Really that much difference btw d600/6d autofocus system???

Started Sep 22, 2012 | Discussions
ultimoamore Regular Member • Posts: 297
Really that much difference btw d600/6d autofocus system???

I posted this question on a couple of threads, but didn't receive all the answers I was looking for, so here's a new thread about it:

I think what has been criticized the most of the 6d is the autofocus system, compared to the d600.

While it's clear that having all those points in d600 is certainly better, I don't see why people think they are that much better.

(I'm going to talk about performance on paper, since nobody compared in real-world; but the critics come from the specs, so let's talk about those)

d600 has 9 cross point, but they are in the very center of the screen:

http://imaging.nikon.com/lineup/dslr/d600/features02.htm

My understanding is that people (me included) find using 1.4-2.0 lenses with 5D & 5DII hard, since we all rely on focus&recompose, as we don't "trust" the outer points (which are not that "out" anyway).

But I don't see how d600 layout are going to avoid the "focus&recompose" problem.
Or the external, not-cross-points are more accurate than canon's?

Nikon's system looks more expensive, but I don't see it so appealing to me (at least for the type of photography I do???)

In fact, I like canon's layout more, since outer points are closer to the edges (I don't know if this pict represents the real distance from focus points to the edges):

So to me it looks like the d600 autofocus would be better for actions (where more points are better) but I don't see the added value in avoiding the "focus&recompose" problem...

Canon EOS 5D Canon EOS 5D Mark II Canon EOS 6D Nikon D600
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cs hauser Contributing Member • Posts: 731
Re: Really that much difference btw d600/6d autofocus system???
1

ultimoamore wrote:

In fact, I like canon's layout more, since outer points are closer to the edges (I don't know if this pict represents the real distance from focus points to the edges):

I don't think that is an accurate representation of the AF spread. The spot meter circle shouldn't be that big relative to the entire frame.

ultimoamore wrote:

So to me it looks like the d600 autofocus would be better for actions (where more points are better) but I don't see the added value in avoiding the "focus&recompose" problem...

I agree. It's unfortunate that so many people judge AF systems based on the number of points alone. Having a large number of AF points certainly helps with tracking a moving subject, but it doesn't benefit people who shoot static subjects. Especially if the outer points are not cross-type, as is the case with all current Nikon dSLRs.

People who typically shoot static subjects with a single point? It wouldn't matter if they used a 5D2 or a D700. The advantage of a 51-pt AF system would only manifest itself when tracking moving subjects. When people shoot static subjects, they tend to use the most reliable AF points (cross type). And if all those cross types are bunched in the very center of the frame (like the D600 or D700), then there's no practical advantage to be had over a single-cross type camera (like the 6D or 5D2).

Starkiller Regular Member • Posts: 196
Re: Really that much difference btw d600/6d autofocus system???
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OP ultimoamore Regular Member • Posts: 297
Re: Really that much difference btw d600/6d autofocus system???
1

Starkiller wrote:

Your 6D image is a crop, see:

Yes, you're right; so there's nothing "better" as far as autofocus goes (except maybe the -3ev thing) vs the d600; but, still, I think one has to focus&recompose anyway with the d600. I guess we're focusing on the number of autofocus points too much; the way they're disposed (especially the cross ones) is much more important (this doesn't apply to sports though). And there's nothing in the layout of the d600 that's better than the 6d. I sure wished for at least a 5-cross point system in the 6d....

runefb Contributing Member • Posts: 501
Re: Really that much difference btw d600/6d autofocus system???

No, that cannot be right... the blue line is the viewfinder line. Look at the 1DX below....
Rune

ultimoamore wrote:

Starkiller wrote:

Your 6D image is a crop, see:

Yes, you're right; so there's nothing "better" as far as autofocus goes (except maybe the -3ev thing) vs the d600; but, still, I think one has to focus&recompose anyway with the d600. I guess we're focusing on the number of autofocus points too much; the way they're disposed (especially the cross ones) is much more important (this doesn't apply to sports though). And there's nothing in the layout of the d600 that's better than the 6d. I sure wished for at least a 5-cross point system in the 6d....

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OP ultimoamore Regular Member • Posts: 297
Re: Really that much difference btw d600/6d autofocus system???

runefb wrote:

No, that cannot be right... the blue line is the viewfinder line. Look at the 1DX below....

