1D autofocus settings and a teleconverter

^^Gord^^

^^Gord^^

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Hi all,

I'm using a 1D Mark II with a Sigma 300 f/2.8 and at times a Canon 1.4x II TC. As expected, I'm taking a big hit on my auto focus speed when I have the TC on.

When taking photos on a plane coming towards me it all works fine but as the plane passes me and I turn to pan it I'm losing AF lock.

My usual settings are....

AI Servo
Centre AF point
C.Fn 13 - Set to 0 - 45/Center
C.Dn 17 - Set to 2 - Automatic expand (max. 13)
C.Fn 20 - Set to 2 - Moderately slow
C.Fn 21 - Set to 0 - Disabled

What I'm wonder is if adjusting the AF tracking speed (C.Fn 20) to either 'slow' to attempt to keep the lock or to 'fast' in an attempt to aquire the lock again quickly.

Does anyone have any experience with this? Or any other suggestions?

I've given some though to moving back to a 400 L f/5.6 but decided against it.

Thanks in advance!
 
What happens with your 400L 5.6? Same result?

I know that the TC slows things down a bit, deliberately according to Canon, but my initial impression is that the camera simply can't keep up with a jet flying past.

When the plane is at distance, even though it is moving fast, it may even be at infinity or at least the focus doesn't have to move very far and there is plenty of depth of field. When when it gets close, the thing is changing distance at a phenominal rate. I supsect that the AF will have difficulty in predicting where exactly to focus next, and quite likely will not be able to move into position fast enough.

Speed also depends on the aperture with a big lens like the 300 2.8 and if you're shooting at f/11 or something high that will make a difference. Even at f/8 the aperture blades have to move a long way, after predictive AF has done its stuff, but before the shutter can open. It waits for the aperture to close down.
 
The 400 L f/5.6 handles it fine.

From what I've read the 1.4x TC slows the AF by about 55% which is a pretty big hit! It's mean to make it more accurate.

My take on the situation is the same as yours but I'm trying to minimise the impact if possible.

With the 300 f/2.8 + TC I tend to be between f/5 and f/8.
 
CF20 has no impact on tracking speed I have all my cameras set to as slow as they will go.
 
Don't forget that on a 1 series body there more cross type AF points in use with lenses F2.8 or faster, with the 1.4 tc you lose some of this sensitivity.
 
I also remember a known glitch where the focus would sometimes just freeze, mine did it and I just let go of the focus button and start again.
 
^^Gord^^ said:
The 400 L f/5.6 handles it fine.

From what I've read the 1.4x TC slows the AF by about 55% which is a pretty big hit! It's mean to make it more accurate.

My take on the situation is the same as yours but I'm trying to minimise the impact if possible.

With the 300 f/2.8 + TC I tend to be between f/5 and f/8.
Click to expand...

If the 400L 5.6 does it fine, then it must be the slower action of the TC combo, obviously. I suspect all that you can do is raise the ISO and hope that a bit more depth of field will cover the error. I'm not familar with 1-Series custom functions so I'll shut up ;)
 
Thanks for the replies.

malla1962 said:
CF20 has no impact on tracking speed I have all my cameras set to as slow as they will go.
Click to expand...

You're splitting hairs, speed / sensitivity it's in effect the same thing.

Les McLean said:
Don't forget that on a 1 series body there more cross type AF points in use with lenses F2.8 or faster, with the 1.4 tc you lose some of this sensitivity.
Click to expand...

True, but I'm shooting with the centre focus point only with or without the TC so I'm not really making use of the other cross type AF points.

I think using all the focus points would increase the chance it would try to lock something else and make the problem worse.
 
^^Gord^^ said:
Do you want to clarify that so more?

Are you saying that the setting doesn't take affect when you are in AI Servo mode but does in other AF modes?

Or are you picking up on my use of the word speed rather than sensitivity?
Click to expand...
What I am trying to say is weather you have it set to fast or slow it will not affect the tracking of your subject when locked on.
 
Absolutely agree but I'm losing my AF lock, that is my entire issue. Either the AF can't calculate it fast enough with the TC slowing the process down, the AI Servo is miscalculating where to set the focus when the plane has changed from being head on to side by side or when I'm panning I'm losing my AF lock.

The last one is where I'm considering C.Fn 20 might help. Either by setting it slow enough to not refocus or high enough to quickly research for a lock (combined with the expanding AF from C.Fn 17).
 
Custom function 20 on a 1dmk2 does not affect the AIservo tracking speed.

extract from manual

C.Fn-20 AI SERVO tracking sensitivity

0: Standard
1: Slow / 2: Moderately slow
Prevents the autofocus from being thrown off by any obstacle passing between the camera and subject.
3: Moderately fast / 4: Fast
Effective when you want to consecutively photograph multiple subjects
located at random distances.

