About macro extension tubes – P365 Nov03
This humble aluminium tube has opened up a whole new photographic world for me. The world of the small.
A series of tubes
All lenses have a limit to how close they can focus. A typical lens, for example, may not be able to focus on anything closer than 30cm. This is because as objects move closer to the lens, the focal point moves further back, eventually beyond the plane of the film or sensor. An obvious way around this problem is to move the lens further away from the camera. That’s what macro extension tubes do.
The macro extension tubes that I use are very cheap and simple. As you can see from the second photo above, it comes in five sections. At each end is a bayonet ring for mounting the tube to the lens and camera body (in this case Canon EOS). In between those any combination of three threaded tubes of varying length can be used to change the extension by varying degrees. That’s all there is to these tubes, nothing more.
Pros and cons
As with all compromises, there are trade-offs to the solution. This is especially true of a cheap, bare-bones solution like mine. Here’s the costs/benefits of tubes like mine:
- Moving the lens out from the camera sets an upper limit to how far away you can focus the lens.
- There is no auto function control over the lens, such as aperture or focus.
- The threads can be accidentally overtightened and thus become very difficult to seperate.
- The centre of gravity is moved forward and there is no tripod mounting collar, putting greater stress on the camera body’s lens mount.
- Moving the lens out and focusing closer makes the light rays more parallel at the focus point. This causes increased chromatic abberation which is much more obvious in high contrast macro photos.
- No aperture control means that in order to change it, the lens has to be set to the desired aperture while on the camera body, then with the camera on, removed from the body while holding the depth of field preview button to keep the iris at the desired aperture.
- Using the DOF preview hack to control the lens aperture, along with the fact that small scenes have less light on them, makes for an exceptionally dark view through the viewfinder.
- With no autofocus and a dark viewfinder, focusing manually can be extremely difficult.
- A natural and unavoidable effect of macro photography is an extremely small depth of field. This increases the need for a small aperture and the resulting dark viewfinder even more.
- Extreme close-up macro photos put the lens so close to the subject, lighting it can be very difficult. Side or back lighting may become your only options, as the lens gets in the way of the light.
- As there is no data connection between the camera and the lens, the camera has no idea what lens is attached, and as such much possibly useful information will not be stored in the images’ EXIF metadata. (Thanks to whipartist for this point, found via this discussion thread.)
- Photographic opportunities otherwise unavailable (without very expensive specialist lenses) are possible.
- Dirt cheap! (Mine cost $30AUD including shipping)
- Works with most lenses, except for those with very short focal lengths.
- A light and compact addition to your gear. I carry mine with me everywhere.
- Useful even with telephoto lenses. A long lens is great for making things bigger, but they can’t focus very close at all. An extension tube can allow you to enlarge with the telephoto but still maintain a good working distance.
- Mechanically simple. There’s not much that can go wrong with these.
- They’ll get you thinking about new ways to take photos. Extension tubes make your lenses a whole lot more flexible, and don’t just have to be for photos of insects or flowers.
There are, of course, ways around many of these problems. The most obvious one (and one to which I one day plan to graduate) is using official brand name extension tubes. They most likely have the needed connections to allow full control of the lens from the camera, and each tube is bayonetted, making swapping and stacking them far simpler. Of course this makes them more complicated and more expensive solutions. The ability to keep auto focus and apeture control is a huge advantage likely worth the cost, however. Here’s an example of one Canon extension tube. Note the cost for a single extension, compared to that of my five piece no-name tube.
If you have a bigger budget, or enjoy macro photography enough to justify the cost, you can buy specialised macro lenses. These are great for macro photography. They eliminate many of the problems, especially chromatic aberation, and can get you extremely close to the subject. Also, extension tubes can even be fitted to these, resulting in the possibility of some insanely huge macro magnification. They are specialised optics, however, and can be quite expensive, especially when compared to extension tubes.
Lighting for macro
This can be an extremely tricky and frustrating issue. In fact it’s worthy of a detailed post in itself, so I’ll only mention it briefly here. There are many possible solutions, including:
- Shooting in a light tent.
- Using reflectors.
- A professional ring flash.
- A macro flash bracket.
- Or even a super cheap and fast hack.
Final thoughts and links
Ever since I got these tubes, I’ve loved shooting macro photos. It’s a lot of fun and gives so many new opportunities. It’s a challenge to be sure, but that’s part of the fun. I plan to upgrade to “real” extension tubes in the future, but when the entry level gear is so cheap, there’s no reason at all not to try your own hand at macro photography.
Here’s some useful and inspirational links about macro photography:
- Macro group photo pool at Flickr.
- Equipment Options for Macro Photography at Epic Edits weblog.
- No Cropping Zone a blog about macro photography.
- How To: DIY $10 Macro Photo Studio at Strobist.
- Macro photogarphy at Wikipedia.