Again, thanks everyone! You do keep displaying this group's readiness to help the ill-informed, AND some themes ring pretty consistently throughout the input. alfeng's reply was loaded with tips from the basic "use a tripod" to "look for a used 7-element TC, then resell if you decide to pony-up for a prime telephoto." Another succinct tip was stated well in amfoto1's last sentence quoted below.
amfoto1 wrote:
The Kenko 1.4X "MC-4" teleconverter is quite sharp in the center, but a bit soft toward the corners. That's no problem on most crop sensor cameras, which only use the center of the image anyway. But for use on full frame, the slightly more expensive Kenko 1.4X "Pro-300" has better edge-to-edge, and corner sharpness, though it's not quite as sharp as the MC-4 in the center. I don't know how the 2X Kenko TCs compare.
HOWEVER NONE OF THIS MATTERS because the original poster is using a Canon EF-S 18-200mm lens which cannot even be mounted onto either of those teleconverters. That lens is also not usable on any of the Canon, Sigma or Tamron teleconverters.... probably not a Promaster, either. With only one exception I know of, teleconverters can only be used with Canon EF lenses... not with EF-S, which use a modified mount.
Kenko now makes "HD" teleconverters in both 1.4X and 2X strength... and their Canon versions CAN mount an EF-S lens. The Kenko "HD" are a little more expensive than their MC-4/MC-7 and Pro 300... but a lot less expensive than the Canon teleconverters (which are excellent, but wouldn't fit anyway).
HOWEVER... the EF-S 18-200mm is ALSO an f/5.6 lens.... so the original poster will lose autofocus with either 1.4X or, especially with 2X. The 18-200mm with a 1.4X would "become" a 25-280mm f/8 combo... or with a 2X it would "become" a 36-400mm f/11. The Canon 60D's AF is "f/5.6 limited", meaning it would not be able to autofocus either of those lens/teleconverter combos. Further, the viewfinder will be dimmed down, especially with the 2X and f/11 combo, making it near impossible to focus manually. (Might be able to use Live View with Exposure Simulation, though it will be slow.)
AND... image quality would also almost certainly suffer noticeably. 18-200mm are not a good type of lens to use with a teleconverter. Broadly speaking, most zooms simply don't work well with teleconverters... Especially wider ranging 10X and greater zooms like the 18-200mm. Prime lenses with less complex optical formulas work better with them. A few zooms are optimized to work with well them too (Canon's 70-200s and 100-400s, for example... there's even a Canon 200-400mm with a built in 1.4X... notice that the range of these zooms aere 3X, 4X and 2X, respectively).
When you want more than 250mm, there just aren't many "cheap" options.
The Kenko 1.4X "MC-4" teleconverter is q... (
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Other repeated themes, I think:
> The 1.4x version TC is likely to be more satisfactory, photo quality-wise, than a 2x.
> If I decide to try a TC, the Canon may be the best product, but it will require some other lens than I have in my bag now. robertjerl provided a helpful lens compatibility list that I should have been able to find, but had not.
> With the right lens, Tamron TC can work, according to DWU2's and cmaxi's experience.
> Several happily use Kenko TCs with Canon camera and various appropriate lenses, including TomV, jerryC41, DannyK, and agillot. amfoto1 mentioned Kenko as the one brand that has a TC model that works for EF-S lenses.
> Prime lenses are a much better choice to use with a TC! Or just save up for quality big zoom....an L?
> Shop the used market for good condition TC...or quality zooms or primes. The TCs are durable, and good ones are resellable, should you decide on a different direction. Many happy buyers of used gear here, I think, including myself: Notorious T.O.D., alfeng, amfoto1, JimRPhoto, scooter1. Some, like JimRPhoto prefer to buy used locally in order to inspect personally. I've done that as well as trusted ratings from KEH, BH, and Adorama.
> TomV suggests that TC+lens matched sets work great.
I hope I'm not skipping too many contributors; all comments have been enlightening and appreciated. I"m sure I haven't summarized all useful points. Perhaps the one most concise comment, though, might be amfoto1's To exceed "250mm there aren't many cheap options." - relevant to my specific inquiry.