Teleconverters, TC-20 EIII and 200-500mm no autofocus? Experiences wanted.

In the teleconverter compatibility chart that Nikon publishes, they describe the combination of the 200-500mm lens and the 1.7x and 2.0x TC-17 and TC-20 (EII and EIII) as not being autofocus capable.

Based on some reading I've been doing, Nikon apparently doesn't guarantee autofocus to work with some combinations of teleconverters and lenses only because AF requires a certain amount of lighting to work well.

Well, I'm not having any issues with AF working in a lamp-lit room down to or below F22 with the lenses I currently have on hand.

So I'm wondering, is the TC17 or TC20-EIII REALLY completely not AF-capable when used with the 200-500, or are they just covering their backsides by saying that they don't expect it to work?

I have the TC14-EII which IS rated as fully functional with the 200-500. And while I expect to be glad for the extra range it gives me (700mm is nothing to sneeze at), I just know that if a 2x teleconverter will work with this lens, including autofocus under daylight conditions, then I will save up for one.

So, if you have this lens and have tried it with a TC-17 or 20 (EII or EIII), please report your findings with regard to autofocus functionality and performance.

D200freak said:

Well, I'm not having any issues with AF working in a lamp-lit room down to or below F22 with the lenses I currently have on hand.

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I'm curious how you are able to accomplish focusing while at f/22 ? With which lens and procedure?

I assume you are aware that SLR lens are always held at wide open aperture for benefit of the brighter viewfinder and focus when wide open, so we can see it and AF can work. Lenses only stop down to the selected setting when the shutter button activates the actual mirror rise and shutter activation. It is not focusing then, the focus system is in the viewfinder (and the mirror is up).

This wide open maximum aperture is the issue. A few of the Nikon cameras (including the D800 family) can auto focus at f/8, meaning maximum aperture. Or rather, 11 of the 51 sensors can claim f/8. The other DSLR models say they can focus at f/5.6. This means the maximum wide open aperture, which is used for viewfinder and focusing.

The 1.4x TC increases fstop number by 1 stop. The 1.7x by 1.5x stop, and the 2x by 2 stops. The 200-500 is a f/5.6 lens, and so adding 1.5 or 2 stops exceeds f/8 in the wide open position. This is the meaning of Nikons warning. I don't think their "AF not possible" means AF is absolutely 100% totally impossible past f/8, but they are saying don't call them when there is any issue. I think they consider that you have been warned. But f/5.6 with TC 1.7 is only half a stop past f/8, it probably might work sometimes, on a D810.

I have a TC-17, but my lenses that accept it are f/2.8 lenses. I have a Tamron 150-600 f/5-6.3, but I'm not going to put the TC on it. Not sure it would even mount.

I haven't had any AF issues using my 1.4 vII TC with the 200-500. I haven't tried my 1.7 TC yet.

480sparky said:

I haven't had any AF issues using my 1.4 vII TC with the 200-500. I haven't tried my 1.7 TC yet.

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f/5.6*1.4 = 7.84 which should focus with the newer cams but *1.7 = 9.52 or *2.0 = 11.2 are both beyond their capabilities.

The 2.0 on my 70-300mm was a no-go. They only hunted.

Ability to focus has nothing to do with your chosen aperture, it has to do with the minimum aperture of the lens and the camera's ability to focus at that aperture. As J-See pointed out, the f5.6 minimum aperture is probably fine for your camera by itself, but with the converters that minimum aperture gets multiplied too, and the values of f9.52 and f11.2 are higher than the min aperture AF rating of all their cameras. That's not to say that it wouldn't work on a bright day with a well defined subject, but it wouldn't be something you could count on.

I don't yet have my 200-500 in my hands. It's supposed to arrive at the store today and I pick it up when it arrives.

I checked AF on my D800 using my 24-85mm at every setting down to F/22. It never missed, and that was in a room illuminated by a single 60 watt light bulb. So if the camera isn't supposed to have reliable AF below F/8, then I am pleased to see that my camera is an overachiever.

I do know that the TC14EII is rated as fully compatible with AF functionality with the 200-500. And I have that teleconverter.

But knowing myself, I know that if the TC17 or TC20 actually do work with it and allow AF to work, at least in daytime conditions, then I'll get one. But AF is pretty important to me as I'll be using the 200-500 at racetracks and airshows, where autofocus needs to be both fast and accurate and I will take all the zoom range I can get. Thus the hope that the TC20 will suit my requirements.

D200freak said:

I don't yet have my 200-500 in my hands. It's supposed to arrive at the store today and I pick it up when it arrives.

I checked AF on my D800 using my 24-85mm at every setting down to F/22. It never missed, and that was in a room illuminated by a single 60 watt light bulb. So if the camera isn't supposed to have reliable AF below F/8, then I am pleased to see that my camera is an overachiever.

I do know that the TC14EII is rated as fully compatible with AF functionality with the 200-500. And I have that teleconverter.

But knowing myself, I know that if the TC17 or TC20 actually do work with it and allow AF to work, at least in daytime conditions, then I'll get one. But AF is pretty important to me as I'll be using the 200-500 at racetracks and airshows, where autofocus needs to be both fast and accurate and I will take all the zoom range I can get. Thus the hope that the TC20 will suit my requirements.

