Another item which I ordered from Deal Extreme is a Canon macro extension tube. This one is truely cheap and you don't have to consider before buying one. The closest alternative should be the one from Kenko and the Kenko is a step up from this one for sure, since the Kenko will allow you to change aperture, and it also retains the auto-focus ability of the lens. Of course, it comes with a price. Guess what, the Kenko is 10 times more expensive! That's why I buy this one without any thought.
To adjust the aperture, you can put the lens on your DSLR without the extension tube. Set the aperture of your lens (say in Aperture Priority mode), then press-and-hold the deep of field preview button on the camera, and then remove your lens at the same time. Done.
To adjust the focus, remember to switch your lens to manual focus mode, and you can do it by hand. People always said for macro photography, manual focus is always desirable. Simple, right.
For macro photography, we are interested to know the magnification of your setup. I've found a method to find out the magnification here. To skip all the detail, here we goes:
1. Find out the original magnification of your lens here.
Suppose we are using a 50mm f1.8 II lens, the maximum magnification is 0.15
With this value, we can calculate the effective built-in extension (X) by solving this equation:
X / 50 = 0.15
So, we have the value of X = 7.5mm
And now the new magnification is the length of your extension tube.suppose it's 25mm so the new effective extension will be X + 25 = 32.5mm
So, put the value back into the magnification equation:
Maximum Magnification = 32.5 / 50 = 0.65
Simple? Yes!
Here are some of my first shots:
An illuminating switch:-
Guess what?
That's it, the same lens without the extension tube:-
All hand held, and very rough focusing.
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