Focus Point Selection... and focus buttons... what do you use?

[VirtualRain]

I have a 9-point AF system in my T1i with the center point having added sensitivity with f2.8 lenses or better (eg. my 17-55). Wanting to get the best capture rate, I've been using the center AF point almost exclusively... using the old trick of focusing and then reframing to complete the shot. I shoot mostly people and places... not a lot of sports.

The one time I've used it for sports, I still kept it on center AF point, but switched to AI servo mode. This worked fine.

Am I wasting the capabilities of my camera's 9 AF points and it's ability to auto-select or am I wise to exclusively rely on my center point only? Should I just trust the camera more and use auto AF selection? I certainly don't see the point of manually selecting the AF point for each shot... it's a LOT easier to just keep it set on center AF point and reframe the shot than to fiddle around with AF point selection... do other people change the AF point routinely?

In my old Elan IIe 35mm camera, I had 3 focus selection points (left, right, center) and the camera could detect which one my eye was looking at and select that one for focus... This was back in 1996. Why that technology never made it to DSLR's is a mystery to me. Maybe I'm becoming a ludite but that seemed like a superior system to the 9AF points I have now and the buttons and knobs I need to adjust to pick one. Hence I'm stuck in the 80's using a single AF point and reframing.

I'm drawn to the wicked fancy AF system in the 7D, but can't imagine how I would use it. Certainly setting it manually to center AF point almost exclusively and reframing is an absolute waste of this camera's focus potential. For those of you who have a 7D or something equally as sophisticated... how do you routinely use your focus points?

What about back button focus? That's an option... but I don't know why I'd want to do that.

Some best practices in using the focus systems in these camera's would be much appreciated. I'd like to get the most out of my camera while still getting the best rate of keeper shots and at the same time, start to understand how a more sophisticated focus system like the one on the 7D (my likely migration path) would benefit me.

 

[firestarter]

I use only the central focus point on all my Canon cameras, coupled with moving focussing to the back button.

I like to shoot fairly close-up portraiture with low DOF, so I need that sort of accuracy to make sure I get eyes in focus. I wouldn't trust the camera to select its own focus point, and messing with a joystick or whatever to select a different focus point for each composition just wouldn't work.

I think the rear focus button works well in this sort of setup, as it clearly separates the act of focussing from composition and exposure. I don't like the idea that taking my finger off the shutter would force a refocus when I re-applied it.

 

[Kebabselector]

it clearly separates the act of focussing from composition and exposure. I don't like the idea that taking my finger off the shutter would force a refocus when I re-applied it.

The exact reason I use rear button focusing on my 5D. On the subject of using rear button, I tried the 7D's rear on button and found it wasn't as natural as the '*' button. Fortunately if can be changed in the Custom Settings on the 7D, which is handy as I may get one soon.

 

[jampat]

If the light is bad, I use the center focus point as it's my only cross sensor and has a better chance of locking on. If the light is good, I use the top right point often as the move to recompose is much smaller than coming from the centre spot.

On servo I almost always use one of the points off center as you can't recompose.

I don't normally move the focus point around during a shoot, I just pick the point I want to use at the beginning and recompose if required.

 

[VirtualRain]

Thanks guys. I'm finding this forum frustrating... 100 views as of this post on a subject that everyone should be able to comment on, and only 3 replies.

Anyway, I found this informative piece on the potential issues related tousing the center focus point and recomposing the shot...

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

Here's the jist of it...

In this example, the correct distance setting is 6.456 feet, represented by the horizontal green line. If the camera is reoriented so that the center AF sensor focuses on the correct spot between the subject's eyes, focus distance will be set at 6.679 feet, represented by the diagonal red line. This will result in the focus distance being set 2.676 inches farther out than the correct distance, which means that when the camera is tilted back to achieve correct framing, the center of focus will be along the vertical red line instead of the vertical green line where it belongs. If the camera was tilted up by tilting the tripod head back, the error would be increased another few inches, since the camera would be moving away from the subject an additional few inches as it was tilting up. The setup pictured above would approximately double the focus error amount previously mentioned. Your mileage will vary, depending on the configuration of your tripod head.

Good stuff. From now on, I will definitely try to avoid this technique with shallow-depth of field shots.

