7d single point vs spot autofocus for action?

Just trying to clear this up. I seem to remember reading that the 7d when in spot af mode will focus slower than in single point. Is this true or are they both equal in terms of speed?

I tend to leave the 7d on spot for almost everything. I mostly do birding and like to be prepared in case they take flight.

What does everyone else use?

Thanks,

Travis

For Birds, in fact all the time I use Centre point with assist, also slow down the refocus response. Seems to work well for me.

Spot focusing may take longer to focus and may be less accurate than single point. Because spot looks at a smaller portion of the image the chance of it looking at an area with insufficient contrast for the AF algorithm to work is higher with spot than with single point.

Look at Ken's cool image above. Spot focusing may only have covered the bit of head behind the eye of the middle bird, where there's not a lot of contrast. Single point, when pointed at the same place, will also cover the top and/or bottom of the head - where there's loads of contrast.

Like Ken I use single point plus expansion. Unlike Ken I don't always use the centre point, espcially for BiFs where I'll normally pick one of the points to the left/right. Otherwise you're forced to centre the bird's head which can have adverse effects on composition.

Spot AF is great for modeling shots, static scenes or portraits (where you want to concentrate your focal point), and birds in branches, etc. I would not use it for fast moving targets, and even Canon warns of the implications of that when using spot AF in their white papers.

Like others, in those situations I use single point or SP with expansion.

TeamSpeed wrote in post #15442829
Spot AF is great for modeling shots, static scenes or portraits (where you want to concentrate your focal point), and birds in branches, etc. I would not use it for fast moving targets, and even Canon warns of the implications of that when using spot AF in their white papers.

Like others, in those situations I use single point or SP with expansion.

This is how I use it for BIF and fast moving objects. I tend to the SP with expansion. This worked real well for me the first time I tried BIF since it was my first attempt at panning.

I us SP with expansion and spot for almost all else.

Spot can be much more accurate if your subject is in clutter or very small in the frame.

I guess spot might be slower or work less well in low light in theory but I have not noticed a difference between spot and SP in most situtations.

artyman wrote in post #15442557
For Birds, in fact all the time I use Centre point with assist, also slow down the refocus response. Seems to work well for me.

This is what I do also.
Slow the AF response so it doesnt focus on the background if you slip off the bird.
Use AF expansion (its the single point with 4 points around it) for action stuff

I use spot for small birds and static objects.
While Frank is right, it can lead to issues with low contrast I have found that the single full size point can lead to issues because the actual AF area is larger than the point on the screen. So if you hit the head of the bird it may pick up on a branch behind the head and soften your shot significantly.

Take 2 shots if you can. 1 in spot and one in center!

IIRC the manual recommends to not use spot AF in AI Servo continuous burst.

Like others have posted, I use it for precision focusing when the subject is surrounded by clutter.

Thanks everyone. I'll try single point and single point with expansion and see how it goes.

On my 60d I had a tough time tracking 8 year old daughter in soccer. Longed for single point with expansion.

Spot Focus reduces the size of the AF point, making it more precise, more accurate, but at the cost of some speed when tracking in AI Servo. It's primarily for situations where you are shooting through blades of grass or tree branches... also useful for really exacting focus for shallow depth of field portraits, macro. Some folks have success with it shooting moving subjects in AI Servo, but I suspect most of the time you'd get a slightly higher keeper rate reverting back to Single Point focus mode. Spot Focus works very well with One Shot. The reason it's slower at tracking... or might miss entirely... is exactly what Frank mentions... less of the scene is being evaluated, so with Spot Focus there's greater risk that there won't be contrast or detail to lock onto.

In Spot Focus mode, the AF point size is reduced in size so that it's within the normal AF point "box" seen in the viewfinder. It's pretty close to the size of the secondary box only displayed in the Spot mode.

As Jeremy noted, the Single Point AF point is actually a little larger than the box indicated in the viewfinder. In partucular it seems to go beyond the top of the box, primarily (when using the camera in horizontal or landscape orientation). The sides and bottom seem fairly accurate.

If subjects are a bit erratic in their movements, try Expansion Points. With this, you select a single starting point manually, and the points around it will kick in if you don't keep the selected point rignt on the subject. Just be aware that if you select a point at any of the edges of the AF point array, it will be limited to expanding only to the points on the three remaining sides.

Zone Focus looks like Expansion, but it's not. It activates a group of points equally. Any one of them can be the starting point and/or take over from it's neighbor if needed. In a sense, Zone Focus is sort of a scaled down version of All Points/Auto Selection. These modes work best when there's little or nothing behind or in front of the subject, that might distract the AF system. Think of a flock of birds flying past you, against a fairly plain sky (some distant clouds usually aren't a problem).

AI Servo Tracking Sensitivity (C.Fn III - 1) can be set on 7D and some of the other cameras. You might try slowing this down initially (-1 or -2). It's actually controlling how quickly the AF will jump to another target, should something come between you and your subject... or how quickly AF will jump to a background if you fail to keep the active AF point on the subject. It doesn't actually change AI Servo speed of acquisition or ability to track at all. Later, as you are more skilled at tracking subjects, you probably would be able to turn this setting back up. I think a faster setting helps a bit if subjects change directions a lot.

On 7D (and probably some others), you also might want to set AI Servo 1st/2nd Image Priority different than the default. This allows you to change how the camera prioritizes AF accuracy vs shutter release for the first shot, and AF accuracy vs tracking accuracy on the 2nd and all subsequent shots in a series. I leave it set on the default 0: AF Priority/Tracking Priority. This tells the camera to emphasize focus accuracy all the time when in AI Servo, even if it delays shutter release slightly or slows down the frame rate during a series of shots (the item before the / is applied to the first image, the selection after the / is applied to the 2nd and subsequent series shots). I just figure I'd rather have in focus photos as much as possible, rather than lots of shots at the highest possible frame rate. Out of focus shots do me little or no good.

I use Single Point about 75-80% of the time. I probably use Spot Focus second most often, maybe 10-12% of the time. I'll use Expansion mode 5 to 7% of the time. The remainder, probably under 5% of the time... i.e., rarely... I use Zone Focus mode. I virtually never use All Points/Auto Selection.

60D is just like the 50D and 40D before it... Best to select a Single Point manually and work to keep it on your target. Because they are all dual-axis, all nine work pretty well. However, the center point is still a bit better and often is the best choice. Set the camera to AI Servo (not AI Focus)... Try using Back Button Focusing. (BBF works very well on 7D, too.)

amfoto1 wrote in post #15445422
Spot Focus reduces the size ...ly and work to keep it on your target. Because they are all dual-axis, all nine work pretty well. However, the center point is still a bit better and often is the best choice. Set the camera to AI Servo (not AI Focus)... Try using Back Button Focusing. (BBF works very well on 7D, too.)

Wow thanks for the informative post. I'll have to read through this a couple more times.

Very well said amfoto1. The focusing features of the 7D can be complex but it is designed to fit many different types of shooting.