6D AF and Focal Plane issues by recomposing

[Loswr]

Nikon's 3D tracking = Canon's AI Servo.

Oh, thanks. Thats exactly what I wanted to know. Now, does it work properly on the 6D?
I am just afraid, only the 5D MIII (not to mention the 1´s) can perform well in this discipline and €2800 are out of my reach.

Probably ok on the 6D, but definitely better on the 5DIII.

 

[dr croubie]

+1 for the Tripod, Live-view, 5x or 10x mag, and getting it right the first time.
Set up the tripod, frame, lock the head.
Live-view, magnify in, set your focus.
*ZOOM OUT TO 1x MAG* before you set your light readings (at least on my 7D if you take a light reading at 5x or 10x mag, it might not be accurate for the whole frame).

Not only does focus/recompose not work at f/1.2, or anywhere that DOF is less than a few cm (even 300mm f/4 is wafer thin on FF), but even regular focus is enough of a nightmare in one-shot mode.
I've had scenarios, even with something not-completely-wafer-thin like an EF 85mm f/1.8, in one-shot AF mode where the subject moved 1cm, or I swayed in the wind, or whatever, and it ended up OOF.

The only way I ever shoot under f/2.8 (unless it's on a UWA lens) is with AI Servo, or tripod, liveview, and 5x mag.

 

[beansauce]

If my depth of field is that tight and the possibility of focus shift is evident when using this method, I'll quickly turn on live view, zoom in a bit, and achieve focus MANUALLY. Practice a bit, and this gets fast.

 

[J.R.]

+1 for the Tripod, Live-view, 5x or 10x mag, and getting it right the first time.
Set up the tripod, frame, lock the head.
Live-view, magnify in, set your focus.
*ZOOM OUT TO 1x MAG* before you set your light readings (at least on my 7D if you take a light reading at 5x or 10x mag, it might not be accurate for the whole frame).

Not only does focus/recompose not work at f/1.2, or anywhere that DOF is less than a few cm (even 300mm f/4 is wafer thin on FF), but even regular focus is enough of a nightmare in one-shot mode.
I've had scenarios, even with something not-completely-wafer-thin like an EF 85mm f/1.8, in one-shot AF mode where the subject moved 1cm, or I swayed in the wind, or whatever, and it ended up OOF.

The only way I ever shoot under f/2.8 (unless it's on a UWA lens) is with AI Servo, or tripod, liveview, and 5x mag.

+100 ... pretty much nailed it there

 

[Frage]

If my depth of field is that tight and the possibility of focus shift is evident when using this method, I'll quickly turn on live view, zoom in a bit, and achieve focus MANUALLY. Practice a bit, and this gets fast.

I was thinking of using MagicLantern´s Focus Peak, but not in FF camera (I would buy). In a FF camera I want to use the VF.

 

[Ryan708]

I wonder if some of the lenses that have strong "field curvature" would cancel out the focus-recompose teqnique. if your focal plane was shaped like a " ( " for example, tilting the camera would all be on same focal plane. Sorry If i lost you, im sure a few people will see my point.

 

[dr croubie]

I wonder if some of the lenses that have strong "field curvature" would cancel out the focus-recompose teqnique. if your focal plane was shaped like a " ( " for example, tilting the camera would all be on same focal plane. Sorry If i lost you, im sure a few people will see my point.

Possibly, but with a caveat.
The reason Focus+recompose doesn't work for a flat plane is because the distances change *if you rotate the camera around the nodal point of the lens*.
If, however, you rotate around your neck (which is what I would probably do), it is still possible (although *highly* unlikely), that you manage to still catch the focus where you want.

With a curved plane of focus (like on a fisheye, which afaik is a curved plane of focus bending around the lens), yes, there is the possibility to rotate around the nodal point and/or around your neck and keep the focus on the intended subject *if you know exactly how the plane is curved and can adjust yourself properly*.
Again, you've probably got just as much chance of catching the focus as with a flat plane.

But, there's one more problem. Lenses with curved planes of focus can also bend the other way, and as far as I know that's a lot more common. ie, focal point is 5m away in the centre of the image, and focus is at infinity on the edges. See the nice graphic here. Focus on something in the centre, turn your head a bit, and suddenly they're even more oof than if you'd used a true flat-planar lens.

So yes, it is technically possible to focus/recompose with all of a flat plane, curved plane towards you, and a curved plane away from you. But unless you know the *exact* distances and *exact* way and shape that the plane of focus is curved, then any photos in focus using this technique will be purely coincidental (and a lucky chance).

 

[ishdakuteb]

http://www.visual-vacations.com/Photography/focus-recompose_sucks.htm

http://digital-photography-school.com/the-problem-with-the-focus-recompose-method

Great links, thanks!

Since recomposig sucks (visual-vacations.com dixit), I was just wondering how it all happens on a 6D.

well... i certainly can perform either way (re-compose or select one of those focus point) if you can lend me a 6d. i bet that canon 6d is much much better than a camera that i am using everyday for experiment purpose which is canon 30d (note: i am using select focus point on this one).

for ai servo, if i still remember correctly, canon suggests to track your subject starting from center focus point for better result.

one of a renown photographer who prefers to use re-compose technique is bambi cantrell. it is just the matter of technique that you have to train yourself when preferring to use it that way.