What exactly is so good about the 7D's AF?

chris321

chris321

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Chris
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O.K, I don't mean to insult anyone or their camera, please bear with me here :D. I've been looking at getting a body to be a dedicated sports/action/wildlife one. My principal 2 requirements are:

  • Reasonably high MP for cropping (18MP combined with the x1.6 crop factor sounds spot on)
  • 720/60p video mode, as I'm thinking of getting into video properly, and what I'll be shooting would benefit from slowww-mo.

So this basically brings me to the 550D / 60D / 7D debate than many people are finding themselves in. I've almost ruled out the 550D, as I found such a small body to be quite uncomfortable to hold when coupled to a large lens. Which leaves the 60D and 7D.

The extra fps doesn't really concern me too much, as impressive as it is shooting at 8fps, I'll just burn through memory cards and still not have any more keepers (been there, tried it, had to delete a whole load more pictures :D), so as far as I can tell, it pretty much comes down to the autofocus.

Everywhere I look, I get the same thing saying "the 7D's autofocus is much better", but no-one ever seems to clarify or quantify this. O.K, so it's got 19 AF points, but I only really ever use the centre one anyway.

So, is the 7D's AF actually better, if given the same lens (f/2.8 or better), only using the centre point than a 60D, or a 5DII for that matter? Or is it just a case of getting more choice, more af points, etc?

Sorry this is so long-winded, hope some of you managed to get this far :thumbs:

Chris
 
Does the 7D not use a very similar version of AF as the Mk4? Im sure ive read that on here and the net.
 
Because its got many modes, look on the B&H site, there are a set of three videos there on the 7D, presented by a guy from Canon. granted it is a sales pitch but does explain the camera quite well from what I can see.

Although you may use centre point it has a setting where it will use the centre point, but if it fails to gain focus on that it will look at the points surrounding the centre one to see if it can grab focus on one of these.

It has spot focus points, essentially a smaller version of your existing ones , the idea being it would let you focus on something through small gaps (imagine trying to shoot between branches of a tree to capture a bird).

It also has a tracking - you pick a focus point to start on, it will focus on this but as the subject moves it will move focus points with the subject, the video mentioned above has a person walking from right to left through the frame, focus starts on the right hand focus point and moves with the subject to the centre and then eventually to the left hand focus point.

Its also got settings you can adjust to delay the shutter whilst re-focussing, the idea being you may want to let it completely focus before taking your shot. There is another setting to do with the delay between switching focus points.

Lots of others bits and bobs with it too, best to go dig out those videos.

I don't think any of these features are exclusive to Canon or the 7D, but from what I read there aren't many (any?) cameras that have all of these features, especially in a crop body.

Compared to the 60D you've also got microadjust and built in flash triggering. Theres also something about focus whilst in video mode ?
 
As mentioned the 7D has a very sophisticated and configurable focus system, which has been the downfall of many as well :), as a sports/Wildlife camera it is hard to beat. I would point out however that video focussing is erm... useless and manual focus is the way to go as can be deduced from the various follow focus attachments for shooting video, which would also apply to the 60D
 
Euan said:
Does the 7D not use a very similar version of AF as the Mk4? Im sure ive read that on here and the net.
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Not sure, I keep reading that the 7D and 1D's AF mechanisms are similar, but no-one every says how they're similar! Or what the differences are! I WANT NUMBERS :D (shouting not aimed at you, more so Canon and the reviewers :lol:)



Craft said:
Because its got many modes, look on the B&H site, there are a set of three videos there on the 7D, presented by a guy from Canon.....
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Cheers, to be honest I hadn't picked up on all of these more minor points, most reviews are full of just the headlines! I'll definitely have a look at the videos, cheers for letting me know about them :thumbs:



artyman said:
As mentioned the 7D has a very sophisticated and configurable focus system, which has been the downfall of many as well :), as a sports/Wildlife camera it is hard to beat. I would point out however that video focussing is erm... useless and manual focus is the way to go as can be deduced from the various follow focus attachments for shooting video, which would also apply to the 60D
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O.K, I think I might try and find an online version of the manual, and have a read through at all of the little things it does! I wouldn't expect the AF in video mode to be wonderful, I've been practicing the whole 'manual focus' thing recently though for this very reason :)


Hope said:
60D has built in flash triggering too
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Thanks for that!

Chris
 
I've given this thread a thorough clean.

Back on topic please, any personal disagreements can be kept out of this (or any other) thread please. You know who you are :suspect: :nono:
 
7D AF explained - http://www.usa.canon.com/dlc/contro...&articleID=3049&productID=329&articleTypeID=5

Apart from the performance of the AF sensors themselves, don't overlook the customisation options. One that can be of particular importance is the tracking sensitivity - i.e. the delay before the camera goes in search of another target if/when the subject moves away from the chosen AF point. That can be the difference between clinging on to a tricky subject (e.g. BIF) or finding yourself staring at a sharp background with no clue where your subject has gone, or having the camera search blindly in a sea of blue sky.

I know you mention f/2.8 glass, but the 7D has cross type AF sensors throughout for lenses up to f/5.6, making the outer points potentially better on the 7D than the 1D3, (which I also own) when coupled with slower optics such as the 100-400. Then there's also spot AF when you want to snipe perfect focus on the eyeball of a bird between some twigs, and the ability to customise the DOF button to allow instant temporary switching between AI Servo and One Shot mode.

I have no idea of how the capabilities of the 60D or 550D compare, but I really do find the 7D to be very good. Sample and crop (at 1600 ISO)....

20100919_125351_2051_LR.jpg
20100919_125351_2051_LR-2.jpg


and another....
20101229_133331_.JPG
20100618_184327_9675_LR.jpg


last one....
20100429_141422_6777_LR.jpg
20100429_141422_6777_LR-2.jpg
 
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tdodd said:
I have no idea of how the capabilities of the 60D or 550D compare, but I really do find the 7D to be very good.
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Well, the 7D has a separate processor, dedicated to nothing but AF, which both the 550D and 60D lack.
 
5D2 is probably more accurate due to the 6 assist points at the centre lol



chris321 said:
So, is the 7D's AF actually better, if given the same lens (f/2.8 or better), only using the centre point than a 60D, or a 5DII for that matter? Or is it just a case of getting more choice, more af points, etc?

Sorry this is so long-winded, hope some of you managed to get this far :thumbs:

Chris
Click to expand...
 
Oncoming DIF with 7D and 5D2 at equal focal lengths and exposure settings and similar (not identical) Lightroom adjustments ....

20110202_185735_000.jpg


crops....
20110202_185802_000.jpg
 
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My take on those images: the 7D is noisier than the 5DII at ISO400
 
arad85 said:
My take on those images: the 7D is noisier than the 5DII at ISO400
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The23rdman said:
Not exactly news is it?
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A couple of things - I effed up the exposure on both. The 7D shot has had +1 added in Lightroom and the 5D2 shot has had +0.5. That's the difference in the edit adjustments. Both have been sharpened equally (well, the same settings) and NR for both images is at Lightroom defaults. Viewed at 100% the file from the 7D is obviously enlarged far more than that from the 7D. I thought this thread was about AF, not about picking apart image files undergoing differing degrees of enlargement.
 
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