davidrb Loc: Half way there on the 45th Parallel

Canon 7D, 100-400mm L II, 2X III converter.
About 1/2 mile away.
f2.8 becomes f5.6 800mm. Guess what? 800mm is f5.6 so no loss of light when compared to the 800mm anyway so not too sure what the light loss issue is.
Here is a link for the 800mm in case there are any confused people.


Where is the 400mm lens mentioned?

Nalu Loc: Southern Arizona

I have seen two references to the 400mm DO II as a f/4.0 400 prime II. I wish people would call it by its proper name.

mwsilvers Loc: Central New Jersey

The Extender 2x III was purchased on a whim for my EF 70-200 f/4 L IS USM. This is a super sharp lens, but with the 2x III maybe one in 10 shots was acceptably sharp on my Canon 7D Mark II. And "acceptably sharp" was still a far cry from what the lens is capable of on its own. I sent it back to B&H. I'm not a birder/wildlife person so I think I can live with the native 200mm.

Haydon

Arthur Morris had much better luck than you....

http://www.birdphotographers.net/forums/showthread.php/75152-Canon-70-200mm-f-2-8-L-IS-II-amp-2X-II-Teleconverter-Report

Admittedly it's an aged article but this "Canon Explorer of Light" was more than satisfied. I had another article but I was unable to find it. FTR- I only use a 1.4x III. Morris believes that bird photographers who use long white glass should have both teleconverters. I've used the 1.4x III on my Canon 500 F4L and a Canon 70-200 2.8L II and there is only a minor hit on quality. I've been reluctant to buy/use/rent a 2x. I think it comes down to variances, technique and what is considered acceptably sharpness.

robertjerl Loc: Corona, California

An article on extender compatibility says that with that lens and extender AF and IS only work on the latest high end bodies, and then center point only. In fact they only named the 1DxII, but since the date of the article the 5DIV and 80D came out with improved AF. Maybe it would AF with those.
So to get sharp images you need to use high shutter speeds and very careful framing to get the center point on the part you want sharp, or just go to manual focus.

Haydon

Micro-adjusting for that combination might be a necessity as well.

mwsilvers Loc: Central New Jersey

At f/8 my 7D2 can AF with the center point and 4 assist points. I used it on a tripod with shutter speeds of over a thousand, shooting static subjects on a bright sunny day. The Extender 2x III is said to work well with the 70-200 f/2.8 L IS USM so I gave it a shot on my f/4 IS version to see if I could achieve similar results, but was very disappointed. I frankly did not have high expectations, and perhaps with more practice my results might have improved somewhat, but in the end, with that lens I believe the comprises would have been too great for the occasional use of a $429 Extender.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

There is no way of maintaining IQ with a 2X. The only advantage of that extender is that it gets you closer, but at a great cost. It is usually never worth the compromise.

markngolf Loc: Bridgewater, NJ

Regis Tolbert (UHH member) shoots that combo frequently. He does shoot with Canon 5DSR. you may want to contact him.
http://www.uglyhedgehog.com/t-430902-1.html. I shoot with the 2x III mounted on my Canon 5D MIII and 7D MII with a Canon 70 - 200 mm F/2.8 II.
Mark

Notorious T.O.D. Loc: Harrisburg, North Carolina

OP should just buy one from B&H use it a lot and if not happy return it before 30 days.

Best,
Todd Ferguson

wilfred

Newer verses older. My experience actually compairing the older with the newer was no difference in quality. I was told by canon tech that the newer converters (serieslll) would be better optically on the series ll lenses, but not so with the older (non series ll), and that the series lll converters would give any added edge to the newer (series ll) lenses.
I found this to be true, except for my 800 5.6. I found the newer series lll converter to give a slightly sharper image, with the newer converter. This is however the only lens i found this to be true for.
So my advice is to buy the newer more expensive series lll only if you need it for a series ll lens, or in my case the 800 5.6. Otherwise continue to use the series ll converters with the older (non series ll) lenses. Light loss same regardless.

mwsilvers Loc: Central New Jersey

Yes, its been documented that the 2X Extender does seem to work well with some long primes like the his super 400 f/4, but its more problematic on some shorter focal lengths and zooms. Your 70-200 f/2.8 L IS USM does seem to work acceptably with it, but with my 70-200 f/4 IS version it was a real struggle to get anywhere near acceptable sharpness. I don't want to have to fight the equipment to get acceptable results. If I think I need a full time lens for birding or wildlife I'll consider getting the spectacular EF 100-400 L II.

amfoto1 Loc: San Jose, Calif. USA

Which 400mm Mark II? Canon makes two: EF 400/2.8L II IS USM and a 400/4 DO II IS USM.

I don't have either lens... The "Mark III" teleconverters supposedly works slightly better on the f2.8 lens, than on the DO. But the latter is still very good.

Compare either lens with and without 1.4X and 2X, and against each other for yourself: http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=962&Camera=453&Sample=0&FLI=1&API=2&LensComp=962&CameraComp=453&SampleComp=0&FLIComp=0&APIComp=0

Optically, there doesn't seem to be a whole lot of difference between the Canon 1.4X II and 1.4X III.

The 2X III was a bigger improvement over earlier versions in terms of image quality (but IMO the II really works quite well on some lenses).

Something I found a bit surprising..... When first introduced Canon's announcement about the III teleconverters mentioned that the new extenders' electronics were designed to slow down auto focus by about 25%. Maybe this was to promote accuracy, since the lens + extender would result in shallower depth of field.

I use both 1.4X II and 2X II. The latter I mostly just use on 300/2.8 and 500/4 primes, where it works great. The 1.4X I use a lot more often, with those same lenses as well as a number of others incl. 135/2, 300/4 and 70-200. Recently got the 100-400 II and plan to experiment using the 1.4X II on it, too.

I have no plans to "upgrade" to the 1.4X III, because I just don't see much or any difference compared to the II version.

While it works fine on my 300 and 500mm primes, I definitely won't use the 2X II on any zooms. Haven't found a zoom + 2X II combo that gives me images I'm happy with. Some people feel the EF 70-200/2.8L IS "Mark II" with the 2X III works very well... (much better than the combo of the earlier versions of each). But I wouldn't expect it to come close to the quality of a 400mm prime and won't be running out to buy it because other lenses in my kit handle the focal length.

wotsmith Loc: Nashville TN

I use 2X all the time for bird photography. Usually with the 1DX with a 600mm f4 prime, occasionally with a 300mm f2.8 when I am lending my 600 to my son-in-law. It focuses very quickly and very well. Here are three shots with the 600 and 2x handheld from a boat. I don't see any loss of quality, do you? What I did not realize when I bought my 600 was that better technique was needed to use that lens. Then when I added the 2X even better technique. When I mention technique, I am not referring to better tripods, as I hand hold most all my shots. How do you stabilize the lens, how do you squeeze off the shutter, etc. I think that most of the comments about loss of quality are related to poor technique, not related to the teleconverter. I do suspect that the higher end bodies, focus better and faster at lower light. Before you accept that using a teleconverter gives lower quality, check out Art Morris' website at birdsasart.com and see his fabulous photos with teleconverters. Which is easier, blame a poor photo on the teleconverter or realize that your technique is not the very best? BTW, I do micro focus each lens and each lens/teleconverter combo, like Art Morris recommends.
Bill

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Nalu Loc: Southern Arizona

One of the sweet things about the 1dxii and 5div is that all AF functions operate at f/8. No limitation to center point. Don't know about upgrades to other bodies.