Strange hardware

Ever since I picked up an EagleEye^? 8x teleconverter from CrystalVue^? for my Coolpix 995 and managed to get some of my best pictures with it, I've had a liking for lesser-known hardware to help get to extremes. In particular, when most of the SLR world leans towards the 1.4x and 2.0x teleconverters that go behind the lens, I'm willing to put glass in front of the lens to extend my reach, which potentially allows a better aperture for the extension since the end glass can be bigger. My 8x converter definitely didn't cost me 4 f-stops.

These things are somewhat harder to track down than regular converters, typically I can find them on Ebay and go from there. So here I'll collect pointers (at first) and experience with such beasts. Asking about them on forums have given mostly two groups of answers, either "yeah, I'd like to know too", or "why would you want to do this, anyway". Very little actual experience, let alone rigorous tests.

Teleconverters

Having used a 1200mm equivalent with success (if some work), my first goal is to get out to that length again. Of course, my current lens doesn't help, going only to 200mm equivalent, so actual tests will have to wait until I have the Canon 70-300mm f/4-5.6 IS USM I'm lusting for (which has 58mm outer thread.

F-stop loss estimates are made by taking 2*log_2(tele/(front thread/back thread)^2). This is the lowest number of f-stops this converter can theoretically cost. Most likely, it costs more.

[[http://www.ckcpower.com/crystalvue.htm][EagleEye 8x teleconverter

Front thread 35mm (?), rear thread 28mm, 8x tele.

Focus Optics 2.5x tele converter

Front thread 72mm, back thread 58mm, 2.5x tele, gives an f-stop loss of as low as 1.4. 278g, 52mm long.

Some sharp warnings against Focus Optics.

Kenko KUT-HI 3X

Optics 2x

58mm rear thread (and others up to 72mm -- which means they could be stacked outside some of these other ones!)

Digital Concepts 2.5x

72mm front thread, 62mm rear thread. Also in 72mm rear thread.

CrystalVue^? 3x

52mm rear thread.

Mercury 3x

52mm rear thread.

Century Optics 2x

Tiffen 2x

Only small thread sizes?

Kenko 2x

52mm at most?

Raynox DCR-2020 2.2x

Front thread 82mm, rear thread 62 mm, yielding an f-stop loss of only .66. Impressive for >2x, but seems to suffer from vignetting.

Interesting sites

Kazutoku's teleconverter site

New World Video - has a collection of teleconverters, and rate between 7 and 8 on resellerratings, so not a scam.

Lensmate Online - adapters for compact cameras, up to 58mm outer thread. This makes them interesting for compatibility with the 70-300.

-- LarsClausen - 18 Dec 2006
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