).
Many tele-zoom and standard zoom lenses are marked “macro” but don’t actually go smaller than about 1:4 or 1:3 and so cannot be regarded as real macro lenses. The main aspects of macro work are:
- Specialist equipment is required which may range from simple add-on (supplementary) lenses through to expensive, specialized macro lenses
- Depth of field is very small (and gets smaller the more the subject is magnified)
- If flash lighting is used then there are specific considerations for macro
- A stout tripod is nearly essential (and certainly essential for available light photography)
Equipment
In order to get a macro image one needs to be able to focus much closer than a lens will normally focus. The main ways for achieving this are:
- A supplementary lens attached to the front of your normal lens
- Allowing your lens to move much further away from the camera body by using extension tubes or a bellows unit between the camera and the lens
- Using a specialized macro lens that enables very close focusing
These options are ranked in order of cost (cheapest first) or inversely according to quality (highest quality last).
There is a fourth method, that is cheap and gives good image quality: mounting your normal lens in reverse on the camera body using a special adapter. Unfortunately this is difficult on some modern camera bodies that require electronic connections between the camera body and the lens. For Canon EOS cameras this can only really be done through the Novoflex reverse adapter which maintains the electrical connections between the lens and body, but is a relatively expensive solution.
Canon sell a comprehensive range of macro photography equipment.
Supplementary Lens
Supplementary (”close-up”) lenses are normally simple, filter like, lenses that screw onto the front of your normal lens. They typically come in different strengths – 1 diopter, 2 diopter, 3 diopter and 4 diopter corresponding to a focus distance of 1 meter, 0.5 meter, 0.33 meter and 0.25 meter respectively (when the main lens is focused at infinity).
When the main lens is focused at its closest normal focus point these distances are somewhat reduced. Maximum magnification depends upon the focal length of the lens in use.
These close-ups lenses may be a single piece of glass or a compound lens (typically an achromatic doublet) which gives better image quality but at greater cost.
The ultimate supplementary lens is a standard prime lens (especially a 50mm lens) mounted (in reverse) on the end of your normal lens. The prime lens acts as a highly corrected, compound supplementary lens. All that is required is a simple adapter that screws into the filter thread of each lens in order to join them together. The diaphragm of the reversed lens is kept fully open so it doesn’t matter what sort of lens it is – it doesn’t have to be the same fitting as your normal lens – it’s a great use for an old manual 50mm standard lens that you may have or which can be bought for less than $20. A big advantage of all supplementary lenses is that they do not affect the effective aperture of the main lens.
Extension Tubes
Extension tubes are in many ways the most cost effective and usable way to get macro photographs without a specialised macro lens. They are simply hollow tubes that fit between the lens and the camera and effectively behave as though the focus operation of the lens was able to rack the lens out much farther than normal. The tubes usually come in sets of two or three that can be combined to give greater degrees of magnification.
Because there is no glass in the extension tubes they do not degrade image quality, although you should be aware that you are using your lens beyond its designed limits and so various optical aberrations may occur – but these are not typically critical for the average user.
The extension tubes normally also transfer the connections (electrical in the case of EOS cameras) between the lens and the body which means that the automatic diaphragm and TTL metering all work as normally. Autofocus will usually also continue to work, but in practice is more of a hindrance than a help with macro photography.
While the obvious place to stick an extension tube is behind a standard (50mm) lens to get a good macro effect they can also be used behind zooms or telephoto primes. An extension tube behind my 200mm f2.8 lens gives me a great near macro set up for situations where I cannot approach very close to the subject.
Extension tubes suffer from the basic rules of optics about shallow depth of field and smaller effective apertures.
Bellows
Here is a photograph of a
Bellows work like extension tubes but with a continuously variable extension. For Canon EOS SLR’s the only bellows that works is a third party bellows made by Novoflex and very expensive! Bellows, like extension tubes, suffer from the basic rules of optics about shallow depth of field and smaller effective apertures.
Macro Lenses
Macro lenses are generally expensive but provide the ultimate solution to macro photography. They generally provide all the facilities one expects in a lens – including automatic aperture and even auto-focus, but the latter is pretty well useless when doing macro photography.
Handling is simpler than the other methods and they usually provide the flexibility the go from focus at infinity all the way down to 1:1 in a continuous manner. Some lenses such as the Canon EF 50mm f3.5 Macro only go to 1:2 and require supplementary lenses or adapters to go all the way to 1:1.
The Canon 65mm MPE lens is an exception in that the farthest away it will focus is a few inches giving a 1:1 image but it then enables one to focus down to five times lifesize – i.e. 5:1. This lens looks innocent enough when in its normal position (1:1) but is a monster when racked fully out.
While macro lens are specially corrected for aberrations that arise at close focusing distances they do not change the basic rules of optics about shallow depth of field and smaller effective apertures.
