October 23, 2017, 02:22:32 AM

Author Topic: Sports shooters: single or expanded AF points?  (Read 5530 times)

Ian_of_glos

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Re: Sports shooters: single or expanded AF points?
« Reply #30 on: September 24, 2017, 01:06:57 PM »
Some pictures from yesterday's match. The results surprised me.
To start with I used single point AF, but after 15 minutes I was missing too many shots so I switched to expanded AF point.
These are a couple of the pictures taken using Single point AF. I was using AI Servo and high speed continuous so the photos were taken less than a second apart.
What surprised me is that in both cases the AF point was on the green player's leg. I was expecting the AF point to be on the advertising behind him in the out of focus shot.

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Re: Sports shooters: single or expanded AF points?
« Reply #30 on: September 24, 2017, 01:06:57 PM »

Ian_of_glos

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Re: Sports shooters: single or expanded AF points?
« Reply #31 on: September 24, 2017, 01:18:09 PM »
Here is another example where I used Single Point AF. This time the focus point is on the blue player's hand which again surprised me. I was expecting to find that the AF point was on the advertising behind the players as this is clearly what is in focus. Is it possible that DPP is not displaying the AF point correctly?
Again I have included a shot that was taken less than a second later and this time the AF point has found the blue player's shorts, so the players are in focus

Ian_of_glos

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Re: Sports shooters: single or expanded AF points?
« Reply #32 on: September 24, 2017, 01:31:09 PM »
After 15 minutes I switched to AF point expansion because too many shots were out of focus when I used single point AF. AF point expansion was a lot better - only one shot was out of focus even though I used this mode for over 25 minutes.
This is the only shot that was out of focus when I was using AF point expansion and this time the AF point is clearly on the advertising. I am willing to accept that I was not quick enough when I tried to place the AF point over the green player who is about to catch the ball.
Before this experiment I was expecting AF point expansion to be just as bad as single point AF - because if the centre AF point was positioned over the advertising then I would expect it to find enough contrast and therefore not use any of the helper AF points. However, in practice it did a cracking job and this was the only shot I missed in 25 minutes of play.

Jack Douglas

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Re: Sports shooters: single or expanded AF points?
« Reply #33 on: September 24, 2017, 01:40:09 PM »
Here is another example where I used Single Point AF. This time the focus point is on the blue player's hand which again surprised me. I was expecting to find that the AF point was on the advertising behind the players as this is clearly what is in focus. Is it possible that DPP is not displaying the AF point correctly?
Again I have included a shot that was taken less than a second later and this time the AF point has found the blue player's shorts, so the players are in focus

This is very much appreciated - taking the time to shoot and then post! 

I'm grappling with similar issues with BIF or almost flight.  No, DPP is not wrong, it's the AF system being too slow to adjust.  I have countless examples of this and even sent some to Canon.  Keep in mind that the AF capability diminishes as you go away from one-shot dead center and is worst at the extreme edges even with the best cameras.

Jack
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Ian_of_glos

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Re: Sports shooters: single or expanded AF points?
« Reply #34 on: September 24, 2017, 01:59:27 PM »
During the second half of the match I only used zone AF. This is the mode I normally use so I was expecting a higher success rate, but I was surprised to find that there were more out of focus shots than with AF point expansion. There was a total of 6 out of focus shots when I was using zone AF, and I have included some examples below.
In the first example no part of the zone is positioned over a player - clearly my fault and nothing to do with the camera. I had been focussing on the tackle on the right hand side of the picture when the player offloaded the ball, and I ended up mid way between the player being tackled and the player he was passing to.
In the second example - none of the AF points are illuminated - so I have no idea what happened. A split second later the AF seemed to catch up and so the next shot is in focus.
Finally, in the third example again I am confused. The blue player's arm is clearly within the AF zone but the camera has chosen to focus on the spectators behind him. I would have expected it to focus on the player as he is within  the AF zone and closer to the camera. Can anyone suggest a reason why it has missed focus in this case?

awair

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Re: Sports shooters: single or expanded AF points?
« Reply #35 on: September 24, 2017, 02:01:27 PM »
Hi Ian,

Thanks for posting these. I had similar results with my 7D2, which went back to Canon twice with no improvement - on the third occasion I told them to keep it.

While I've had the occasional poor result with the 1DX, for the most part any errors have been mine, although I did have a couple (like your Single Point AF 2.jpg), where the focus point clearly identifies a point that is most definitely not focussed.

