The focus issue may need some clarification. When Nikon talks about AF working, they are referring to the lens wide open and not your aperture. The Nikon system uses a wide open aperture for AF, then stops down when the shutter is depressed. That's why the DOF preview button is important. So when you are talking about AF working at f/8 on new camera bodies, it is looking at the lens and teleconverter wide open regardless of your aperture setting.

With a variable aperture lens like a 70-300 f/4.5-5.6 VR the f/5.6 aperture applies to the long end of the zoom - the place where you want more reach. So losing a full stop with a 1.4 teleconverter puts you at f/8 - an area where focus is only reliable with a few of the newest cameras. So even if you chose the Kenko teleconverter which will physically fit, you are at the limit of practical use.

The other thing to keep in mind is that not all AF sensors are the same. The center sensor is the one that produces f/8 AF. The adjoining cross type sensors produce AF at f/5.6. And the remainder AF at f/4. So if you want to try a teleconverter, you are probably going to want to use the center AF sensor. That is one reason why many of us use the back button (AF-On) to focus - so we can focus and recompose quickly. Also keep in mind focus reliability is not as good as you move away from the center sensor. You will get more images with missed focus and a wider range of AF error.

Many of the zoom lenses are not as sharp at the maximum zoom or long distances as they are in the sweet spot. But when you are using a teleconverter, you are often at maximum zoom - so of course the images are going to be softer. Add the normal image degradation of a teleconverter, and you end up with soft images unless your technique and conditions are optimal.

Finally - a teleconverter is going to reduce aperture and extend effective focal length. The longer focal length means you need a faster shutter speed to freeze any vibration or movement, and you need to offset the smaller aperture. So in practice you need enough light to add two stops to whatever you had without a teleconverter. This is true for all lenses - even those that accept teleconverters - and is part of why teleconverters are not used more often.

So I agree completely with the other posts. The teleconverter does not physically fit, AF is not as good or non-existant, you need more light, and image quality drops. You can overcome the physical fit with the Kenko Pro teleconverter, but the other factors remain.

I have the Kenko teleconverter and almost never use it. It is the most useless piece of equipment I own not because it is a bad teleconverter - its just the occasions when I have used it produce sharp images less than 10% of the time. That's too unreliable to be useful. I'm better off living with the constraints of the situation and gear, and working on techniques to get closer.

If you are on a tight budget with medium consumer lenses, the 70-300 ED (not VR) version is available used for around $175. It's a pretty good lens that has been around a long time. While not as good as the newest version, it is better than trying to turn a shorter zoom into something its not.

to specify Garteth post - most current bodies - from d200 can (in good light) focus with f8 or smaller (officially only d4, d800 and d600), though the focusing speed (AF tracking) is slower. what does it mean to TC users. basically, all f4 lenses can be used with TC20. all f2.8 lenses can be coupled with TC20 and TC14 - this option is also not supported by Nikon and requires TC trimming (I would say it's advance use of TC's).

wow!this is a great info Gareth...& i am totally agree with you dude.

Anytime I've considered buying a particular TC to use with a particular lens, I always send Nikon Tech an email and give them the model numbers and ask them what they think; They have always been pretty good about answering me.

A very lengthy and informative article on this topic can be found on Lens Rentals site, written by in-house guru Roger. I can't put the link here because I can never remember whether they're a sponsor, so you'll have to Google it. Sevencrossing does a good job of summarizing the issue though.

I will warn against trying ones that aren't on the list...I would make certain they will work. You will scratch the rear element on your lens by say putting the 18-200 on a teleconverter.

So two factor...light loss as mentioned and space between the rear element. General rule...constant F2.8 to use any of them. Constant F4 is decent with 1.4 and 1.7, but too much loss at 2.0. I don't know of any variable aperture lenses that are compatible, but I haven't looked into it much.

Teleconverters reduce the aperture. A f2.8 lens with x 2 converter becomes f 5.6

The smaller the aperture the slower the auto focus

The auto focus does not work well below a certain aperture, so for example the x 2 only works well if the main lens is f2.8 or wider, this rules out all "consumer" zooms
leaving you with the 70-200 f 2.8

If you have the 200-400 f4 , Nikon, say auto focus will only work with x1.4 but people do use this lens with the x 2, although the focus may be sluggish

the latest Nikon D800 and D4 are ment to have better auto focus at smaller apertures

remember autofocus happens with the lens wide open ,

there needs to be enough space for it to fit for one thing. i.e. the back element is far enough forward in the lens for the tc to slot in behind it.

then there are issues of aperture for af, which nikon doesn't over commit itself to. they don't want people complaining when it doesn't af, they'll just say they never said it did. that doesn't necessarily mean it wont though.

