Teleconverter tests – Part 2
I thought I was done with lens testing for awhile, after that round of comparisons of four generations of 300mm Nikon optics. At least I thought the results were interesting. I think I can still hear you yawning.
If you recall (or scroll down to my earlier post) the results of the two different teleconverters I tested were interesting too. I had thought my ancient TC-200 converter was a perfectly good optic – until I put it up against the TC-301 that was supposed to be a better match for a 300mm lens. It’s no fun finding out that your earlier notions were all wrong.
Then just the other day, a third gizmo arrived on the scene, threatening the superiority of the TC-301. This is Nikon’s mighty TC-20E III, that not only boasts a hefty price, but also “aspherical” optics. How good would this be?
Well, if you can put something to the test, you must. And so out came the lens, test chart, and the two older converters.
But let’s have a short discussion about teleconverters first. Many of us recall when they were sold inexpensively as add-ons to our basic telephoto or zoom lenses. It was an easy up-sell to convince someone that the $229 aftermarket zoom lens they were buying (probably an 80-200mm, if this is 1980 or so) could be quickly transformed into a 160-400mm with an extra $50 gadget. Sold!
Trouble is, those converters got used once or twice, then got pushed to the back of the drawer after the results were, shall we say, a little disappointing? Stretching the limitations of a budget lens with a budget add-on wasn’t a recipe for sharpness. Often the exposure came out a little dark too.
I have what amounts to a scrap heap of these old converters from the manual focus era. Take your pick of lens mounts; I think I have them all.
So what happened to inexpensive add-on teleconverters? Where’d they all go?
I think a few things conspired to make the budget converter a thing of the past. The first was autofocus. Since AF cameras worked with lenses as slow as f5.6, f5.6 became the standard for the inexpensive (or not-so-inexpensive) zoom lens. Putting a 2x teleconverter on such a lens drops its effective aperture down to f11 – where autofocus often hunts and searches, if it tries at all. Converters intended for autofocus also have to have extra couplings and/or electronic contacts, which makes them more costly than their 1980-spec predecessors.
And then, of course, inexpensive zoom lenses got stretched to the 300mm range, at which point most people are quite happy and realize they can’t make good use of more magnification, especially with a crop-sensor DSLR.
But don’t professionals use teleconverters, I am often asked? Yes, yes they do. But putting a $400 or so converter onto a $3,000 or more lens isn’t quite the same thing. When a lens is big, heavy, and made with premium optics, then adding a little gadget to the bag that can boost its range by 40%, 70%, or 100% can be worthwhile, even if it costs you a little sharpness.
This is where these three Nikon converters come in. All were/are pro-grade for their respective eras.
The TC-200 (which was later made as a TC-201 with updated Ai-S couplings) is my old standard. As an old 2x manual converter, it means you have to put up with manual focusing on any newer AF lenses. G-type lenses without an aperture ring won’t work. But on the plus side, it was intended to work with and fit a wide variety of Nikon lenses, as its front element is nicely recessed. It has seven elements, which is a badge of a top-grade converter. Many companies, like Vivitar made both high-grade 7-element, and budget 4-element versions. Cheap converters were all 4-element, if you were lucky.
The TC-301 is an odd duck. No it’s not a 3x converter (Nikon never made one); it’s still 2x, but its name implied it was made for lenses 300mm and up. That big snout of a front element only fits lenses that will allow it inside. It has only five elements, but they’re obviously widely spaced out in a design optimized for big glass.
The newest one is the TC-20E III, and has one aspherical optic in its 7-element design. It’s noticeably heavy. The big thing, of course, is that it supports autofocus, and G-type lenses. The down side is the list of lenses it fits is quite small. A tab on the front mount physically blocks from fitting unapproved lenses, although some owners have resorted to modifying the mount to fit a few more.
One of the least costly lenses on the approved list is the 300mm f4.0 AF-S I happen to own, so that’s what I used for testing this time round. One lens allows us to learn something, even if we can’t learn everything.
So, the lens was mounted on my big tripod, converter and camera on the back. Focusing was done carefully on magnified live view, and the flash exposure was made with the mirror locked up. Hopefully this gets rid of any notions of camera shake ruining the data.
Again, the results were interesting. And again, the TC-301 came out on top. Unless there’s something wrong with the new aspherical converter, and I doubt there is, the old design showed it up – except perhaps with the lens used wide open (effective F8) where the TC-20E III is a tad sharper. But again, the TC-301 was best in the corners, and added less chromatic aberration to the image.
I didn’t bother testing how easy it would be to remove the chromatic aberrations in Lightroom or Photoshop, but rest assured, that might be helpful.
As you can hopefully see from the composited test shots, all three converters benefited mightily from stopping the lens down to an effective f11. Again, I didn’t bother stopping down further because I don’t think the world needs a 600mm f16 telephoto, sharp or not; f11 is dark enough.
So does this mean we can write off Nikon’s latest top-dog teleconverter as not living up to its obsolete predecessor? Probably not. Obviously the new unit allows AF with its approved list of lenses, but we have to concede that testing just one AF-S 300mm lens might not tell the whole story. This TC-20E III was built mainly to double the range of some really big, and really pricey optics. How well does it perform on a 400mm f2.8, or a 600mm f4, compared to the TC-301? I can’t say. And if and when the stars align enough to allow me to play with one of those behemoth optics, I probably won’t have the suitable converters around to run more tests.
At the end of the day, am I ready to retire my venerable TC-200, given that it came up dead last again? Well, no. Don’t forget it was actually designed for shorter lenses than the 300mm. However, while it fits, it isn’t recommended for my 80-200mm f2.8 either (I do recall some noticeable light falloff last time I tried it).
No doubt there’s a lens or two in my collection where the TC-200 will shine. I’ll just have to get out the test chart again to find out for sure. This time, I promise not to bore you with the results.