Sorry, didn't understand your reply...

Craig76 Regular Member • Posts: 255
Re: Really that much difference btw d600/6d autofocus system???

Good analysis of the AF systems. I did something similar by downloading layouts of D600 and 6D AF and layering them in Photoshop. The black dots represent the 6D layout spread, the green the D600.

Both systems cover about the same distance in the frame. The 6D being just a tad wider, but both are clumped in the center. Nikon has more cross type points, but with them all clustered in the center is only better for one use really, action photography.

The Nikon is only sensitive to -1 ev (a step down from the D800's -2 ev), while Canon increased sensitivity to -3 ev.

So, numbers aside there isn't that much difference between the two. It is dissapointing, but switching to Nikon over AF would be kinda pointless. And actually may be a step down compared to the 6D.

I entertained the idea of switching systems, but decided to instead get a Sigma 12-24mm FF lens that I can use NOW on my 60D...then when I get a 6D in 4 or 5 months I'll already have an ultra wide lens for it
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jonrobertp Forum Pro • Posts: 12,856
Re: Really that much difference btw d600/6d autofocus system???
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neither is impressive.

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bobn2
bobn2 Forum Pro • Posts: 53,199
This is the rule
1

a) If Canon has more it definitely is important. The 61 point AF in 1D X and 5DIII is very definitely better than the 51 point AF in D4 and D800.

b) If Nikon has more it is not important. The 51 point AF in the D300s is not better than the 19 point AF in the 7D, nor is the 39 point AF in the D7000.

Therefore the AFs in the 6D and D600 are covered by rule (b). The 6D is definitely better.

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Bob

Craig76 Regular Member • Posts: 255
Nope.... (n/t)
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treepop
treepop Contributing Member • Posts: 691
Re: This is the rule

bobn2 wrote:

a) If Canon has more it definitely is important. The 61 point AF in 1D X and 5DIII is very definitely better than the 51 point AF in D4 and D800.

b) If Nikon has more it is not important. The 51 point AF in the D300s is not better than the 19 point AF in the 7D, nor is the 39 point AF in the D7000.

Therefore the AFs in the 6D and D600 are covered by rule (b). The 6D is definitely better.

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Bob

I must say. I didn't know the Cross type focus points on the D600 were all smushed in the center of the frame. That combined with the -3ev...I gata say...I would rather have the 6D.

Now if the D600 had its cross type focusing spread out, I would definitely lean towards the D600.

So good point Original Poster.
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OP ultimoamore Regular Member • Posts: 297
Re: This is the rule
1

bobn2 wrote:

Therefore the AFs in the 6D and D600 are covered by rule (b). The 6D is definitely better.

What we're trying to say is that the number of points is important for action. The number of outer cross points is important for fast lens (to avoid focus&recompose).

  • d600 and 6d have no outer cross points -> none is "better" for fast lenses

  • d600 has more points -> better for action

  • 6d has more sensitivity in the center point -> better for low light (on paper)

When I saw the number of cross points in d600 I was thinking about a switch... but being in the center doesn't help me with the focus&recompose thing. I don't do action/sports; to me higher sensitivity is better (low light it's what FF are supposed to be good at). So, if I had to choose, I'd choose 6d. But neither camera is "totally" better than the other; they're just different (don't get me wrong; on a lot of other points d600 is better).

Would I pay 200$ more for 8 more cross points, all decentered? YES!!!! It would become the "definitive" FF for me.

x-vision
x-vision Senior Member • Posts: 1,225
Re: Really that much difference btw d600/6d autofocus system???

ultimoamore wrote:

In fact, I like canon's layout more, since outer points are closer to the edges (I don't know if this pict represents the real distance from focus points to the edges):

Nope. Here's the real layout of the 6D AF points. They are actually clustered in the middle:

Go to Canon USA, then go the metering section:

http://www.usa.canon.com/cusa/consumer/products/cameras/slr_cameras/eos_6d?selectedName=Features

bobn2
bobn2 Forum Pro • Posts: 53,199
Re: This is the rule

treepop wrote:

bobn2 wrote:

a) If Canon has more it definitely is important. The 61 point AF in 1D X and 5DIII is very definitely better than the 51 point AF in D4 and D800.

b) If Nikon has more it is not important. The 51 point AF in the D300s is not better than the 19 point AF in the 7D, nor is the 39 point AF in the D7000.

