Macrophotography explained in eight questions
Macrophotography is not a complex thing, but there are a few points that need to be clarified in order to enjoy it. If only to take a look at the equipment used for macro photography, how close you can get with a dedicated lens, depth of field (which is practically non-existent!) and focusing (which can only be done manually). Let's get started?
What equipment do I need for macrophotography?
In fact, there are four ways of doing macro photography. One: you can use close-up lenses, which are filters that stack up on the front of any lens and allow close focusing. But they have one drawback: the quality of the final image is not very good. Two: there are also "extension rings", which are inserted between the camera and the lens. Here, there is no loss of quality, but the loss of light is major. Three: you can also buy an "inversion ring", which mounts the lens backwards on the body. But there's nothing ideal about this: diaphragm control becomes inaccessible. These three methods are just stop-gap measures. If you want to take macrophotography seriously, nothing beats a lens dedicated to the task.
What is the 1:1 ratio?
When a lens designed for macro photography is set at its closest setting, the image formed on the image sensor is the same size as the subject. If, for example, you have a camera with a full frame image sensor (its surface area is therefore 24 x 36mm), at the 1:1 ratio, the subject you are framing will also be this size: 24 x 36mm. The image of the subject formed on the sensor is therefore its "real size". If you immortalise a ladybird that is one centimetre long, the image of it projected onto the sensor will also be one centimetre long.
Do all macro lenses offer the 1:1 ratio?
Unfortunately not. Some lenses are limited to a 1:2 ratio, which means that the image created would have to be enlarged twice to obtain that of a 1:1 lens. However, an image taken at a ratio of 1:2 is still considered macrophotography. At 1:3 and 1:4, the term "proxiphotography" is used. Beyond that, it's simply a "close-up"
So 50mm, 105mm and 180mm macro lenses, set at a 1:1 ratio, will produce the same image?
Yes, but not at the same distance. A 50mm macro lens, set at a ratio of 1:1, will need to be placed 20cm away from the subject for it to focus correctly (this distance is calculated from where the sensor is located in the body to the subject). To take the same image, a 105mm lens would be installed 30cm away, which is very practical: the insect will probably remain in place, and there is less risk of casting a shadow if the light comes from behind you. With a 180mm lens, the image will be taken at a distance of 50cm; this seems ideal, but the lens becomes large, heavy and expensive. The most recommended focal lengths for macrophotography are around 90mm, 100mm and 105mm.
Why is there practically no depth of field in macrophotography?
In fact, it's part of the immutable laws of optical physics: the closer you focus from the sensor, the shallower the depth of field - and there's not much you can do about that. At the 1:1 ratio, when the aperture is fully open (f/2.8), the depth of field is barely 0.7mm. When the aperture is closed to f/32, the depth of field increases from 0.7mm to 8mm, which is not much of a gain given the loss of light (256 times less luminosity!) You have to learn to accept the near absence of depth of field.
If the vast majority of 105mm macro lenses can achieve a 1:1 ratio and therefore create the same image, why are macro lenses available at $250, $800 and $1,600?
For the same reason that cars cost $8,000, $20,000 and $80,000: the quality of the construction, the features, but above all: the quality of the optics. We're talking here about the precision of the details, the definition of the textures, their uniformity throughout the field (from the centre to the edge of the image), the accuracy of the colours in the image and the overall contrast. This depends on the type of glass, the multi-coating applied, the optical formula used, etc. The quality of a lens (and its price) is directly linked to all these factors.
I've been trying out a macro lens recently, and I've run into a nasty problem: the autofocus keeps slipping back and forth, never stopping! Impossible to take an image!
Remember that the closer the focus is to the sensor, the less depth of field there is. At the time of shooting, the diaphragm is fully open (f/2.8), so the depth of field is practically non-existent: 0.7mm. The camera tries to focus with a very shallow depth of field (it's a bit like groping in the dark), on a very large subject that sometimes moves (a flower with a bit of wind), while the photographer, camera in hand, is rather unstable. It's practically doomed to failure. That's why we always focus manually in photomacrography – but not the way you think!
First, focus the lens manually ("MF" or "M"). Then, using the focus ring, you set the ratio you want to use (for example: "1:1"). We know from earlier that if the lens is set to 1:1, the camera needs to be 30cm from the subject. So, with your eye on the viewfinder, you get close to what you're trying to photograph, and when it's precise (so you're at the right distance), you press the shutter release. That's all there is to it! We call this "body focusing", i.e. it's done by moving your body.
This "body focusing" method is pretty difficult to do when you're on a tripod!
Yes, it is. That's why there's a brilliant accessory that allows you to achieve the same forward-backward movement when the camera is on a tripod: it's called a macro focusing rail.
Macrophotography allows us to see a wealth of detail that is barely discernible to the human eye. That's why these images are so impressive! Once you've mastered the technical side – understanding ratios, optimising settings, controlling depth of field and using body focusing – all that's left to do is create. The freedom is yours.
In-store courses are available at Collège Gosselin (private, group and even outdoor photo workshops!) for those who want to deepen their knowledge. Don't forget to bring your camera and a fully charged battery! It could come in handy...
 | Jean-Francois Landry Jean-François Landry is a versatile photographer who is particularly passionate about urban macrophotography. He has been working at Gosselin Photo Vidéo in Quebec City as a trainer and advisor for more than twenty years, where hundreds of enthusiasts have benefited from his expertise, as well as from his knowledge of the subject. |
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