Is recomposing ideal rather than changing focus point?

Question

As a beginner in photography I’ve stumbled across several videos stating that the center point is the sharpest and most accurate point as apposed to the others.

I’ve seen many photographers take very quick shots and they always get the subject very sharp regardless of the location of the subject, sometimes I never see them change focus point and leaves me to wonder are they really recomposing the frame while keeping the camera on the center focus point?

I ask because during photoshoots I feel rushed when switching focus point just to get the subject where I want them in my frame while still being sharp. Aren’t you prone to unsharp images when recomposing?

Answer 1

As a beginner in photography I’ve stumbled across several videos stating that the center point is the sharpest and most accurate point as apposed to the others.

Not necessarily. Cross-Type autofocus points are better at their job and each model camera has more or less of these. A consumer grade camera may only have 1 cross-type in the center, but as you go up the food chain, you get more and more cross-type points available to you.

I’ve seen many photographers take very quick shots and they always get the subject very sharp regardless of the location of the subject, sometimes I never see them change focus point and leaves me to wonder are they really recomposing the frame while keeping the camera on the center focus point?

Maybe so, maybe not. I know that I've got the little joystick-like toggle button on the back of my 5Dmk2 configured to select the AF point at any time - so switching it is muscle memory. I use the custom function to assign autofocus on/off to the other button that's right there - so my thumb is already doing a lot of action back there.

But, let's say they are recomposing. If they're tilting the camera while recomposing, but also using a small enough aperture to compensate (widening the DoF), then they can essentially get away with it.

The other way to to recompose is to shift the camera instead of tilting it. For example, center-focus on the face and then keep the camera at the same angle and bend your knees to realign the shot. The distance to the focal plane remains the same - and it's possible these other photographers are recomposing with this technique as opposed to the tilt method.

I ask because during photoshoots I feel rushed when switching focus point just to get the subject where I want them in my frame while still being sharp. Aren’t you prone to unsharp images when recomposing?

Feeling rushed will go away as you get more experience and operating your camera becomes second nature. Recomposing using a tilt does change where the focal plane is, and yes, you risk the focus being in the wrong spot. Aperture can CYA here. But, if shooting wide open, and if recomposing, make sure you don't tilt the camera but shift it instead and you should be golden.

Answer 2

Neither method is "ideal" for all situations. Sometimes one will do better, at other times the other will.

There are several variables that affect when it is better to use the center AF point and then recompose and when it is better to use the nearest AF point to your subject.

• Shooting conditions. In brighter light AF points function better than in low light. Peripheral points tend to do well enough in good light. The center AF point is usually better in low light. Part of that is just the laws of physics and how PDAF systems work.
• AF system design. Many times the center AF points are cross type or even dual cross type AF "points" that give them better performance in low light. If an AF "point" over your subject is only sensitive to vertical contrast and your subject's contrast is mostly horizontal, using another AF point nearby that is sensitive to horizontal contrast might work better.
• The shooter's technique. If doing focusing and recomposing, rotating the camera around the optical center of the lens works a lot better than rotating around the center of the photographers body, which is most people's natural tendency.

All AF "points" are sensitive along a straight line. They detect contrast lines that are oriented 90° to the direction of the line on the AF sensor array. Most "single" AF points are either sensitive to horizontal contrast lines or to vertical contrast lines. A few AF systems have single diagonal lines that make them equally sensitive to horizontal or vertical contrast lines, but they are not as sensitive to either as a vertical line would be to horizontal contrast, or vice versa. "Cross-type" AF points are simply two lines superimposed over each other at a 90° angle. "Dual cross-type" AF points are two cross-type points superimposed over each other with one at a 45° diagonal to the other.

_{An illustration that demonstrates the AF system of the Canon EOS 7D Mark II (left) and the Canon EOS 1D X and EOS 5D Mark III (right).}

Each AF point uses a pair of lines oriented to detect the light coming from opposite edges of the camera's lens. The distance from one side of the lens to the other is determined by the lens' maximum aperture, since AF is done with the lens' aperture wide open. How far apart the pairs are determines their "sensitivity". Pairs that are closer together can function with lenses with narrower maximum apertures. Pairs that are further apart can be more accurate and more sensitive in lower light, but they don't work at all with lenses too narrow for them. Most f/2.8 AF points are the diagonal cross points in the center.

Answer 3

Disclaimer: This is the opinion of a semi-professional photographer - my professional work mostly consists of shots of groups of people, parties, and speeches, so usually, I do not have a lot of time between shots. I also do portraits, which are quite relaxing by comparison. Perhaps also important: I use a 5D Mark III, which offers a pretty good autofocus experience.

To me, it depends.

• I usually switch the AF point to the one that is closest to the (main) subject in my composition - with increasing routine, this can be done in the matter of a second (when changing the composition).
• For small variations of the same composition (just a little higher/lower/...), which vary by less than 2 AF fields, I usually stick to recomposing.
• If something unforeseen happens (maker forbid), trying to get the shot is the first priority, so I recompose.
• With other cameras that offer less AF points and perhaps far less AF area, I usually select the field closest to the subject and recompose.

These things change when it gets dark and both the subject and I stand (almost) still: Then, I usually stick to the center AF point (area), as it usually offers better low-light performance, and recompose.

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As to accuracy: I never had a problem with one of the more peripheral AF points. They could be a problem with lenses that have a lot of distortion (say: a fisheye), but usually, they are far more exact than I am when recomposing the shot.

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One last point that comes into mind is metering. If you work with one of the (semi-)automatic modes (P, Tv, Av, M with ISO set to Auto), it could be that due to the lighting conditions, you need to recompose.

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I think all of this really depends both on your technique (~80%) and your gear (~20%).

I would say that no matter whether you own a 300D or a 1D X Mark II, you should know both techniques by heart (and ideally, you should also train to focus manually) so you can switch between them dynamically. Some time, changing AF fields will be sufficient. Another time, recomposing might be needed. There is no excuse for not knowing them - e.g. if your camera's peripheral fields do not deliver sufficient results, then there will be no excuse to not switch techniques.

Answer 4

I'll start with your ending question: yes, I find myself having to delete quite a few out of focus shots while I wait for my AF to find my subject.

Backing it up - I certainly move around my subject (and consequentially re-frame) to keep my center point on the subject, and sometimes I'll take an exposure then and there. Lately, though I've found that I can briefly half-press the shutter so that my AF focuses on the center point before I adjust the frame and fully press the shutter to take the shot. So long as the subject didn't move, and I didn't either aside from my small frame adjustments, the shot comes out clean more often than not.

As a beginner photographer, I recommend you try to familiarize yourself with manual focus, as there will be certain situations where your AF will have a hard time focusing, and it's better to be comfortable with it now before you miss a potentially great shot.

Have fun with the new hobby! @torkupine