The obvious explanation of Macro Converters, and extension tubes in general, work is actually fairly simple and one of those things that are obvious once you know.

So, to start with conventional tubes, if you look at almost any manual focus lens, or a Lensbaby (some AF, zoom, and very long lenses have internal focussing which is not visible from the outside) and watch what happens as you turn the focus ring you will realize that as you focus closer the lens glass or Optic, moves further away from the sensor.

In the 50mm lens above, the extension between close focus and infinity should be obvious. This leads to the question, what happens if I move the lens further away from the camera? In this case, an extension of 29mm gives a close focus distance of about 7cm and a magnification of about 1:1.4 (magnification is defined as the ratio of subject size to the size of the image on the sensor, so 1:1 Implies that a 1cm high object would project a 1cm high image on the sensor, 1:2 a 0.5cm image and 2:1 a 2cm high image. Generally, any image with a 1:1 magnification or greater is regarded as a macro). The downside of this is that the same extension reduces the furthest focus distance from infinity to about 9cm!

Conventional extension tubes work fine with Lensbaby lenses, but the Macro Converters are smaller and lighter. The results are very similar for much of close-up photography, whether used straight or tilted. However, the Macro Converters maintain the Sweet Spot placement using extension tubes.

So, to summarise,

Magnification with any extension tube is greater with shorter focal length lenses. If you want to use longer lenses, such as the Edge 80, then Macro Filters or Close-up lenses have more effect.

Macro Converters and extension tubes do the same thing (move your Optic further from your sensor). Macro Converters preserve your sweet spot placement with any given amount of tilt by moving the Optic but not the ball and socket mechanism of the Composer forward while extension tubes move everything forward, making it possible to tilt your sweet spot off the long end of an image even when using a full-frame sensor. The images above had the same amount of tilt, but the statue was placed differently in the image using the Macro Converters.
Both Macro Converters and extension tubes magnify your sweet spot, so the Sweet effect decreases at any given aperture. If you want to preserve the (smaller) sweet spot size that you're used to, then use Macro Filters or Close-up lenses.

One final interesting fact, with the 12mm Fisheye Optic and the 8mm macro converter, you can focus on a bug/flower/whatever right on the front element of your Optic. With the f/32 aperture, it makes a great environmental portrait lens, the only problem being getting enough light past the lens!

One thing that should be remembered is that as magnification increases, the depth of field DoF) decreases. It is not unusual for macro photographers to take a series of images, each focused slightly further away from the camera, and then combine them to get a complete image in focus.

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