This Custom Function does not affect the AI Servo AF tracking speed.

Its possibly a combination of the sigma and converter, sigma hsm motors are quite a bit sloweer than canon usm motors. The combination of sigma and tc may just be enough to slow the AF down enough to miss focus.
 
The problem you have is the same I experience with the canon 300mm f4 and 1.4x TC which will hunt if you lose focus off the aircraft (which is easily done with one focus point). I did use the C.Fn-04 Shutter button/AE lock button Set 2, but couldn't get on with it, so just half press shutter to obtain focus.

AI Servo
Centre AF point
C.Fn 13 - Set to 0 - 45/Center
C.Dn 17 - Set to 2 - Automatic expand (max. 13) (TTL. of 7 AF points)
C.Fn 20 - Set to 2 - Moderately slow (0 - Standard)
C.Fn 21 - Set to 0 - Disabled

Because we're using the centre focus point and lose autofocus speed because of the TC, I tend when I know where the aircraft is going for panning (say in the loop) to keep focus point on aircraft and shutter half pressed, but when I'm unsure of the direction (like at airshows), I keep aircraft in focus by picking it up at the start of the pan and only half press shutter a short time before when I know I want to take the shot thus limiting the chances of losing camera lock. You could also light up more than 1 focus point on the 1D, which I've done for cars, not sure if you lose the expansion facility when selecting 2 autofocus points

Peter
 
mho said:
Custom function 20 on a 1dmk2 does not affect the AIservo tracking speed.

extract from manual

C.Fn-20 AI SERVO tracking sensitivity

0: Standard
1: Slow / 2: Moderately slow
Prevents the autofocus from being thrown off by any obstacle passing between the camera and subject.
3: Moderately fast / 4: Fast
Effective when you want to consecutively photograph multiple subjects
located at random distances.

This Custom Function does not affect the AI Servo AF tracking speed.

Its possibly a combination of the sigma and converter, sigma hsm motors are quite a bit sloweer than canon usm motors. The combination of sigma and tc may just be enough to slow the AF down enough to miss focus.
Click to expand...

You are correct, the word speed in my post is a little vague. The time taken to calculate the autofocus takes the same so it doesn't directly control the performance but the sensitivity controlled by C.Fn 20 will affect how fast (or slow) it will look for a new AF lock or discard the current one. As I see it this is a part of the tracking performance.

I know I'm asking a lot from the kit, I might be asking too much, but if I can improve matters I'll be happy to take the shots I can get.

pete.rush said:
The problem you have is the same I experience with the canon 300mm f4 and 1.4x TC which will hunt if you lose focus off the aircraft (which is easily done with one focus point). I did use the C.Fn-04 Shutter button/AE lock button Set 2, but couldn't get on with it, so just half press shutter to obtain focus.

AI Servo
Centre AF point
C.Fn 13 - Set to 0 - 45/Center
C.Dn 17 - Set to 2 - Automatic expand (max. 13) (TTL. of 7 AF points)
C.Fn 20 - Set to 2 - Moderately slow (0 - Standard)
C.Fn 21 - Set to 0 - Disabled

Because we're using the centre focus point and lose autofocus speed because of the TC, I tend when I know where the aircraft is going for panning (say in the loop) to keep focus point on aircraft and shutter half pressed, but when I'm unsure of the direction (like at airshows), I keep aircraft in focus by picking it up at the start of the pan and only half press shutter a short time before when I know I want to take the shot thus limiting the chances of losing camera lock. You could also light up more than 1 focus point on the 1D, which I've done for cars, not sure if you lose the expansion facility when selecting 2 autofocus points

Peter
Click to expand...

I'm a previous 300 f/4 L IS owner as well Pete and did also try it with a TC.

The place I really notice it is Cad East. Shooting the aircraft on the approach produces some very sharp results - example - but when they make the first turn in the valley the AF starts to struggle and when they make the second turn to straighten up the lock is completely gone.

The AF expansion does come with an AF hit (where it calculates if to expand or not) but the results it produces should compensate this hit. I might try disabling it and using one or two AF points instead and fast tracking sensitivity.
 
^^Gord^^ said:
When taking photos on a plane coming towards me it all works fine but as the plane passes me and I turn to pan it I'm losing AF lock.
Click to expand...

A friend of my said that you can't have you cake and eat it.

I think you trying to do too much and thats why your failing to get shots when panning. You've set up to get head on shots, then at last minute try to pan as well. Personally I would try and concentrate on one or the other.

It's also a mind set.....aircraft comes into view take image, maneuvers, take image, all fine, but you not really set up to pan, and your mind is still concentrating on head on shot, then you decide pan, and it happens all to quickly and your not getting you panning shots. Personally stick to one or the other, try to do both gets you in the situation your in.

