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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 11 Apr 2012 (Wednesday) 14:03
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7D + 400 2.8 + 1.4 or 2x converter will it AF?

 
J.Litton
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Apr 11, 2012 14:03 |  #1

I have been looking for a 500mm so I can upgrade to a big boy lens, but can find any. I was wondering if a 400 2.8 with converter on my 7D would be a good idea since they are more readily available? Auto focus is a must for me though.


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Apr 11, 2012 14:06 |  #2

1.4x teleconverter makes it a f/4

2.0x teleconverter makes it a f/5.6

7D autofocuses with up to f/5.6 max aperture

So it will autofocus with either option. Having never used any of them I don't know how well it will AF.


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zerovision
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Apr 11, 2012 14:09 |  #3

Wouldn't a 400 on a 1.6x 7D make it a 640? if you need the 1.4x the mark III, I have heard, is great and can auto focus just fine. Can you rent the two to give it a test run?


  
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FuturamaJSP
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Apr 11, 2012 14:22 |  #4

uh the crop factor doesn't apply to aperture
so on the 7D it's still f2.8 and the 1.4x II would be just fine. The newer version III works better with the new 400 IS II


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amd ­ is ­ the ­ best
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Apr 11, 2012 14:24 |  #5

FuturamaJSP wrote in post #14248699 (external link)
uh the crop factor doesn't apply to aperture
so on the 7D it's still f2.8

The tele-converter does stop it down though.


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imsellingmyfoot
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Apr 11, 2012 14:27 |  #6

Plus the crop factor isn't really relevant if he only has a crop camera as reference.


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FuturamaJSP
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Apr 11, 2012 14:28 |  #7

I know you have to multiply the f number with 1.4 or 2 with tcs but the previous poster made it sound like the crop factor does matter too and only focuses with the new 1.4 III


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Apr 11, 2012 14:30 |  #8

FuturamaJSP wrote in post #14248730 (external link)
I know you have to multiply the f number with 1.4 or 2 with tcs but the previous poster made it sound like the crop factor does matter too and only focuses with the new 1.4 III

Sorry, I was referencing zerovision's post.


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zerovision
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Apr 11, 2012 14:32 |  #9

FuturamaJSP wrote in post #14248699 (external link)
uh the crop factor doesn't apply to aperture
so on the 7D it's still f2.8 and the 1.4x II would be just fine. The newer version III works better with the new 400 IS II

Could you highlight, for me, where the aperture was an important part of the question from the OP. I only saw the part of their question that asked if it would auto focus. Thanks.


  
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amfoto1
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Apr 11, 2012 14:34 |  #10

zerovision wrote in post #14248638 (external link)
Wouldn't a 400 on a 1.6x 7D make it a 640? if you need the 1.4x the mark III, I have heard, is great and can auto focus just fine. Can you rent the two to give it a test run?

No, sorry, but it's still a 400mm lens, no matter what sensor (or film) format it's on.

On the crop camera, it gives an angle of view that's like what a 640mm would give on "full frame" or 24x36mm format, if such a lens existed. But it's still a 400mm lens and will work the same way as always, with or without teleconverters.

For example, following image was shot with crop sensor camera and 500/4 fitted with a 1.4X II teleconverter...

IMAGE: http://farm8.staticflickr.com/7116/6865952788_9c73545992_b.jpg
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EF 500mm f4 IS lens with 1.4X II teleconverter, f5.6 (i.e., EXIF shows 700mm). EOS 30D camera at ISO 200, 1/1000 shutter speed. Gitzo 1325 tripod with Kirk BH-1 ballhead and Wimberley Sidekick gimbal mount. Avail. light, no flash.

In the EXIF, that records as an effective 700mm f5.6 lens. Not an "896mm" lens (700 x 1.4X).

If it's a 400/2.8 IS Mark II, I might consider the Mark III teleconverters. But if it's an earlier version of that lens (either the "Mark I" or the even older non-IS), I wouldn't spend the extra money for the Mark III teleconverters. The Mark II TCs will be fine.

In fact, I recall seeing in one of Canon's releases that the Mark III TCs are actually designed to slow down AF about 25%, to improve focus accuracy. I dunno if this is true with all lens, though, such as using those TCs with the older lenses. OTOH, if I were using 70-200/2.8 IS Mark II I'd be inclined to want the Mark III teleconverters, at least the 2X since it works so much better with that zoom.

I have used the 1.4X II and 2X II on 135/2, 70-200/2.8, 300/4, 300/2.8 and 500/4, and they are quite good teleconverters.... (though 2X on 500/4 makes it a 1000/8, which won't focus with many EOS cameras... and I generally don't use the 2X on the 70-200 or 135).

