Teleconverter

Well, I think the BEST teleconverters are usually the highest-priced, manufacturer's own brand of 1.4x models, used with PRIME lenses.

Some of the VERY-newest TC units, like Nikon's brand-new aspherical-element designed 1.4x, the so-called "third generation" autofocus TC 14e-III converter, are very advanced, and with the newest, best Nikon lenses, provide pretty good image quality.

Canon's VERY-latest 70-200 f/2.8 L-IS USM Mark II is a professional-grade zoom lens that was, I am pretty sure, designed to compete with Nikon's pro zoom and Nikon's new aspherical converter breakthrough; the NEW, Mark II 70-200 works very,very well with Canon's 1.4x TC unit.

In carefully controlled tests, the newest, best, most-expensive manufacturer's 1.4x converters provide performance that was impossible to get just a few years ago. Part of this is that the converters have been optimized for certain design parameters, and I think also, the lenses have been designed with specific, manufacturer-designed converter use as a distinct possibility.

What **is** a waste of money is plopping a bad converter, or even an average-performing converter, onto a lens which it does not work well with!!! A slow, average zoom lens + an average converter is going to produce sub-par results; I think now that we have better, higher-MP sensors, that the 1.4x converter of average quality, on an average lens, is a total WASTE OF TIME; you would be better off just shooting with the lens itself, and cropping-in at the computer.

Also, keep in mind, converters usually produce a decent quality at the center of the image, but noticeably poorer edges, and corners. On "some subjects", like portraits, or birds, or wildlife, where the main subject is placed mostly in the center of the frame, the poorer image quality at the edges is often "no big deal". On landscapes or nature photos however, the poorer edge and corner performance might be VERY unacceptable. Usually, stopping the lens down two stops will make the loss of image quality at the edges less-apparent--but two stops down from wide-open, plus the one f/stop of light lost to a 1.4x converter, or two stops' worth of light lost due to a 2.0x converter, might affect shooting decisions in the field.

I generally think that a 1.4x converter is normally at least "acceptable" on high-end lenses with fast maximum apertures. On consumer zooms and prosumer zooms, like f/4~5.6 or f/4.5~5.6 zooms like 55-300 or 70-300 or whatever--NO, a converter is a waste of time and image quality. Similarly, I am not a big fan of 2x converters; the loss of effective f/stop is a deal-breaker much of the time, and the I.Q. loss from most 2x TC units can be EASILY, clearly noticeable on "most" lenses.

The bottom line really though is this: you need to carefully TEST OUT EACH CONVERTER/LENS PAIR, to see how it works FOR YOU!!!!! On your subjects, in your area. For example, in July-September in BRIGHT sunlight, you may be able to drop the lens down to f/5.6 and lose one f/stop and STILL have plenty of light at an effective f/stop of f/8, to still be able to get high speeds and sharp shots at moderate ISO, so that the "quality" is still there. In the winter time, the light lost might make the converter useless. And some converters are crappy on most lenses, but occasionally you can find a lens that matches well with the converter, and which will give good to very good results with the TC on it.
 
Just out of curiosity, if you're already thinking of getting one, shouldn't you knowt he answer?

;)

TCs are like any other piece of gear; useful if you have a need for them, a waste of money and space if you don't. Plus: Gives you increased range for less cost and in a smaller form factor. Cons: Loss of IQ and reduced maximum aperture (eg: a 2x TC on a 400mm f2.8 lens will turn it into an 800mm f5.6. This isn't bad, but if you try and strap one on to your 70-300 f4-5.6, then yes, you will get a 600mm lens (effectively), but with a maximum aperture of f11; too dim for AF to work in many situations. My thinking is that unless you have good, fast primes, or REALLY good fast zooms, they're probably not going to justify their cost in results.
 
What lenses are you thinking on using the teleconverter with?

Not only are there issues as outlined above, but teleconverters all have a protruding front element; this physically restricts what lenses it can and cannot mount to as many lenses have a very flush rear element and thus won't be able to physically fit to the teleconverter. Even the Kenko Pro series which have the smallest protrusion whilst retaining good image quality are physically limited (though can fit to a few more lenses than most own brand TCs which tend to have a longer front element protrusion).
 
Oh, sorry OP - got a bit off track there. Like the others have mentioned teleconverters will reduce your IQ somewhat, but more importantly they also reduce the amount of light let into the lens - so really unless you have something in the F/2.8 range to start with a 2x teleconverter probably wouldn't be a good choice - odds are good it will reduce the light so much that the camera wouldn't be able to auto focus with it. It's a common complaint about teleconverters.

The 1.4x would probably be a better option even for something in the F/2.8 range - for example, if you added a 1.4x to a F/2.8 70-200 mm you'll extend your reach to 280 mm at F/4. As Derrel mentioned teleconverters, especially the inexpensive ones, do cause a loss of IQ particularly at the edges, so plan accordingly, shoot wide and be prepared to crop.
 
Thanks guys for the infos. Here is a sampled image. I wonder if you can help me out. I have canon 55-250mm, and I know it is not a high end lens. If I crop it, it gets soft and plenty of noises. It is because of winter season that I get poor lighting. It is the smog or hazy out there. Or, my lens is not good enough, and I need to buy more expensive telephoto lens.
$_MG_8469.jpg
 
tecboy said:
Thanks guys for the infos. Here is a sampled image. I wonder if you can help me out. I have canon 55-250mm, and I know it is not a high end lens. If I crop it, it gets soft and plenty of noises. It is because of winter season that I get poor lighting. It is the smog or hazy out there. Or, my lens is not good enough, and I need to buy more expensive telephoto lens.
Click to expand...

I probably wouldn't recommend a teleconverter for that particular lens. At 250 mm your already at F/5.6 - and at 1.4 you'll be losing an F stop and increasing the IQ issues you already have. I'd probably save the money and instead invest in a good 300 mm or 400 mm zoom lens of some sort instead. I think you'd probably be much happier with the results in the end.
 
Putting a good 1.4 on a really good piece of glass works. Putting a good 1.4 on a kit lens gets you softer images and that would be a waste of money.

Good 1.4 and good glass, anything else is a waste.
 
This web page has a LOT of interesting sample photos, showing how "some" converters suck, others mot so much, and a few are pretty good. I know these are not converters one would use behind a lens and in front of a d-slr body, but they do illustrate some of the typical teleconverter problems, specifically strong color fringing or chromatic aberration, and also just overall softening of detail, and lowered image contrast.

Tele Converter Comparisons

If you want a really GOOD comparison and evaluation of Nikon TC's Brad Hill's got a page where he tests Nikon TC's on HIGH-end glass.

Natural Art Images: Brad Hill: Field Tests: Nikon Series III Teleconverters
 
tirediron said:
Just out of curiosity, if you're already thinking of getting one, shouldn't you knowt he answer?

;)
Click to expand...

Good point. I like to ask stupid question, now. Make better decision, later. :wink:

I look at Tamron teleconvertors, and the prices are tempted. It mentioned some quality issues, so I rather hear from you guys.
 
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