Recently I've purchased the Kenko Extension Tubes set for my Canon 60D as I wanted to do a little macro photography without bringing out another lens, and adding on to my already heavy load. This post is to correct some misconceptions of what the extension tubes can do, something which I couldn't really find in the Internet.
First thing first, the extension tubes
do not increase the range of your lens. Translated, if you have a 17 - 55mm lens and you add a 12mm extension tube, your lens will not become a 29 - 67mm lens, and let you take pictures of objects/people further away.
So what do the extension tubes do? First, photos of the extension tubes.
The kenko extension tubes come in a set, the 12mm, 20mm, and 36mm. As you can see, there are no lenses but there are metal connectors so that the auto-focus will work, sometimes. I will explain it later.
The extension tubes will help reduce the minimum distance that you need to focus on an object, which in-turn makes the object bigger. Not only that, it also reduces the maximum distance that you have to focus on an object. Yes, what that means is that your maximum focusing distance will be reduced with the extension tubes.
I was quite surprised though that the maximum focusing distance was reduced. Something you may need to take note because if you're used to focusing at a certain distance, this distance will be reduced when you're using the extension tubes.
Oh yes, the extension tubes only work on your maximum focal length.
That means if your maximum range is 55mm, the extension tube will add on
to it. It doesn't work any other way.
Auto-focusing works fine until you use the 36mm extension tube where the auto-focus does not work that often. However, if you stack all the extension tubes, your auto-focus will never work, so manual mode is the way to go.
Do note that the extension tubes work best on long range lenses. For my 17-55mm EFS lens, only the 12mm extension tube works. Below is the picture I took using that lens at the minimum focus distance.
Now look at the picture below which I took with the 12mm extension tube fixed on, auto-focus.
I believe you saw some kind of shadow on the doll. The reason is because my lens was practically touching the doll. That's how close I could go with the 12mm extension tube.
Below is a normal picture I took with my 75 - 300mm lens at the minimum focus distance.
Below is the picture taken with the 12mm extension tube. Slightly closer.
And with the 20mm extension tube, the picture is even closer, as shown below.
Now with the 36mm extension tube, the picture is closer still, as shown below.
Finally with all the extension tubes stack up, and on manual focus, the picture is as shown below.
As you can see, the focus is not that great and this is one thing you need to take note when using the extension tubes. They will reduce the amount of light going in so unless you're using the 12mm extension tube, a tripod is a must because I feel it tends to exaggerate any camera shake.
Does this beat a dedicated macro lens? Of course not. But I rather save the space in my luggage for something else.