Testing a 25mm Extension Tube

A few weeks ago I tested a Macro Effect filter. The results were not that impressive. I decided to spend some more money on an original Canon EF-25 II Extension Tube (the “II” is critical if you have EF-S lenses).

The Extension Tube is simply a 25 mm long piece of metal pipe, that fits perfectly between your camera and your lens. You can get cheap ones (that doesn’t have electrical connectors) or expensive ones. They have no glass anyway.

Moving the lens away from the camera (sensor) has two effects:

  1. it crops the picture, making objects larger
  2. it changes the shortest possible distance usable for the lens

It is the second effect is the crazy cool one. For my two EF-S lenses, and my fixed 50mm EF lens, this is the effect:

   Lens        Original Range               New Range (roughly)
   18-55 mm     25 cm - infinity             0 cm - 20 cm
   55-250 mm   110 cm - infinity            15 cm - 400 cm
   50 mm        45 cm - infinity            10 cm - 15 cm

So, I can get really close to the object. However, it is now impossible to focus on anything far away. There is of course some math, some science, and some theory about this, but I dont really know much about it.

With the extension tube on, zooming does not really work as expected. Instead, the zoom decides the rough focus distance. So, for the tele lens, at 55 mm I can focus on things roughly 15 cm away. As I zoom in towards 250 mm, the focus distance increases to 4 meters. The size of the object in the lens is somewhat constant, since I move away from the target at the same time as I zoom in more and more. The focus ring can be used to fine-adjust focus, but if the zoom is not fairly correct, you can never get focus. With some luck, auto focus works.

Train revisited
Of course I started photographing the same train as I did with the Macro Effect filter. RAW mode used, picture exported to JPEG with iPhoto.

18-55@44, 2.5 sec (ISO800), ~15 cm from object

As I see it, the picture is much better than what was achieved with the cheap Macro Effect lens. Especially, the picture is sharp not just in the middle. Lets look at a crop:

Crop of text details

As I see it, this crop of the center of the picture is slightly sharper than with the Macro Effect filter.

Finally, something more artistic.

18-55@36, f/9.0, 1.6s, ISO100

Even if this is at 36 mm, I cant get much closer, because the object hits the lens. Not possible to go all the way down to 18 mm.

18-55@53, f/9.0, 5s, ISO100

Would I recommend anyone to pay almost EUR 150 for this thing? Well, it is small, and it turns your 18-55 kit lens into a macro lens. The result is much better than a cheap filter. Perhaps for the 18-55 lens it is better to get the 12 mm extension tube…

For more nice macro photos, try this page.

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