This is the second in a series of four lessons on close-up and macro photography by Andrew S Gibson, author of Up Close: A Guide to Macro & Close Up Photography.
In the last lesson, I wrote about close-up lenses and how they can help you get closer to the subject for close-up photography. This time, I’m going to write about another accessory you can buy, extension tubes.
Extension is the term used to describe the distance that the front element of your lens can be moved forwards. The further forward the element, the closer your lens can focus to your subject.
Extension tubes work by increasing the extension of your lenses. An extension tube is a hollow, light-tight tube that fits between your lens and your camera mount. It moves your lens further from the camera, and the front element closer to the subject. The closer you can focus, the more magnification you get.
The above photo shows a 50mm lens fitted with a 25mm extension tube.
Extension tubes, generally speaking (it depends on the lens) get you closer to your subject than close-up lenses, in some closes nearly as close as you would be able to get with a macro lens.
There are two types of extension tube that you can buy:
The first, and the least expensive, don’t maintain the electrical connection between your lens and camera body.
The camera can still handle exposure – just set it to aperture priority or program mode.
The biggest drawback of these extension tubes is aperture control. If your lenses don’t have manual aperture rings (ie the aperture setting is controlled by the camera) then the lens aperture will remain locked open at the widest aperture. While wide apertures can be used creatively, the narrow depth-of-field you get with close-up photography means that you usually need to stop down to get a large enough zone of sharpness to suit the image.
However, if you have a lens with a manual aperture ring, this may not matter too much, as you can stop down manually (although the viewfinder will get darker as you do so, making it hard to see at small apertures).
The second type of extension tube is one with electrical contacts that maintains communication between the lens and camera body. The camera controls the aperture settings, and you can use any automatic exposure mode and also autofocus (although it is often easier to focus manually when you’re working close-up).
These are the Canon EF25 and EF12 extension tubes (now discontinued and replaced with the EF25 II and EF12 II tubes). You can see the electrical contacts in the extension tubes.
You will find plenty of inexpensive extension tubes if you search on Amazon or eBay, and they are fine if you are on a tight budget or just want to play. But if you can, you should buy the second type of extension tube, which is one that maintains the electrical connection between the lens and the camera body.
Nikon, Canon and Olympus make extension tubes for their cameras. Sony doesn’t, but you can buy them from third party manufacturers like Kenko and Vivitar, who also make extension tubes for Canon and Nikon. These tubes are all of the second variety.
Pentax is the odd man out here – the only extension tubes I could find for sale online were more expensive than a Pentax macro lens (I don’t know why). But if you’re a Pentax user, you can buy the first type of extension tube I mentioned easily enough, as long as you’re willing to work within the limitation of losing the lens to camera electrical connection.
Extension tubes work best with lenses of short to medium focal lengths. They are less effective with telephoto lenses.
This is the opposite way around to close-up lenses (see my first article here), which work better with telephoto lenses. The focal length of the lens you intend to use for your close-up work may determine which is the best accessory to buy.
An advantage of extension tubes is that you can use them with any of your lenses. If you buy a set, you can join two extension tubes together to give you even more magnification.
The only disadvantage of extension tubes is that there is some light loss. Adding an extension tube increases the effective aperture of the camera lens, which means you need to use either a longer shutter speed or higher ISO to compensate for the loss of light. Your camera, if it’s set to an automatic exposure mode, will take care of this automatically for you.
Using extension tubes
The best way to use extension tubes is to set the lens to manual focus. You can use the manual focusing ring on your lens to focus on the subject.
Depth-of-field is very narrow this close up. Don’t be afraid to raise your ISO in order to get a small enough aperture to give you adequate depth-of-field. If your subject is still, you can use a tripod – this will let you use a low ISO to maximise image quality and eliminate camera shake.
If you are hand-holding the camera, you may need to use a faster shutter speed than normal to obtain a sharp image. The extra magnification also magnifies camera shake as well as the subject. Shutter speeds of 1/250 second or more are ideal.
What sort of thing can you take photos of with extension tubes? I like to use them for taking photos of flowers. I also had a lot of fun taking photos of my girlfriend’s eye (the opening image to the article). It’s a good illustration of how close you can get if you stack enough extension tubes together.
You can learn more about close-up and macro photography in my new ebook Up Close: A Guide to Macro & Close Up Photography, available now from Craft & Vision.