 

[toxic]

the center point is always the most accurate (or has the potential to be) since it receives the most light. the outer points are usable, but the reliability suffers, especially with single-line points on the 5D, 20/30D, and consumer (Rebel) cameras. they are fine with stationary subjects but aren't generally used in fast-moving action. you also have to pay attention to the contrast lines and make sure the AF line is perpendicular to the contrast line.

generally, it's best to use the center AF point, but as you found out, at close distances that isn't the best option. so for things like portraiture or macro, you either use the nearest AF point or focus manually.

and Canon decided not to continue with eye-control focus probably because a lot of users thought it was too unreliable and not worth the extra cost.

 

[someoldguy]

Almost always use the center point on my 5D , guess its a throwback to when I was a kid using manual focus SLR's , but it works for me . Too many choices complicates things and I don't usually like the ones my camera makes for me re: focusing points.

 

[jackerin]

Thanks guys. I'm finding this forum frustrating... 100 views as of this post on a subject that everyone should be able to comment on, and only 3 replies.

Yes, but why would they if their opinion is brought forward by another poster? If you want to make a poll then I think there is an option for that...

Always use focus-recompose myself. When using my 50mm 1.8 I've noted far more instances of it just completely missing focus unless it's in good light. Solution: manual focus + live view. (Mark 1 with real focus ring, yo.)

 

[AlaskaMoose]

I have a 9-point AF system in my T1i with the center point having added sensitivity with f2.8 lenses or better (eg. my 17-55). Wanting to get the best capture rate, I've been using the center AF point almost exclusively... using the old trick of focusing and then reframing to complete the shot. I shoot mostly people and places... not a lot of sports.

The one time I've used it for sports, I still kept it on center AF point, but switched to AI servo mode. This worked fine.

Am I wasting the capabilities of my camera's 9 AF points and it's ability to auto-select or am I wise to exclusively rely on my center point only? Should I just trust the camera more and use auto AF selection? I certainly don't see the point of manually selecting the AF point for each shot... it's a LOT easier to just keep it set on center AF point and reframe the shot than to fiddle around with AF point selection... do other people change the AF point routinely?

In my old Elan IIe 35mm camera, I had 3 focus selection points (left, right, center) and the camera could detect which one my eye was looking at and select that one for focus... This was back in 1996. Why that technology never made it to DSLR's is a mystery to me. Maybe I'm becoming a ludite but that seemed like a superior system to the 9AF points I have now and the buttons and knobs I need to adjust to pick one. Hence I'm stuck in the 80's using a single AF point and reframing.

I'm drawn to the wicked fancy AF system in the 7D, but can't imagine how I would use it. Certainly setting it manually to center AF point almost exclusively and reframing is an absolute waste of this camera's focus potential. For those of you who have a 7D or something equally as sophisticated... how do you routinely use your focus points?

What about back button focus? That's an option... but I don't know why I'd want to do that.

Some best practices in using the focus systems in these camera's would be much appreciated. I'd like to get the most out of my camera while still getting the best rate of keeper shots and at the same time, start to understand how a more sophisticated focus system like the one on the 7D (my likely migration path) would benefit me.

I use the center point to focus on the eyes of a person, pet, etc., macro photography, and for action shots with AI-Servo active. But seldom refocus the lens manually. I only focus manually on macro photography.

For wide landscapes and cityscapes, then I use all the focus points, but close my Tokina 12-24mm lens aperture to a minimum of f/11 or a maximum of f/22 (depending on the subject).

But there are times when I use another focus point other than center. For example, depending on lens aperture and DOF, I may decided to use whichever focus point falls on an area other than the eyes I want in focus, since I already know that the eyes will be in focus, too.

 

[VirtualRain]

Any 7D owners in the house? I'm curious to hear what your focus point strategy is.

From reading this thread, you'd assume that there's little need for more than one focus point.

 

[jampat]

Any 7D owners in the house? I'm curious to hear what your focus point strategy is.

From reading this thread, you'd assume that there's little need for more than one focus point.

The way Nikon implements it (with the focus point tracking the object) is awesome and requires all the points. With Canon, unless you are shooting servo, in most cases you could get away with one point (although some exceptions have already been pointed out above).

 

[Patriks7]

So far I've only been using the center point (have had no need in using anything else, at least hadn't had a situation where it would have been advantageous). But I never understood how this thing works, with changing the focus button. I have it set on my normal shutter button, but haven't figured out a way to change it (I have a 40D btw). What are the advantages in changing it anyway?

 

[Kebabselector]

Forgot to mention about my focus points, or should I say point. Yes its the central for most shots. Maybe on Macro I might select a different one, but it's not very often.

On film (Eos 50E - think it might have been the Elan in the US) I used all 3 focus points, but that's because it had Eye Controlled focus.