Therefore the AFs in the 6D and D600 are covered by rule (b). The 6D is definitely better.

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Bob

I must say. I didn't know the Cross type focus points on the D600 were all smushed in the center of the frame.

That's the way Nikon does it, and for a reason. The point is that cross sensors don't work very well towards the edge of the frame. PDAF works by directing light from opposite sides of the exit pupil onto a strip of sensors. As one moves towards the edges of the frame the light from the far edge has to be refracted through a greater and greater angle. You'll have seen that AF units do not have a lens for each focus point, generally they have four - two for each axis. So, the result is, as you move to the edges the AF stops picking up light from each side of an f/5.6 exit pupil, it picks from a laterally displaced f/5.6 'exit pupil' which will eventually fall off the actual exit pupil, and is any case subject to more distortions and aberrations. You can see this taken account in the 6D AF system - the outer points are vertical (take light top and bottom). If you miss out the cross points at the edge, the linear strip can be made more effective by using larger pixels and larger field lens. So, whether its better to have cross points towards the edge, I don't know. Obviously Nikon and Canon engineers differ on this, or maybe Canons marketing people got the better of their engineers - the deployment of vertical and horizontal on the 6D shows clearly that the canon engineers understand the issue.

That combined with the -3ev...I gata say...I would rather have the 6D.

Now if the D600 had its cross type focusing spread out, I would definitely lean towards the D600.

So good point Original Poster.

Cross points is like number of points - how do you know that an edge cross point is in practice better than an edge linear point. Answer is, you don't, you're just making an assumption on the basis of a spec.
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Bob

bobn2
bobn2 Forum Pro • Posts: 53,199
Re: This is the rule

ultimoamore wrote:

bobn2 wrote:

Therefore the AFs in the 6D and D600 are covered by rule (b). The 6D is definitely better.

What we're trying to say is that the number of points is important for action. The number of outer cross points is important for fast lens (to avoid focus&recompose).

See my comments on cross points in my previous post. Cross points don't work very well towards the edge of the frame. You can't make an assumption that outer cross points are better than linear points just because they are cross points.
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Bob

x-vision
x-vision Senior Member • Posts: 1,225
Re: This is the rule

ultimoamore wrote:

  • d600 and 6d have no outer cross points -> none is "better" for fast lenses

Well, for fast lenses, the more cross points, the better - even if clustered in the middle.

Yes, you still need to focus and recompose but more points do help with focus accuracy.

mvmv Regular Member • Posts: 204
6D and D600 AF points picture

bobn2
bobn2 Forum Pro • Posts: 53,199
Re: 6D and D600 AF points picture

mvmv wrote:

Only the relative scales are wrong.
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Bob

OP ultimoamore Regular Member • Posts: 297
Re: This is the rule
1

bobn2 wrote:

Cross points is like number of points - how do you know that an edge cross point is in practice better than an edge linear point. Answer is, you don't, you're just making an assumption on the basis of a spec.

5D mark III has edge cross points, and, reading on the forum, is TONS better than the 5D mark I/II focusing system. Linear edge points are not reliable, at least in canon world. Cross type are, even if on the edge. I don't know anything about Nikon.

Again: the biggest problem in 5D mark I/II autofocus is focus&recompose, because we bought FF cameras to use shallow DOF given by fast lenses; but we can't rely on edge, not-cross points. I really hoped that 6d had a better focusing system. Even 5 cross points would have made it...

So, my point (for my use, I don't care how many points there are: I want cross points on the edge) is based on canon autofocus systems. But I don't see the reason why a linear type on d600 should be better than a linear type on 6d. Hence the original post: d600 (on paper) doesn't help people looking to avoid the focus&recompose pattern.

Before seeing the layout, I was seriously tempted to go to d600; now I don't see the reason (for my shooting). I actually like (on paper) the focusing system of 6d more (given the -3 ev thing)

(small edit: I'm not trying to say that 6d is a better camera overall. Far from it. I'm just discussing the autofocus systems in the 2 cameras)

mvmv Regular Member • Posts: 204
6D and D600 AF points picture, corrected?

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