My (seemingly) never ending Focus woes ... BIF advice needed

[Portrait_Moments_Photogra]

it seems like you forgot an IMPORTANT THING

pls review your manual at page 73 and page 77

61 point automatic selection AF both in A+ and AI Servo Modes

dont worry, there's nothing wrong with your 5D3, just wrong user settings.

we all experience it - one way or the other.

[jp121]

There's a very good video on B&H Learn in Depth on Canon AF. It comes in 3 parts.
http://www.bhphotovideo.com/indepth/photography/tips-solutions/look-canon-autofocus-system-part-1

It explained to me what each Focus points looks for & what is special about Cross-type points. How to use servo etc

I think the problem is that the car has no contrast points for the AF to lock on to. Or more specifically aiming all the focus points at the car is not the right way. You have to aim one of the little boxes at a point with contrast that contains either a horizontal or vertical line.

Plus you have to give the AF system a moment to focus & lock the target.

[ddl]

At about 19 minutes in the first B&H video it says for AI Servo that the camera starts to track with the CENTER AF point and if the subject moves off center the camera now uses the outer AF points to continue to follow it.

[jonathan7007]

All,
This is a valuable thread that I will revisit with manual and my own Mk3 in hand, because I have had focus problems and inconsistencies with my Mk3 that have lost shots. I have spoken to other pros with the same experience.

Absent in this thread is the caveat that there may be "focusability" (made-up word) inconsistencies between Mk3 bodies. Manufacturing? Who knows. So CR posters reply with their bodies' performance in described situations (extremely valuable feedback) but it can hard to determine to scientific tolerances where the problem lies with so many variables.

As a CPS member I sent my Mk3 to Canon once (expensive action where I live) with documentation and I got a "could not reproduce..." letter. I know that recreating the shooter's exact conditions and issue is nearly impossible. If that's the criteria it will be tough to get satisfaction, but that is reasonable -- or more exactly "realistic" -- for a manufacturer to require.

So I will
1. continue to learn more about my Mk3, because I recognize that that *I* may be the problem and
2. probably sell my body to someone with lower AF expectations/needs and try not to agonize over the cash lost in swapping copies. (I bought mine early summer so no discount)

This post is also a thank you to all who post here, especially the regulars that shoot tough situations -- with professional-level expectations -- all the time, like bdunbar, PWP, neuro, others.

jonathan7007

[East Wind Photography]

One other thing to point out is that the AF system on an camera will have trouble if the subject you are focusing on is too small.  As In the example below of the car going through the field of view, if the car were bigger as in using a telephoto lens, the AF would be more accurate.

I run into issues with catching birds in flight if they are too far away and on noisy backgrounds.  You just have to understand the limitations or use a longer lens when you can.

I don't believe the camera is at fault.  You can try in such circumstances to use a single focus point and use the joystick to get the AF onto the subject be it the grill of a car or the eye of an eagle.  The issue is not unique to the 5d3.

[bdunbar79]

I did all that stuff.  It still doesn't work that well.  My cases aren't in good light; mine are in bad lighting.  I concede that I may be asking the camera to do something unreasonable.  Even with cross-type only points in AI Servo mode, even though the diver is closer to me than anything, down throughout the dive the AF point will still go back and hit the wall, for some unknown reason, at least twice.  The reason is because the wall is grayish/white and is lighted up more than the diver.  This will confuse any AF system.  To the OP, you have to pay attention to back-lighting too.

Good discussion so far.

If you have manually selected the AF point and are subject tracking, there's no way for the camera to switch the AF points regardless of the contrast.  It will try to focus using your selected point.

Who said I selected one point?  If I remember correctly, I stated I was using zone with only cross types selected, auto AF point selection.

[bdunbar79]

Yep it you have a high contrast horizontal object in the background and an AF point is sensitive to that it will take priority over the low contrast vertical edge of the diver.  I either use spot AF or ALL AF points and lock using the center point initially and let the AF system track the edges for me.

I'll add it's still not 100% unless I use center point only and track on the swim shorts.

1DX does the same thing.  I shot a diving meet last night and zone AF, no matter which tracking case, couldn't lock on the diver all the way through.  It would focus on stupid things in the background every 3rd shot.  I was in extremely low light, however, and that no doubt contributed to this.

YES!

[christianronnel]

At about 19 minutes in the first B&H video it says for AI Servo that the camera starts to track with the CENTER AF point and if the subject moves off center the camera now uses the outer AF points to continue to follow it.

Personally, I prefer to track the subject manually rather than relying on the camera to switch AF points.  I seem to get better result that way.  Most of us naturally track subjects the same way anyway, so why not just choose a fixed AF point?  Even the presenter stated that Auto AF point selection is convenient for some situations but with lots of limitations.  I think sports shooters should really practice selecting their AF points and subject tracking.

Who said I selected one point?  If I remember correctly, I stated I was using zone with only cross types selected, auto AF point selection.

Sorry, I wasn't clear.  I was actually suggesting to manually select AF point next time instead of auto AF selection.

[ddl]

I track manually with the camera as well rather than relying on the focus points to follow the subject.

I posted this as I thought it might help the OP with his problem.

