The Tamron 90mm SP, regarded as a hot macro lens about 20 years ago in its Adaptall-2 form, could be used with a Tamron x2 teleconverter specifically for the extra magnification. All the Tamron tele-zooms of the time had magnification scales too, one of the features of the range. When you think about it, the difference between magnifying the image and increasing the focal length is practically non-existent. Put a wide-angle shot into your computer (easier than doing it in an enlarger), crop and scale to match the same view through a long lens, and the only obvious difference is the image resolution -- pixels or grain, do the magnification with the camera if you can. But I hadn't much thought about the extension-tube effect. I have a set, but if I wanted big macro images, I still have a Tamron 80-200mm and teleconverter. But that particular Tamron converter has to go between the lens and the Adaptall mount. The teleconverter quality will certainly make a difference, and they give you that longer lens too, without adding a lot of weight to your kit.