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It doesn't matter what aperture you set the lens to to take the photo with. What matters is what the maximum aperture is before you take it.

Most bodies will AF down to 5.6 or 8, some of the higher-end one will do just fine at 11. The AF module sits below the mirror in front of the shutter. It uses the light coming in through the lens (which, at this point is at maximum aperture regardless of what you've set it at for taking the image). Some of the light passes through the mirror you see inside the camera, and is reflected down with another mirror behind that down to the AF module.

Only when you take the photo does the lens close the aperture blades down to the set aperture. By this point, the AF module won't work because the two mirrors have been moved out and up so light from the lens can be controlled by the shutter. You can use a lens set to f/45 or f/64 or even f/90, and the AF will still use the lens wide-open to function.

Also keep in mind that when you add a TC to your 200-500mm, the quality of your image takes a dive. Not so much with a 1.4 but more with a 1.7 and a serious dive when using a 2.0.

For me the 2.0 performs that poorly I'll try to mod it into a fully functioning extension tube. That way I hopefully get something useful out of my wasted cash.

D200freak said:

I checked AF on my D800 using my 24-85mm at every setting down to F/22. It never missed, and that was in a room illuminated by a single 60 watt light bulb. So if the camera isn't supposed to have reliable AF below F/8, then I am pleased to see that my camera is an overachiever.

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You are not understanding how it works. The camera keeps the lens wide open at all times, for the viewfinder and for focusing, which is aided by the brighter light wide open. You are NOT focusing at f/22, you are focusing with the 28-85mm lens wide open, at f/3.5-4.5.

To better understand, try this. Setup the camera for a f/22 shot, as before. Then while watching through the viewfinder, reach up and press the Depth of Field Preview button, top button at the side of lens, under the shutter button. You will then see the difference in viewing with the lens wide open, and viewing when stopped down to f/22. You can also simply look into the lens as you press the shutter button, and see it stop down to f/22 only for the shutter duration.

For the TC, shooting at f/22 is no problem at all. The lens is wide open for focusing. The wide open aperture being more than f/8 is the problem.

The 24-85mm lens is f/3.5-4.5 wide open. Even if this lens were compatible with TC (it's not), then the TC 1.7 would add 1.5 stops, so that even f/4.5 becomes slightly less than f/8, and still in spec.

But the 200-500 lens is f/5.6, and adding 1.5 stops for 1.7 TC becomes 1/2 stop past f/8, out of spec. So Nikon advises forget it. It could still work sometimes, but difficult AF cases likely fail to focus. You would likely lose some shots. Nikon is advising against this try.

ALL LENSES with a maximum aperture of f/4.8 or more are said to be incompatible with the f/8 limits of AF focusing with the TC-1.7.
For the TC-1.7, this is f/3.3 for camera bodies that can AF at only f/5.6

D200freak said:

I checked AF on my D800 using my 24-85mm at every setting down to F/22. It never missed, and that was in a room illuminated by a single 60 watt light bulb. So if the camera isn't supposed to have reliable AF below F/8, then I am pleased to see that my camera is an overachiever.

I do know that the TC14EII is rated as fully compatible with AF functionality with the 200-500. And I have that teleconverter.
.

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LOL. Read the other comments in this thread. It doesn't meter where the f-stop is set for the shot, it matters what the wide open f-stop is. The TC reduces the effective f-stop as a factor of the magnification of the TC.

The TC14EII will work because it will make the f/5.6 200-500 effectively f/8 300-750. Your camera can still reliably autofocus at f/8. Also, though, be aware that not all of your focus points will work at f/8. According to what I just saw on the Nikon site, there are 11 focus spots that will function at f/8 on the D800.

Nikon | Imaging Products | Still image shooting functions - Nikon D800/D800E

Yeah, I got it. I knew that the aperture is wide open except when actually taking a picture, at which point it snaps to the selected aperture, but I just hadn't thought about it when I posted.

I realize that adding another piece of glass into any optical system is going to be a tradeoff. Some loss of contrast, sharpness, or brightness is inevitable. But there may be times when the tradeoff is affordable.

When my lens arrives, I'll test it with the TC17 and TC20 they have on display, just to satisfy my curiosity.

If it'll AF well under sunny daylight conditions, that is sufficient for me, because it's under those conditions that I'll be wanting to make the most use of the 200-500 and if I had even more reach I'd be glad to have it as long as the image quality is still good enough.

This will be my lens for such activities as automotive racing events and airshows. Long reach and fast, reliable autofocus are of greatest importance, after image quality.

D200freak said:

When my lens arrives, I'll test it with the TC17 and TC20 they have on display, just to satisfy my curiosity.

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I'm guessing the TC 1.7 might still work much of the time with a D800 under good conditions. But manual focus should still work even when it doesn't. It's just that trouble will delay any situation, when your shot may not wait on you.

I used a TC 1.7 with a f/2.8 70-200. It does hurt optical quality a bit, but it still seemed decent enough if stopped down at least a stop or two. The TC is definitely not best when wide open.