[bdunbar79]

At about 19 minutes in the first B&H video it says for AI Servo that the camera starts to track with the CENTER AF point and if the subject moves off center the camera now uses the outer AF points to continue to follow it.

Personally, I prefer to track the subject manually rather than relying on the camera to switch AF points.  I seem to get better result that way.  Most of us naturally track subjects the same way anyway, so why not just choose a fixed AF point?  Even the presenter stated that Auto AF point selection is convenient for some situations but with lots of limitations.  I think sports shooters should really practice selecting their AF points and subject tracking.

Who said I selected one point?  If I remember correctly, I stated I was using zone with only cross types selected, auto AF point selection.

Sorry, I wasn't clear.  I was actually suggesting to manually select AF point next time instead of auto AF selection.

Oh ok, sorry for the confusion.

Here's another problem I thought of.  Suppose you are again shooting swimming.  You want to shoot the swimmers at the start of the race of a backstroke race.  You focus on the back of the head of the swimmer, who is facing away from you.  The "beep" goes and you want to shoot the swimmer from release all the way back and into the water.  Since the swimmer's head will come back towards you rapidly, I have not been able to get this sequence all in focus with a burst mode, because the swimmer moves so quickly so it appears the AF cannot keep up.  Perhaps this is another impossible task, but it's interesting that I tried to do it, with failure of course .

[christianronnel]

Here's another problem I thought of.  Suppose you are again shooting swimming.  You want to shoot the swimmers at the start of the race of a backstroke race.  You focus on the back of the head of the swimmer, who is facing away from you.  The "beep" goes and you want to shoot the swimmer from release all the way back and into the water.  Since the swimmer's head will come back towards you rapidly, I have not been able to get this sequence all in focus with a burst mode, because the swimmer moves so quickly so it appears the AF cannot keep up.  Perhaps this is another impossible task, but it's interesting that I tried to do it, with failure of course .

I'm not exactly sure, but with back-stroke, the head never goes under water, right?  Is that a similar scenario as a runner running towards you?  If it is, I have been able to capture runners well with just the settings I described earlier, in AI servo and with the focus point selected where I think their head would be.

Here's a cheetah running towards me.  I took it with my measly 70-300L so subject in the frame is far too tiny to post but most of the images in the entire series look in focus.  That cheetah was clocked at just over 50MPH on that run, surely a swimmer would be slower.  I don't know  how hard would it be to track if the lens is at f2.8.

m a j a n i @ 50+ miles/hour by Christian Ronnel, on Flickr

Africa's spotted sprinter by Christian Ronnel, on Flickr

[bdunbar79]

Excellent shots!!

I didn't explain my backstroke situation clearly, as I reread it and I couldn't even figure out what I was talking about.  My problem was at the start of the race, where the swimmers are stationary, and then when the gun goes off, they quickly "snap" back, flip, and head into the water.  I was trying to lock focus on the back of the head, stationary, then the gun goes off and they flip back rapidly, and was not able to keep focus since they flipped back towards me.

Your settings work really well for backstroke swimmers, yes, during the race.

[christianronnel]

Thanks!

I guess I'm still confused or I really don't know what I'm talking about.  If I remember correctly, with back-stroke, at the beginning of the race the swimmers are already facing the wall.  Depending on which end of the pool you may be located, they either start facing you (closest) or you have the back of their heads (far end).  If I understand you correctly, you are on the far side of the pool.  In that case you focused on the back of the head and when they kick, you see the top of the head to their chin depending on the height you were shooting.  In that case I'm not sure if there's a difference between focusing on the back of the head and track to something like a face.  My guess would be that it should be the same.  If you are located near the starting point (I'm not sure if that's even allowed) then I can understand what you mean when they flip and kick when they reach the other end of the pool.  In that case, I'm not sure I'll do anything different.  I must admit I'm curious now.  It would be cool to shoot a swimming competition.  I've only assisted on cycling and running races.

[bdunbar79]

Yeah, I hadn't really done any swimming before either.  I was straight down the pool at the opposite end of the swimmers.  I wasn't allowed near the start due to F.A.T. at the start and finish line.  I'm going to look at my shots and think about this some more.  Thanks.

[bjd]

There's a very good video on B&H Learn in Depth on Canon AF. It comes in 3 parts.
http://www.bhphotovideo.com/indepth/photography/tips-solutions/look-canon-autofocus-system-part-1

It explained to me what each Focus points looks for & what is special about Cross-type points. How to use servo etc

I think the problem is that the car has no contrast points for the AF to lock on to. Or more specifically aiming all the focus points at the car is not the right way. You have to aim one of the little boxes at a point with contrast that contains either a horizontal or vertical line.

Plus you have to give the AF system a moment to focus & lock the target.

HI, thanks for the link, I'll certainly be studying the videos today. 
As I have focus problems with BIF I tried the, what I hoped would be a simpler, situation for the camera  with the moving cars. I only posted a few shots here, but as the car moves across the center of shot, I had assumed that one of the center points would lock on somewhere (as various parts, lines etc. cross) and it would at least follow from then on towards the left of frame.
Having the cars cross at an angle to me and not at 90° would I thought have given the Camera the time needed. We'll see.
Thanks to everyone who contributed here.
Cheers Brian