As Jack says, "it's the AF system being too slow": which AF case were you using, and have you made any customisations? I've used Case 2, 3 & 6 for this kind of scenario, with mixed results - I tend to fall back to Case 2.
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awair

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Re: Sports shooters: single or expanded AF points?
« Reply #36 on: September 24, 2017, 02:07:41 PM »
With Case 2, it's my responsibility to keep tracking the subject & the camera takes care of brief interruptions. Errors normally occur when I can't maintain the subject accurately enough, due to lack of anticipation, excess distance or just too many people in the way.

With Case 3, the camera locks on quicker (more responsive), but with Single Point if you fail to track you will get a quick shift to the background!

Case 6 is me giving up (on over-thinking) and wishing for an improvement!

I feel like I have more control and responsibility with Case 2,  but still not entirely sure that I have really got the hang of it.
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Re: Sports shooters: single or expanded AF points?
« Reply #36 on: September 24, 2017, 02:07:41 PM »

Ian_of_glos

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Re: Sports shooters: single or expanded AF points?
« Reply #37 on: September 24, 2017, 02:08:19 PM »
Here is another example where I used Single Point AF. This time the focus point is on the blue player's hand which again surprised me. I was expecting to find that the AF point was on the advertising behind the players as this is clearly what is in focus. Is it possible that DPP is not displaying the AF point correctly?
Again I have included a shot that was taken less than a second later and this time the AF point has found the blue player's shorts, so the players are in focus

This is very much appreciated - taking the time to shoot and then post! 

I'm grappling with similar issues with BIF or almost flight.  No, DPP is not wrong, it's the AF system being too slow to adjust.  I have countless examples of this and even sent some to Canon.  Keep in mind that the AF capability diminishes as you go away from one-shot dead center and is worst at the extreme edges even with the best cameras.

Jack
Jack - thank you for your feedback.
So do you think that if I set AI Servo First Image Priority to Focus Priority then I would have a better success rate? At the moment it is set to Equal Priority because I am worried about there being too much of a delay between pressing the shutter release and the camera taking the first picture in the series. It is only a 5D mark 4 and not really a sports camera, so I understand that I have to make some allowances for that.

Ian_of_glos

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Re: Sports shooters: single or expanded AF points?
« Reply #38 on: September 24, 2017, 02:55:57 PM »
Hi Ian,

Thanks for posting these. I had similar results with my 7D2, which went back to Canon twice with no improvement - on the third occasion I told them to keep it.

While I've had the occasional poor result with the 1DX, for the most part any errors have been mine, although I did have a couple (like your Single Point AF 2.jpg), where the focus point clearly identifies a point that is most definitely not focussed.

As Jack says, "it's the AF system being too slow": which AF case were you using, and have you made any customisations? I've used Case 2, 3 & 6 for this kind of scenario, with mixed results - I tend to fall back to Case 2.
Thank you for your comments.
I am using Case 2 unaltered. This is the best mode for rugby because people frequently run in front of the camera and I don't want the camera to focus on them. Most of the time the camera ignores them and remains focussed on the action.
Rugby players tend to move in one direction and their movements is not really erratic so I don't think cases 5 or 6 would offer any improvement.
When players are running towards the camera they maintain a fairly constant speed so I don't think case 4 is needed either.

Jack Douglas

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Re: Sports shooters: single or expanded AF points?
« Reply #39 on: September 24, 2017, 05:58:39 PM »
Quote
Jack - thank you for your feedback.
So do you think that if I set AI Servo First Image Priority to Focus Priority then I would have a better success rate? At the moment it is set to Equal Priority because I am worried about there being too much of a delay between pressing the shutter release and the camera taking the first picture in the series. It is only a 5D mark 4 and not really a sports camera, so I understand that I have to make some allowances for that.

Unfortunately, I'm not even close to being an expert on this but I think the 1st 2nd priority issue may play into the overall performance of the AF in this case.  I believe it was Grant Atkinson who delved into that topic and today with a bad headache I can't quite recall - maybe someone can help - I believe he had a series of videos and suggested not using cases at all rather just setting the 3 parameters that constitute the cases, via your personal menu.  Seems only one parameter is of greatest importance.

What I can say with authority is that the AF system is not as fast as it needs to be to insure that when a AF point is over a subject, that subject is always going to be in focus. 