The Kenko 1.4X Pro 300 DG or DGX is said to have equal IQ, compared to Canon 1.4X II.

zerovision wrote in post #14248753 (external link)
Could you highlight, for me, where the aperture was an important part of the question from the OP. I only saw the part of their question that asked if it would auto focus. Thanks.

If I understand your question correctly, the effective aperture of the lens + TC is important in order for the camera to be able to autofocus. There's one stop light lost to a 1.4X TC and two stops lost when a 2X is added to a lens. So, for example, the above image shows f5.6, which is the lens' effective largest possible aperture after the 1.4X was added. Canon cameras are rated by lens aperture as to whether or not they'll be able to focus (Canon programs them to turn off AF when the limit is exceeded, tho there are ways to fool it and AF might work, if conditions are good). Most Canon can continue to focus, center AF point only, to f5.6. Only 1-series cameras (and the old EOS-3 film model) can focus with f8, again with the center AF point only.

So an f4 lens with a 1.4X added will AF on any EOS. Add a 2X to that same lens and it won't AF on anything less than a 1-series camera.

OP asked about an f2.8 lens and seemed to primarily concerned about whether or not it would still be able to focus with the teleconverters.... Which it will be able to do on any EOS with either 1.4X or 2X. With the latter TC it will be center AF point only on any of the cameras other than a 1-series.

The crop factor of the camera might seem like a teleconverter at times... but it doesn't change the lens' focal lenght or it's effective aperture at all, and so it doesn't change the camera's ability for AF. An f2.8 lens is still an f2.8 lens, whether it's on a 7D or a 5D model. Sometimes crop cameras are referred to as "free teleconveters" for this reason, though that just confuses things a bit.

OP, you also might want to know... the 400/2.8 is a beast... it's bigger and heavier than the 500/4 and the 800/5.6. It's not quite as big/heavy as the 600/4, but close. The 400/2.8 is an incredible lens, though. Heck, they all are!


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FuturamaJSP
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Apr 11, 2012 14:35 |  #11

lol I guess I made a huge mess here. I was telling mr amd is the best that I am disagreeing with what mr zerovision said :D


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Apr 11, 2012 19:50 |  #12

amfoto1 wrote in post #14248767 (external link)
It's not quite as big/heavy as the 600/4, but close. The 400/2.8 is an incredible lens, though. Heck, they all are!

The 400 2.8 IS is actually heavier than the 600 f4 IS by 10 grams.

http://www.canon.com …oto/ef_400_28li​s_usm.html (external link)

http://www.canon.com …hoto/ef_600_4li​s_usm.html (external link)


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J.Litton
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Apr 11, 2012 20:08 |  #13

liquidstone wrote in post #14250461 (external link)
The 400 2.8 IS is actually heavier than the 600 f4 IS by 10 grams.

http://www.canon.com …oto/ef_400_28li​s_usm.html (external link)

http://www.canon.com …hoto/ef_600_4li​s_usm.html (external link)

Wow really? Heck with that then, I'd rather have the 600


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liquidstone
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Apr 12, 2012 02:25 |  #14

J.Litton wrote in post #14248618 (external link)
I have been looking for a 500mm so I can upgrade to a big boy lens, but can find any. I was wondering if a 400 2.8 with converter on my 7D would be a good idea since they are more readily available? Auto focus is a must for me though.

7D + 400 2.8 IS + 1.4x TC = still very fast AF, good enough to catch fast BIFs.

7D + 400 2.8 IS + 2x TC = slowish AF, still great for static subjects but barely able to catch BIFs.


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jdavis37
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May 11, 2012 10:12 |  #15

liquidstone wrote in post #14251908 (external link)
7D + 400 2.8 IS + 1.4x TC = still very fast AF, good enough to catch fast BIFs.

7D + 400 2.8 IS + 2x TC = slowish AF, still great for static subjects but barely able to catch BIFs.

Romy,

Are you using the 400 F2.8 IS I or II? I just rented a 5D3 for a week ( and D800) and absolutely fell in love with 5D3. Opened up my world to where ISo almost didn't matter.

While my current 300F2.8IS + TC's worked well I am considering bigger glass and trying to decide between 500F4 and 400F2.8, both new versions for the weight aspects. If I keep the 300 f2.8 I'll buy 500F4. But new 400 f2.8 is tempting given with TC it becomes 560 f4. 300mm is short reach wise for shooting songbirds at 15 to 25 feet. If the new 400 f2.8 + TC performs closely to 500 bare it may make more sense for me to sell my 300 and buy the 400. Thx John




  
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