I recently was looking at extending the reach of my lens sets at the long end for both Nikon 1 and Micro 4/3, but doing so without a major outlay of bucks. I decided to experiment with front-mounted teleconverters, after reading some very interesting blog postings from a fellow named Dr. Ching-Kuang Shene who had done similar experiments with some older Panasonic super-zoom cameras. http://www.cs.mtu.edu/~shene/DigiCam/ I've been doing some significant experimentation with several high quality front-mounted TCs that can presently be picked up at dirt cheap prices on ebay, because their target cameras and lenses are long obsolete. In the course of this exercise, I picked up several of these converters that had a reputation of being good. Well, it's really a function of matching the converter to a lens that is the right physical size and focal length. The converters I picked up for this test are: Titanium Digital 2X front converter: This cost me $7. 46mm threads: Short answer, this is junk - loads of purple fringing and loss of sharpness on every lens I tried it on - skip it. Olympus IS/L A-200 1.5X front converter: This cost me $12. 49mm threads: Short answer - it's VERY good for lenses that it is the proper size for. It matches up extremely well with my Micro 4/3 45-175mm zoom, with ZERO observed added vignetting or distortion at the long end, and no apparent light loss. Sharpness is well maintained and color fringing is quite minimal. This converter also matches up well with the Nikon 1 30-110mm lens, but I found one that's even better for that. It's a bit heavy for a 1.5X converter for the Nikon 1 30-110mm lens - a bit over 6 ounces, but the quality is first rate. Olympus IS/L C-210 1.9x front converter - This cost me $25: 52mm threads: This is your winner for the 30-110mm lens. Interestingly, this converter is physically quite small, with a small rear element, so it tends to vignette and lose light with most lenses I tried it on, but the 30-110mm Nikon 1 lens is so small, that this converter's shortcomings with larger lenses, don't appear with the 30-110. Sharpness is excellent, AF speed is excellent with that lens, the VR still works, and it doesn't vignette on the longer half of the 30-110mm lens' zoom range - first darkening the corners when that lens is zoomed out to between 55 and 60mm. Because the front element is much larger than the front element of the 30-110mm, there is also little or no light loss. In other words, the 30-110 f5.6 becomes a 209mm f5.6 at the long end with this converter. Also - this converter weighs less than 5 ounces, so it won't stress the AF mechanism of the 30-110mm, or the Nikon 1 lens mount. Olympus C-210 front mount teleconverter is an EXCELLENT match to the 20-110mm lens. This TC is a 1.9x Front-mounted TC that was developed for a long-ago fixed lens Olympus camera series known as the IS/L. There is also a 1.7x version called the C-190 Basically, those numerical designations indicate that they convert their designated target lenses into 210mm and 190mm respectively. Which, it happens, is just about an exact match for what these TCs do when mounted onto the Nikon-1 30-110mm lens. Olympus TCON-17 (this converter is also identical to the Olympus IS/L B-300). This is a 1.7x converter that screws onto 55mm threads. This cost me $50. This is a well regarded front TC, but it's too big for the Nikon 1 30-110mm lens. It weighs 10 ounces. But I would bet that it does very well on the 70-300 cx lens. It performs quite well on my Tamron 70-300 lens, with no vignetting in the DX frame, let alone the CX frame. There is some light loss, however - about 1 f-stop, and as a result, AF performance becomes a bit sluggish. But optical performance is quite good. Sony HG1758 High Grade 1.7x converter. This screws onto 58mm threads. This cost me $15. This is a big, heavy unit. it weighs just over 15 ounces, and has a front element that's 90mm wide. As a result, it works very well on my Tamron 70-300mm lens with no vignetting and no observed light loss. Optical performance is at least as good across the DX frame as the TCON-17, but this converter is simply too bulky and heavy to use on any native Nikon 1 lenses, or Micro 4/3 lenses, for that matter. I still haven't decided between the TCON-17 and the Sony HG1768 which one is a better match for my Tamron 70-300. The Sony appears to be slightly better optically - with no compromise with regard to vignetting or light loss, and very good sharpness across the frame - but that is at the expense of significant added bulk and weight. In any case, for Nikon 1 users, it's clear to me that the best choice for use with the 30-110mm lens is the Olympus C-210, and the Olympus A-200 and C-190 are also good alternatives. if I had the 70-300 native Nikon 1 CX lens, the Olympus TCON-17 and it's identical twin the B-300 are probably very good choices - although I've not tried the combination. For larger Nikon DSLR glass being adapted, I believe that both the TCON-17/B-300 and the Sony HG1758 are viable options, but the Sony is just too massive for use on any Nikon 1 native lenses. For Micro 4/3 users, any of the 40-150, 45-150, 45-175 mate well with the Olympus A-200 with no optical compromises at all, and a 1.5x magnification. The 1.7x or greater converters all either have a size/weight compromise, or a vignetting/light loss compromise, but may still be useable options. For use with the 100-300mm lens, I am betting that the TCON-17/B-300 are the best choices, although I have not tried the combination.