What determines teleconverter - lens compatibility?

Looking at the "official" Nikon list, not that many lens are compatible. However, I keep seeing comments about various lens not on Nikon's list being used successfully with a TC.

Is Nikon's official list a marketing effort to keep people from using the TCs except with the most expensive lens, or is there something else going on here?

Intuitively at least, I would think that an IF lens would stand the most chance of compatibility, as nothing external moves...

Can someone please clarify?

I just shot my first serious event this past weekend with my 70-200 VR2 and the TC2iii.
Here is one pic of it in action. I did not notice any degradation of image quality, even wide open at f/5.6. Though I still stopped down some to f/7.1 for some shots as I had enough light. I love the combo.

The rest of the photos are in a gallery at my site.

scoobysmak said:
The DX crop shouldn't affect AF performance, its just a bonus if your looking for more reach. I do not expect zippy but just telling what I found, I just tried to help.

I had the same experience.

I'm not sure what the technical reasons are, but TC's do seem to perform a bit slower on DX than with FX. Not much though. I notice it, but it has to be a very fast moving object like birds, animals, etc. It could just be tracking an object at (w TC1.7 & 70-200mm -bright light- f8 @1/1000) 300 vs 510 is going to be more difficult at the 510 that DX creates with a TC1.7. The TC20 seemed much slower and that is why I choose the 1.7 as well.

I spoke to others that experienced that with DX as well but that was before the new AF motor/design in the D7000 which seems to be about the same as the D300/D700 (shared AF design) and much better than the D200, D5xxx series. I also thought the D700 was faster compared to the D300 even though they shared the same AF design.

Either way, I think there it says something more about the AF designs than the TCs performance or particular glass you attach it too.

connie64 said:
I was looking more for the "median" of the lens i guess

I have no idea what is meant by that statement.

Well I know that, but I was not worried about testing a TC. I was more worried about learning a new camera that I had not used before. The DX crop shouldn't affect AF performance, its just a bonus if your looking for more reach. I do not expect zippy but just telling what I found, I just tried to help.

So far the need for a TC-20 III has not come up again for me to test one out. If I ever do again I will test all aspects.

I will do a FF and DX test with the 70-200 and 400mm with both TC's along with some day and night testing on both. Both would have the same subject(s), one close and one distant, the only draw back is a possible sunrise/sunset shot may not have the exact same lighting if I am not fast enough changing out gear.

scoobysmak

you should have tested the lens combos on the same camera, for testing purposes.

both combinations on the D700 and then on the D7000 for camera test puroses and lens test.

test of the lenses on different cameras are not valid for lens evaluations.

also, on the D7000 a 400mm f2.8 X TC20 will give you 800mm @ 5.6 x 1.5 =1200mm @5.6

and you expect zippy AF performance?

Well my experince with the TC-17 is I have one, I rented the TC-20 III once.

This was not a fair test but here is my set up and results:

Camera 1: D700, TC-17II, 70-200mm VR2
Camera 2: D7000, TC-20III, 400mm VR (2)-I think this is the only 400mm with VR

The D700 locked on to the subject right away, the D7000 hunted for a moment. The cameras were less than 10 ft apart. This was done at the same time of day, aprox 8 am in June, location FL coast, extreme overcast.

I had not used either the D7000 or the 400mm before that point so a learning curve occurred. I have used the D7000 and the 400mm/TC-17 combo since then and still think the TC-20 III would hunt more than my TC-17 does in low light but with either I dont really see a difference in quality so long as you have good technique.

If I ever have the need to use the TC-20 III again I will test it a little better, but at the moment I was still learning other things so a TC wasn't my primary problem.

hmmm interesting thoughts... I was looking more for the "median" of the lens i guess

I do not have a TC-17 to compare and I try to avoid using the TC-20E III as much as possible but there are cases when 200 mm is just not enough and adding a 7 pound 200-400 mm to my already overweight setup is not an option. In those cases, being able to go 400 mm for a little weight and portability cost becomes a true savior and I rarely endup shooting at or below 340 mm, to the contrary, I often whish to be able to go beyond 400mm.

