Cheap Macro Photography – Extension Tubes

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 1

While 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 2

You 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.

Is there any drawback with Extension Tubes?

As just mentioned above, the singular way the Extension Tubes work is in getting your lens closer to the subject so if you want to capture some insects, they might not let you get up close and personal and may run away. That is a valid point for any Macro lens that is not a zoom. The closer you get to the subject the less light it receives directly as the lens may obstruct the beams, so you need to bring light by using a (ring) flash or reflector. The longer your Extension Tubes, the less light travels through the lens all the way to the sensor, so you need to increase the Exposure time. However, this is a consequence shared with Macro lenses as well: As we have seen in the episode The Creative Aperture: DOF, the Aperture value defines the DOF. However, there is a second factor to bear in mind: The distance to the subject. As a matter of a fact, the closer you are from your subject, the shallower the DOF. By definition, Macro photography you are bound to be pretty close to your subject (even with a zoom Macro lens). Therefore your DOF is bound to be shallow, and maybe even too shallow to do anything productive. To compensate, one needs to increase the Aperture value hence real Macro lenses let you achieve f45 and beyond. Using such Aperture value will extend the Exposure time. So whether you loose light by using Extension Tubes or using a very narrow Aperture, Macro Photography implies long exposures which imply a steady Tripod. As we have just seen, Macro lenses are built to compensate for a shallow DOF. When using Extension Tubes, you are obviously using lenses that are not designed for Macro and it is most likely that the narrowest Aperture you can achieve is f22. So not only the Extension Tubes let you get closer (even more than a Macro lens), but you have no mean to compensate for the shallow DOF. Of course, adding some distance between the lens and the subject will result in a smaller magnification.

Conclusion

Extension Tubes are not equal to a real Macro lens, how could they. They are nonetheless, a lot cheaper and can be the best introduction to this amazing world that is Macro Photography.