Peter
 
^^Gord^^ said:
You are correct, the word speed in my post is a little vague. The time taken to calculate the autofocus takes the same so it doesn't directly control the performance but the sensitivity controlled by C.Fn 20 will affect how fast (or slow) it will look for a new AF lock or discard the current one. As I see it this is a part of the tracking performance.

I know I'm asking a lot from the kit, I might be asking too much, but if I can improve matters I'll be happy to take the shots I can get.
Click to expand...

No it doesn't affect how fast it looks for a new focus lock, AIservo constantly keeps accruing focus and then calculating the next position and recalculating the next position all the time while your focus button is pressed, that is the speed at which AF works, factors which change how it reacts if it detects a subject in-between your plane and camera is set by cf 20. so say you have AF on your plane, then a bird passes between you and the plane in effect shortening the distance to object as the bird is the new object cf 20 determines how long the bird has to be in the way of your object before it switches all AF calculations to start from the distance of the bird, but until that predetermine time (set by cf 20) is elapsed AIservo is still calculating the speed and place of the plane. So no it doesn't have an effect on AIservo / AF speed. As this function ONLY comes into play if something passes between you and the tracked object.

The limiting factors of AIservo / AF operation on your kit is the sigma and 1.4x converter, not the camera settings.
 
mho said:
No it doesn't affect how fast it looks for a new focus lock, AIservo constantly keeps accruing focus and then calculating the next position and recalculating the next position all the time while your focus button is pressed, that is the speed at which AF works, factors which change how it reacts if it detects a subject in-between your plane and camera is set by cf 20. so say you have AF on your plane, then a bird passes between you and the plane in effect shortening the distance to object as the bird is the new object cf 20 determines how long the bird has to be in the way of your object before it switches all AF calculations to start from the distance of the bird, but until that predetermine time (set by cf 20) is elapsed AIservo is still calculating the speed and place of the plane. So no it doesn't have an effect on AIservo / AF speed. As this function ONLY comes into play if something passes between you and the tracked object.

The limiting factors of AIservo / AF operation on your kit is the sigma and 1.4x converter, not the camera settings.
Click to expand...
Bang on.(y)
 
I did wonder if malla1962 was trying to make that point mho, hence why I ask him to clarify. When I read the Canon whitepaper on it, it does exactly say what you are saying for Moderately Slow and Slow but it then changes it's description for Moderately Fast and Fast.

C.Fn 20-1 (“Slow”) programs the AF to remain at the most recently focused distance for up to 1 second while an obstacle is blocking the original subject.
Click to expand...

C.Fn 20-4 (“Fast”) programs the AF to refocus on a new subject approximately 0.125 seconds after the original subject is no longer being tracked.
Click to expand...

I understand the point you are making about AI Servo and how it calculates it's next focus point but that is after it's focused for the first time. If it loses the focus then it does start to hunt.
 
^^Gord^^ said:
I understand the point you are making about AI Servo and how it calculates it's next focus point but that is after it's focused for the first time. If it loses the focus then it does start to hunt.
Click to expand...

A symptom of the sigma's motor and the effect of the 1.4 conv.
 
Presumably your centre focus point is on the planeall the time you can see it through the viewfinder?

If you are up a hill and there is nothing likely to come between you and the plane I would try multipoint focusing as it might then transfer the lock from one point to another but will always try to focus on the nearest subject? Worth a try.

I also think it's the addition of the TC at fault here but it could be the Sigma isn't up to it? It would be interesting to see if the same happened with a Canon 300mm 2.8!
 
mho said:
A symptom of the sigma's motor and the effect of the 1.4 conv.
Click to expand...

I'm not sure at this stage if it's the lens not being able to react fast enough or if the auto focus isn't able to keep up / correctly calculate where the focus should be.

admirable said:
Presumably your centre focus point is on the planeall the time you can see it through the viewfinder?

If you are up a hill and there is nothing likely to come between you and the plane I would try multipoint focusing as it might then transfer the lock from one point to another but will always try to focus on the nearest subject? Worth a try.

I also think it's the addition of the TC at fault here but it could be the Sigma isn't up to it? It would be interesting to see if the same happened with a Canon 300mm 2.8!
Click to expand...

I use the centre focus point and there shouldn't be anything between me and the subject. 45 point selection is worth a try, I'll add to my list to try next time I'm out.

Without the TC with the same lens and same settings I don't have the issue. It's without doubt the addition of the TC. Would the Canon fair better? I'd guess so but I still think it would suffer to some degree. Sadly, the lens price rises stopped me from picking one up in Jan so it will be some time before I get the chance to find out.
 
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