Pixco-ext-tubes

Those of you that know me, know that I’m a big fan of doing things as cheaply as possible, (whilst still retaining quality obviously :-) ).

In this vein, I recently bought myself a set of Auto Focus extension tubes for my Olympus e-PL1 CSC camera.

The camera’s kit lens is a 14-42mm zoom and with the 2x crop factor, that gives you a 35mm equivalent of 28-85mm.

This suprisingly sharp (for a kit) lens has a close focus distance of 25cms and although the camera has an adequate pre-set macro mode, I was looking for more magnification without the expense of a dedicated macro lens.

I looked at various manufacturers from Kenko, who are at the top end of the quality tree (at a price around £100), to some very obscure ones that, while they probably work a well as the more expensive types, are more likely to fail in one way, or another.

So, I decided on a set of two tubes from Pixco. These tubes are available from Amazon, or ebay, etc for about £20 a set

The set contains a 10mm and a 16mm tube, which with the lens at a focal length of 26mm, gives a 1:1 image on the sensor.

For those of you that aren’t sure how an extension tube works, it’s an attachment that goes between your camera body and your lens. Unlike close-up lenses (which are also known as diopters), it has no optical element, so there’s no reduction in image quality. All it does, is get the lens further away from the focal plane (the surface of the image sensor). Now, by moving the lens further from the sensor, your minimum focusing distance gets smaller, therefore the subject is closer to the front optic of the lens. As a result, you can get closer to your subject; you can fill the frame with more of it, and still achieve focus.

The benefit of choosing a set of extension tubes with the electrical contacts, is that you can set the camera to Aperture Priority, select your f-stop to give you sufficient depth of field and retain all of the camera’s metering systems, auto-focus, etc. You can buy much cheaper extension tubes that don’t have these contacts, but you’ll need to use the camera in full manual mode.

The images below show the same subject, the first with the camera set to it’s minimum focus distance (25cm), the second image has the camera set to it’s ‘macro’ mode (10cm) and the last image is the lens when attached to the extension tubes (1.2cm).

Olympus e-PL1 with 14-42mm lens at Min focus Distance

Olympus e-PL1 with 14-42mm lens at Min focus Distance

Olympus e-PL1 with 14-42mm lens set to Macro

Olympus e-PL1 with 14-42mm lens set to Macro

Olympus e-PL1 with 14-42mm lens and 26mm extension tubes fitted

Olympus e-PL1 with 14-42mm lens and 26mm extension tubes fitted

 

Obviously, there is a limit to the number of extension tubes you can fit to your lens. With 26mm of extension tubes fitted to this camera and the focal length on the lens set to 20mm, the subject focus point was inside the lens, so I had to zoom-out to 34mm until I could achieve sharp focus and get enough light between the Lily and the front optic of the lens.

For this shot, I was at f7.1, ISO 100 with a shutter speed of 6 seconds.

As you can see from the image above, it’s not necessary to have a macro lens to get macro images. All of the images above were taken straight from camera, with the only adjustment being to reduce the image size.

So, I guess the next question is “Why should we bother paying £500 for a macro lens, if we can get the same results from a £20 set of extension tubes?”

Well, as with everything, when you pay less, you generally get less!

Some of the more important things to consider are;

 

  • The biggest difference you’ll find when using a dedicated macro lens, is the close focus distance will usually be somewhere between 5 and 10 inches from the subject. This gives you so many more opportunities and allows you to be more creative because the subject doesn’t have to be almost touching the lens.
  • A manufactured macro lens has been designed to give a ‘flat’ image at close distances. This means basically that the optics have been designed to stay extremely sharp at close focus, even at the edges. Because a zoom lens is designed to have a degree of sharpness throughout it’s focal range, sometimes the edges of the image can be soft when it’s used for close up photography. Especially if the subject fills the entire frame. This is especially a problem with some ‘kit’ zoom lenses that, in many cases are manufactured on the lower end of optical quality.
  • Also, for each extension tube you add, you lose at least one stop of light to the sensor. In my example above, to get an image that was sufficiently sharp, I needed to increase my depth of field in lighting conditions that weren’t perfect, which cut down the light even more. I ended up needing a shutter speed of 6 seconds to get the same exposure as the first image which had a 1/4 second exposure.
  • Next, because the lens has been moved further from the sensor plane, your auto focus will struggle to lock on and, although it’s often the same with some macro lenses, you should always put your lens on manual focus when using extension tubes. You can then move the camera backwards and forwards to achieve sharp focus.
  • Additionally, a tripod is a must when using extension tubes. As you can see from my final image above, even the edges of the Lily’s stamen is beginning to become soft. The depth of field,even at this aperture (f7.1) is barely more than a millimetre, so hand holding your camera is not recommended.

If, after trying macro and close-up photography you decide that this is the niche for you, then a macro lens would definitely be worth the expense, but a set of inexpensive extension tubes will certainly do the job.