I also use the TC-20 a lot with the 105mm macro.

Another vote for the TC-20E III but if posible, for best IQ, stop down to f8

I have the TC-17E and love it. I used the older 2x I & II and I thought they worked well and never saw any issues and everyone seems to love the III.

The only thing with 1.7 and much more so with the 2.0 converters is when light drops and you are stopped down, AF starts to hunt and hand shake comes into play quickly. No big surprise, but many claim to have soft TCs when actually they are trying to handhold below 1/300 & 1/450 on DX and think every image will be sharp.

I am in the same boat. Looking to find the right TC for my 70 - 200 VR2 2.8. I have a D90. The combo makes very sharp pics as is.

Thank You

i've been using TC-20E III for a while and can say that it's amazing. there's no IQ losswhich is really important.

If someone needs to discuss why a thread was closed then please contact me via PM or email otherwise those post will be deleted as per forum rules.

You will also want a wide angle for scenery.

I would pay a lot of attention to Thom Hogan's advice here in these discussions. I have seen the best results under these conditions with the 200-400 Nikkor. The problem is on safari you are shooting at a distance which for me is not how I often shoot as i am used to being able to get closer. On safari I find that you are going to be shooting at a distance and almost always in challenging lighting and the 200-400 is the way to go and renting it with the usual insurance package is the way to go. You will need the DX 1.5 multiplier effect. Lucky you are not facing FX issues in this case. I have been there and done that with D300 and seen results from D300s that prove this can work. I do think you will find that 300mm is almost the minimum focal length you will use. I m not a 100-500mm fan. Be advised the 200-400 is a big rig. If you had the freedom to get a little closer the 70-300VR Nikkor would be awesome but you will find most safari photo opportunities to be long distance.

The 200-400 reach isn't much difference than the 120-340 I get with the 70-200 with 1.7 but I also lost a stop with my setup as the best it can get is f4.8. That extra stop would have been really helpful as we seemed to see the most on evening game drives when the light was pretty low. I left the TC on the 70-200 the whole time, but I had a D40 with an 18-200 next to me just in case I needed a wider shot. 80% of my pics (3300 or so) were with the D90/70-200/1.7 setup. I took another 700 on the D40 with the wider angle. If I had time for sunsets, panos, and whatnot, I put the 18-200 on the D90 just for the quality and iso performance bump.

Because I am a US expat in the Middle East, I did not have reasonable rental options, so I went with a setup I can actually afford. I already had the 70-200 and D90 for sports like high school football and basketball and bought the 1.7x tele as a refurb for about $300 with plans to someday go to Africa. I knew I would never be able to justify $5000 for glass as an amateur photographer. If I was going to from the the states, I would have rented an FX camera and the 200-400 or maybe even the 300 2.8 with a TC. It would have cost me close a $1000 I guess for the rentals, but better than the 10K the setup would have cost.

The safari as a whole was great, I am working on building a website with a day-by-day blog and pics and will post it here when it is finished. I think if I do it again, which I may next summer, I may go somewhere not as restrictive. In Kenya they are very strict about not leaving paths to follow animals and you are not supposed to get within 20 meters. We were much closer many times and the animals did not seem to mind. You are allowed to leave the path for the big 5 but the game wardens in Masai Mara kept a pretty keen eye about getting too close or following. One morning we came upon a pride of lions with cubs, but I couldn't get a shot of the cubs because the grass was too high. The game wardens in a truck watched us for over an hour to make sure we didn't drive out to get closer.

i may try South Africa or Botswana next year on a more rugged trip that involves camps (Kenya was all nice lodges with 4 course meals) and following the animals on hunts. That might make for some much better photo ops and more excitement. A safari was the #1 thing on my bucket list (I am only 29) so I did get to mark that off at least.

thanks for sharing Your pictures with us Victor, You have really some nice gems in Your collection. Apart from that I would like to thank You for showing all of us, that You don't need the newest, coolest camera to capture great snaps.

BTW:
how did You found Your new sigma, was it fast enough?