Macro Photography is about capturing life from up close which does not necessary mean your lens is centimetres away from your subject. Some zoom Macro lenses will only focus at 1m or even 1.5m away. Macro Photography is a world of its own and one only needs to search the web to realise the limitless diversity of subjects: from plants to the tinniest insects without forgetting all the interesting patterns and textures one can find in and on the most common object and places. However, this world can be very costly as the lens are quite expensive from £300 and while the subjects are diverse the use of such lens is very specific and not so versatile. Although Macro lenses can be great for Portraiture. It is one thing to appreciate a Macro photograph, but it is another to enjoy capturing it. I for one am yet to like it. So how do you know whether you like one thing before you have it? While you could always rent a Macro lens for a week end, you are soon to realise that a week end might not be enough to get things right. Here is my suggestion to you for a cheap approach: Extension Tubes.
What are Extension Tubes?Extension tubes are just rings that are placed between any lens (wide angle, nifty fifty, telephoto, prim or zoom) and your SLR. There is no glass element in the rings. They only act as separators.
How do they work?Have you noticed that the closer your lens get to the subject, the bigger your subject appears? This is what is behind zoom lenses (more or less). There is one problem, though. You cannot get as close as you wish to a subject hoping to get it bigger indefinitely. Well, that is obvious you may say but not quite for a reason you may be thinking. Every lens has a minimal focussing distance which is the closest distance your Camera sensor (or film) can be from a subject for your lens to focus. Very often you can see it written on your lens barrel (i.e. 0.45m). What the Extension Tubes enable you to do is keeping your sensor away from the subject according to your lens minimal focussing distance restriction, while having your lens closer to your subject. There is nothing more to it. Here are two samples of exposures taken without and with the Extension Tubes:
How cheap is that alternative?Well, you can find them for about £50.
Are they comparable to a real Macro lens regarding result they achieve?Honestly no! A real Macro lens is a one that offers you a magnification ratio of 1:1. What this means (contrary to what I said in the video!) is that if your subject measures 1 cm, it will represent 1 cm on the sensor (and not in the final image since your image is much bigger than the size of your sensor thanks Lord for that!). One can find many Telephoto lenses that claim to offer Macro capability, but when looking at the ratio closely you will see you will get 1:4, 1:3 or 1:2 but rarely 1:1 unless it is a real Macro lens. Coming back to the Extension Tubes, one could expect to get 1:2 in average (workable average see below). Here is an easy way to know what you can expect regarding magnification when using extension tubes:
Magnification change = tube_length/focal length.Therefore a 30mm Extension Tube (or a combination of Tubes) on a 50mm lens adds 30/50=0.6x magnification whereas a 30mm Extension Tube on a 100mm lens adds 30/100=0.3x. As your an see the smaller the focal length, the bigger the magnification providing the Extension Tube length remains the same.
Note 1While one could think that using a Wide Angle lens with an Extension Tube would offer some amazing performance (i.e. a 10mm lens with the three rings 21+13+31 would give a magnification of 65/10=6.5x) the issue one is bound to face with is the distance between the lens and the subject. Wide Angle lenses have a small minimal focussing distance, and you may end up being millimetres away from your subject which brings lighting difficulties.
Note 2You may found on Ebay many Extension Tubes for about £10. Be aware those are not the same as the £50 ones. The difference is a major one. Indeed, you may notice in the image of the Extension Tubes, the presence of rides inside the tubes. Those are meant for the camera to detect the lens and enable it to do tow things:
- Validating the focus (even using manual focus, it would beep when in focus.
- Passing on the Aperture information to the lens so it can change it. Without it, your lens will be stuck at its widest Aperture value which will have dramatic consequence see further below for more info.