Effective Apertures
As a lens is extended (by focusing or by use of extension tubes or bellows) the ratio between the circle of the aperture and the length of the lens gets smaller. Your f2.8 lens starts to become an f4 and then an f5.6 lens as you focus closer and closer. What is worse is that at say f16, which you have chosen to get the depth of field you need, the lens is actually at an effective f32. In the old days you had to manually calculate this effect (and still need to today if using a flash that doesn’t have TTL control) but with TTL metering the camera automatically allows for this. But one still has the problem that a very small effective aperture is being used so exposure times will be correspondingly longer.
There can also be a problem with viewfinder brightness at extreme magnification. My Canon MPE lens, for example, has a maximum effective aperture, when shooting at 5 times lifesize, of f16.
Use of Multipliers / Tele-Converters
It is perfectly possible to put a 1.4x or 2x tele-converter behind extension tubes, bellows or a macro lens to increase the magnification. If you put a 2x convector behind a macro lens that goes to 1:1 then magically you have the ability to go to twice life size. Remember though that you will lose two more stops on top of the already reduced effective aperture.
Tip: if you are using a Canon EOS 100mm macro lens then normally you cannot put Canon’s 2x or 1.4x converters behind it because the Canon converters only work with longer focal length “L” lenses. Don’t despair: simply put a small extension tube – e.g. 12mm – between the lens and the convertor and it all fits and works brilliantly. (Independent maker’s converters can also be used but possibly with some loss of quality).
Flash for Macro
When using flash for macro shots you typically cannot use a built in flash since the lens will block out most of the light from the subject. You need to use an external flash gun, preferably connected via a connecting cord to the camera (either to the hot shoe or a PC flash connector)
Ideally an external flash will be mounted on a bracket that enables you to position it close to the subject. Since TTL flash makes life much simpler it is worth using a connection cord that preserves the TTL functions of the flash. For my Canon’s this is either the Off-Camera-Shoe-Adapter or the Off-Camera-TTL-Adapter.
Ring flash
An alternative to a conventional flash gun is the Ring Light or Ring Flash (such as the Macro Ring Lite MR-14EX) which is a circular flash unit that mounts directly onto the end of the lens.
This has the advantage of getting it close to the subject and unobstructed by the lens. Ring flashes do not, typically, have a high output but this in not normally a problem since they are used so close to the subject.They do give fairly flat lighting (although on some flashes you can vary the intensity from each half of the flash) which works fine for most subjects but is not always ideal. However, they are so convenient to use that this is my normal way of taking macro shots.
Flash exposure
OK, so TTL flash means you don’t have to worry about the flash exposure for macro. Well not quite true. For some reason that I haven’t been able to get to the bottom of every camera I have used with TTL flash and a macro lens seems to benefit from about 1 stop extra exposure (either adjust the ASA rating [film cameras only] or use flash exposure compensation if you camera supports it). Also remember that with macro a small object may fill the frame with a single colour so additional compensation may be needed for a very light subject (an extra 0.5 or 1 stop) or very dark subject (say 1 stop reduction)
Focusing Stage
The normal method of getting a subject in focus during macro work is to adjust the lens to the approximate focus point and then move the camera / lens backwards and forwards to achieve optimum focus. This is a real pain if the camera is on a tripod! The answer is a macro-focusing stage: this holds the camera and itself is mounted onto the tripod. Knobs then allow you to move the camera/lens smoothly forwards and backwards and also from side to side.
Techniques
Technique for macro shots is dominated by the need for depth of field. There are a number of things you can do to reduce this problem:
Use a small aperture – normally I use f16 since below this you can start to get image degradation due to diffraction. Try to position the key parts of the subject that you want in focus in a plane parallel to the plane of the camera (i.e. keep all the bits of the image the same distance from the camera). Where the subject doesn’t lend itself to this approach you just have to decide which bit you want in focus. Use a tripod and focusing stage to allow you to accurately position the camera/lens relative to the subject
If possible (it’s not essential but it helps) use an angle finder / magnifier on your camera’s eyepiece since this can make critical focusing easier.
With natural light photography you will find that the long exposures cause problems of vibration. Hence the need for a sturdy tripod. Mirror vibration can also have an effect which can be reduced by using mirror lock-up if your camera supports it. For outdoor shots I have found the biggest problem is movement caused by even a slight wind. For this reason I often shoot with flash even outdoors. If the subject doesn’t suit flash you just have shield the subject as much as possible from the wind and be patient!
The use of flash with macro shots tends to give a specific type of image with the main subject well illuminated but with the background very dark or black. This arises because of the huge relative difference in distance of the flash from the subject and the background. For some subjects this works well but for others it is less than satisfactory. Multiple flash can help in this situation but requires considerable set up to get the effect right.
It is possible to do hand held macro work if you are using a flash. The problem is not camera shake – since the flash has a very short duration – but rather holding the camera such that the subject is in focus at the point in time you press the shutter release button. Even autofocus won’t help here since it locks on the half depression of the shutter button which allows plenty of time for you to slightly move the camera and end up with the subject out of focus. My only advice here is keep it stopped down to f16 or even f22 (ignore my advice earlier) to give you the best chance of staying within the depth of field and then to take lots of shots so that at least some are in focus.
Any suggestions, ideas? Feel free to comment on this article!
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