What are extension rings?
Above is a full set of Soligor extension tubes. You might be wondering what extension tubes are and what you can do with them and I wish to show you some interesting stuff. First of all, this article is for the beginners, if you already know what to do with them you can just skip on.
If you are new to advanced macro photography this is a really good help for you. If you already own a macro lens (I use the Tamron SP Di 90mm f/2.8 Macro 1:1 lens which is a very good lens in many ways but to achieve really close pictures you need more magnification than 1:1.
This is what extension tubes do. They move the lens away from the camera, meaning that the image the lens produces falls outside the sensor. Think of it as if your digital camera just suddenly saw a tiny part of the picture the lens produce and then made the picture from this part. Exactly this is the purpose of these extenders.
The extension tubes can be used separately for lower magnifications and together to provide a wide variety of magnification ranges depending on what you are shooting. Here are all the possible combinations in increasing length:
- 12 mm
- 20 mm
- 32 mm (12+20)
- 36 mm
- 48 mm (12+36)
- 56 mm (20+36)
- 68 mm (12+20+36)
There are variants of course, many other brands to chose from. I chose Soligor because they were easily available, the cost was low and – in my opinion this is important, they allow the camera to meter and autofocuse when they are mounted, the cheapest onese usually don’t do that.
Now, with advanced macro phootage you may not be able to focus with AF anyway, the depth of field is so shallow that it is easy for the focussing mechanism in the camera to actually step over it and miss the sweet spot. With a bit of practicing that’s not a problem you will learn to focus manually.
These rings – or tubes – also have the electrical connectors that allows the camera to transfer information to and from the lens. This is important for the metering feature to work properly. If your rings do not do this you will have to go fully manual on your camera to use them.
What is the good things about them?
They allow you to get close. I mean really close to your subject. They also allow you to do crazy shallow focus depth (DOF, depth of field) meaning that the space where your subject is in focus is very very small. This is very interesting for some types of shots. Some examples here:
These were all taken using my trusty Tamron SP Di 90mm f/2.8 Macron 1:1 lens which I love dearly. But extenders can be used with other lenses as well. I have tested it with my Nikkor AF 50/1.8D lens and this works well.
So if you do not have a macro lens, a cheap way of getting macro shots anyway is to use a good lens you already have and then add extension tubes. This works not so good with wide angles or too long telephoto lenses, you should probably be somewhere around 30-100 mm in focal range for this to work well.
Together with a macro though it allows you some crazy control over the pictures. Macro lenses also often have the possibility to step down to something like f/48 or f/64 which means you have good control over the depth of field and can definitely play around with it.
Drawbacks of using the tubes?
There are some drawbacks of course. When they are mounted the camera can no longer focus at infinity. You can not use these to enhance your telephoto lens for this purpose you need a different breed called a teleconverter which is not just a tube but also has a lens to correct for the focal length change.
Autofocus may become difficult since the extension makes the depth of field very shallow it may be difficult. The light through the lens is also diminished somewhat but the camera compensates for this but some cameras needs very good light for their focus sensors to work. Mine works pretty well down to about f/8 but not beyond that generally.
Because of the light conditions, the very shallow dof you will most likely need a very good light source as well. I use my SB-600 flash, but on a tether (cable) so that I can move it around and work with it from different angles. I recommend something like that or a ring flash or similar because you need good light to be able to work f/40 to get something that looks like a decent DOF when useing the extension tubes.
But then light is always a problem of macro photography, not only of extension tubes.
What should you consider when buying extension tubes?
Check that they have the electrical and mechanical couplings necessary to transfer information to your body for metering and autofocus to work. If these two things does not feel that important to you, if you are happy to shoot on manual and focus manually then by all means you can get the cheaper tubes of course. I personally prefer to have the option of using the AF and 3D metering that my camera offers, even if I wish to turn it off.
Get a known brand of them and google what people say about it being used on the lens mount and camera type you are using — i have heard people who use really cheap bad ones had trouble getting their lens to fit or the rings to fit the camera house, the precision may not bee very good on these.
The rings are different for different camera brands, make sure you get the right ones for your camera brand and lens mount.
What is the price?
Around €110 (£70 GBP, $165 USD) for a full set or varying where you buy them. I got mine online in sweden at Cyberphoto. You may also pick up used ones on Ebay or similar trading places. The ones without the electrical connectors are cheaper and then there are some very cheap ones I would not recommend because of the poor quality. You don’t want to damage your camera lens mount or your expensive lenses.