That's a completely unrealistic expectation especially when using less sensitive points and lenses that may not be the fastest in their drive characteristic.  If you think of it, a brain has to analyze some smudgy area and decide what part of it should be in focus taking into account the movement of the camera and the movement of the smudge and then snap the lens into focus at that distance, which probably by now has changed slightly, and also determine when to let the shutter go.  Ooooh, quite a task!

Jack
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stevelee

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Re: Sports shooters: single or expanded AF points?
« Reply #40 on: September 24, 2017, 06:52:33 PM »
Would facial recognition focusing make sense for some of these situations or is that mode incompatible with some other setting you need?

Ian_of_glos

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Re: Sports shooters: single or expanded AF points?
« Reply #41 on: September 25, 2017, 03:22:26 AM »
Quote
Jack - thank you for your feedback.
So do you think that if I set AI Servo First Image Priority to Focus Priority then I would have a better success rate? At the moment it is set to Equal Priority because I am worried about there being too much of a delay between pressing the shutter release and the camera taking the first picture in the series. It is only a 5D mark 4 and not really a sports camera, so I understand that I have to make some allowances for that.

Unfortunately, I'm not even close to being an expert on this but I think the 1st 2nd priority issue may play into the overall performance of the AF in this case.  I believe it was Grant Atkinson who delved into that topic and today with a bad headache I can't quite recall - maybe someone can help - I believe he had a series of videos and suggested not using cases at all rather just setting the 3 parameters that constitute the cases, via your personal menu.  Seems only one parameter is of greatest importance.

What I can say with authority is that the AF system is not as fast as it needs to be to insure that when a AF point is over a subject, that subject is always going to be in focus. 

That's a completely unrealistic expectation especially when using less sensitive points and lenses that may not be the fastest in their drive characteristic.  If you think of it, a brain has to analyze some smudgy area and decide what part of it should be in focus taking into account the movement of the camera and the movement of the smudge and then snap the lens into focus at that distance, which probably by now has changed slightly, and also determine when to let the shutter go.  Ooooh, quite a task!

Jack

Thank you for the tips.
The lens used in all my shots was a Canon 100-400 F4.5-5.6L ii. This lens is great for sports and I find it always focusses very quickly - in the examples above you will see that it focussed on the background and then back onto the player without noticeably reducing the number of shots per second.
Next time I will try using focus priority to see if that makes a difference. Normally I discard all my out of focus shots so I would rather put up with a slight delay than capture an image that I am unable to use. Focus priority might be exactly what I need.

Ian_of_glos

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Re: Sports shooters: single or expanded AF points?
« Reply #42 on: September 25, 2017, 03:32:56 AM »
Would facial recognition focusing make sense for some of these situations or is that mode incompatible with some other setting you need?
Well I never use live view for sports. Live view might be fine for landscapes where you have plenty of time to compose the shot, but for sports you really need to use the viewfinder. Also the phase detect AF points are designed to focus very quickly, which is what you need for fast action.
As you will have seen from the examples I posted yesterday, you don't often focus on a player's face. More commonly the AF system will pick up the ball or the good contrast between a player's shirt and his arm. Quite often the AF point settles on the back of a player so in this situation facial recognition would be of no use.

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Re: Sports shooters: single or expanded AF points?
« Reply #42 on: September 25, 2017, 03:32:56 AM »

Viggo

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Re: Sports shooters: single or expanded AF points?
« Reply #43 on: September 25, 2017, 04:22:12 AM »
Would facial recognition focusing make sense for some of these situations or is that mode incompatible with some other setting you need?
Well I never use live view for sports. Live view might be fine for landscapes where you have plenty of time to compose the shot, but for sports you really need to use the viewfinder. Also the phase detect AF points are designed to focus very quickly, which is what you need for fast action.
As you will have seen from the examples I posted yesterday, you don't often focus on a player's face. More commonly the AF system will pick up the ball or the good contrast between a player's shirt and his arm. Quite often the A'F point settles on the back of a player so in this situation facial recognition would be of no use.

Face detection IS available with viewfinder focus on multiple Canon cameras.

And imo, it works very well quite often, but when it misses, it misses, and it will take a second to switch to a different AF-mode.
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Re: Sports shooters: single or expanded AF points?
« Reply #43 on: September 25, 2017, 04:22:12 AM »