Teleconverters for G lenses?

[linh__]

I have a Nikkor 70-300mm G lens. Are there teleconverters that are

compatible with G lenses? The Nikon teleconverters seem to only

work for D lenses...what about other brands? Kenko? Tamron?

Quantaray?

[Jerry_]

What camera body are you planning to use?

[alex_lofquist]

You will need a Nikkor TC14E (1.4X), though you may loose AF at the longer settings. (At 300mm its maximum aperture becomes a true f/8.) By the way, your 70-300 is also a "D" lens which conveys the focussing distance to the camera microprocessor. "G" and "E" are two different characteristics, so a lens may have one, both, or neither.

[ilkka_nissila]

The TC-14E is <I>not</I> compatible with the 70-300 G. You need an AF-S or AF-I lens to use the E series teleconverters. It's also possible to modify the converter to work with some other lenses, I don't know if it would work with the lens you're talking about.

<p>

TC-14E definitely won't support AF with non-AF-S lenses.

<p>

There may be third-party teleconverters which work with your lens and they may also support AF, but don't expect very good image quality.

[roto]

I've got a Kenko PRO 1.4x TC and I'm quite happy with it. I don't have the Nikon equivalent (only the TC20E II) so I can't make a comparison, however the quality loss with the 70-200/2.8 VR is really minimal.

 

The TC is compatible with all AF and AF-S Nikkors, thus you can use it with your lens, but I wouldn't expect great results when coupled with the 70-300.

[jim_gifford]

Nikon is no help for you here. Your best bet is the Kenko Pro teleconverters.

 

Nikon's older teleconverters like the TC-14A will work okay with lenses up through Af and AF-D models, although one loses the autofocus capability once the teleconverter is attached.

 

Unfortunately, if you mount such a teleconverter to a G-series lens you lose the ability to control the aperture, since the older teleconverters are "AIS" type and do not pass any electronic chitchat back and forth between camera and lens. So with a G-series lens attached to a TC-14A, for example, you'd have a lens with 140 percent of its nominal focal length but the lens would be at its miniumum (smallest) aperture... plus a stop... with no way to adjust that.

 

Ick.

 

So go shop at Kenko.

 

I swear, Nikon marketing is so THICK sometimes. The company should at least buy the rights to the Kenko Pro series and rebadge them with a NIkkor label to be able to PRETEND to care about folks who don't buy zillion-dollar telephotos.

 

Sorry, I was just ranting there for a moment. Go buy the Kenko. And yes, you'll lose some image quality, and yes, you might have a lot of trouble autofocusing unless you're working in wonderful sunny conditions... but it will do what you want, and it will be perfectly acceptable.

 

Have fun,

[ilkka_nissila]

I think Nikon's point for not producing AF teleconverters for AF lenses is that it would introduce additional mechanical slack in the system, and be very slow to focus and probably inaccurate. As for the G lens which isn't AF-S, well, I doubt it would benefit from a TC. I would think Nikon has a lowest acceptable image quality limit of a sorts. The teleconverter compatibility table is readily available in brochures and on the Internet, it's not some secret that is revealed only after purchase.

[john_n._wall]

I agree that Nikon is very short-sighted to avoid upgrading its TCs, so I concur with the recommendation to go Kenko. Based on my own experience and on all the evidence from people who have tested the Kenko PRO TCs with care and good technique, I have to conclude that they are superb. The 1.4x involves practically no loss of quality at all and the 2x produces a slight softening of image quality and a bit of flattening in contrast but the result is still excellent images.

[joseph_wisniewski]

The Kenko PRO-300 will work very well on the pretty sharp (but underrated) 70-300, just as it does on the 70-210 f4-5.6 AF Nikkor. There were a lot of ammusing comments by people who have obviously never tried such things.

 

There won't be problems with "mechanical slack", it won't be "inaccurate" and there isn't a "lowest acceptable image quality limit of sorts". AF will be a bit slower, because the teleconverter incorporates reduction gearing to deliberatly slow the AF. If AF isn't slowed down when using teleconverters, the reduced DOF causese overshooting.

 

The 1.4x Kenko has a front element that provides as much clearance as the SLR mirror itself does, and can mount to virtually any lens, although it works better on telephotos.

[alex_lofquist]

You're right! I just looked it up to be sure. I guess that leaves only the Kenko.

[ilkka_nissila]

Joseph, there is looseness in the the camera and lens AF coupling even with a Nikon camera and an AF Nikkor lens (if the body motor is used) - no TC is needed to introduce this. This is why the "screwdriver" AF hunts a little before stopping down, while AF-S lenses usually stop instantly. The body cam position is not 1:1 mapped to the lens focusing distance, as there is hysteresis. Now, my guess is that this hunting tendency increases if a TC is used since the number of mechanical couplings with finite tolerances increases by one. I hope you realize that there is no way to implement this type of a thing without double hysteresis in which rotation of the body motor momentarily has no effect on the lens focusing EITHER WAY.

 

It is true that I haven't used a Kenko TC, but the laws of physics have a tendency of changing very slowly (over billions of years, even though many won't learn them even in that time) and thus I dared to comment on why Nikon doesn't make comparable things. The inaccuracy part is related to the additional hysteresis, and the fact that the effective aperture decreases to f/8, which increases the DOF and makes AF less accurate.

 

As far as optical quality of a 70-300 with a 1.4 TC goes, well, I'm glad you like it. I have owned exactly two lenses (and those are primes) which give acceptable image quality with a TC. I was only trying to suggest why there is little incentive for Nikon to introduce a TC for this lens. The Kenko exists, so it's there for those who need it.

[linh__]

Wow!! Thanks all for the great responses! I really appreciate it.

[joseph_wisniewski]

Ilkka is correct about three things. First, as he says, he is guessing. Second, the laws of physics do not change noticibly in human lifetimes. Third, as he says, he has no actual experience with any of the lenses or teleconverters under discussion.

 

So, the physics involved in his "looseness" is actually called backlash, and it has been well understood for centuries, and compensated for in electronic control systems for decades. It won't affect the speed of a competently designed control system. It is not the reason for "hunting".

 

AF-S lenses focus faster because, in general, they are faster lenses (wider light cone for the control system) and because each motor is exactly tuned for each lens. There is no "one size fits all" compromise in the control system that might overdrive a lightweight lens while moving a large one more slowly.

 

A conservative 1.4x teleconverter will only take an f4 zoom, such as the one described, down to f5.6, and AF should still operate.