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I've had some problems with a Canon lens mis-focussing (see examples here). I asked Canon about the problem (via my "pro rep") and got this absurd reply. WTH!
Canon support gone bad
- Thread starter Neil Pho
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+1 ^^ to what Elliot says on the surmise that Canon has correctly interpreted your example images!
As such, then more importantly why do you think the reply is so absurd?
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Do you actually believe that AI Servo will "never lock onto a steady subject", or are you "trolling" me?
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The performance level of AI servo is body dependant and also may vary lens to lens on the same body.
IMO using that mode with static subjects is open to issues and cameracraft errors, as such needs to be used with caution.
I am on my smartphone so have no idea via EXIF of body details.
In any of my replies YMMV.
IMO using that mode with static subjects is open to issues and cameracraft errors, as such needs to be used with caution.
I am on my smartphone so have no idea via EXIF of body details.
In any of my replies YMMV.
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Sometimes what manufacturers say does not stand up in "real world" usage.......a little like car fuel consumption figures.
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Yes, I do. AI servo is for moving subjects, not static subjects. If AI servo is good for both static and moving subjects why do Canon give you three focus modes?
Did you take Canons advise and try with one shot AF or just come on here to moan?
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sk66
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I find that idea completely absurd...
I use continuous AF all the time w/ static subjects... the only thing I've ever noticed is that it may occasionally "recenter/recheck" AF if it's been active and stagnant for a while. And it will chatter/stutter with every minor camera movement.
I use continuous AF all the time w/ static subjects... the only thing I've ever noticed is that it may occasionally "recenter/recheck" AF if it's been active and stagnant for a while. And it will chatter/stutter with every minor camera movement.
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Is that Nikon or Canon though? Nikon AF-C is actually very good with static subjects.
That being said there are plenty of people using BBF and AF-C with Canon that don't have accuracy issues.
OP take shots using AF-S and take it from there. If they'll still soft you have more fire power so to speak. If not it would suggest that you shouldn't use AF-C (or AI servo as Canon call it) for static subjects as recommended by Canon.
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To be fair you'll probably have more accuracy using BBF if you stop the focus once focus has been achieved. When using the shutter button or if you keep the BBF button depressed, the camera is constantly trying to predict where focus should be, thus may not be correctly focused when taking the shot.
Canon are quite clear what each focus mode is for so I'm not sure why the OP or anybody else is questioning it.
http://www.canon.co.uk/for_home/pro...ital_slr/technologies_features/af_system.aspx
If you want to focus on a static subject and still have the ability to quickly switch modeshen the subject move then you should be using AI Focus AF.
I find it quite acceptable that the Canon tech would ask the OP to test in the correct mode.
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sk66
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Both. While I own Nikon, I have used many Canons and have many friends who own/use them to shoot the same kind of stuff. I can't imagine photographing any kind of sport/wildlife with a camera that couldn't focus on a static subject while in continuous AF.
AI servo simply constantly focuses... if the focus point shifts due to camera movement it will refocus, so if using an f/1.x wide open expect to have issues using it. And depending on how "jittery" you have it set it might be a little better/worse. Switch to One-shot or BBF.
Unless Canon has fixed AI Focus in the most recent models, it's not worth using IMO. At least not for any real speed/action/changes... it doesn't really work.
Looking at the images it looks more like an issue of focus point selection rather than focus servo mode as such.
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Is AI focus the Canon terminology for the AF-A? In which case I never use this on any camera
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No, Canons have that (auto area) as well... Nikon doesn't have anything quite like AI focus.Is AI focus the Canon terminology for the AF-A? In which case I never use this on any camera
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Just looked it up. According to the Canon site AI focus gains focus on a static subject but automatically switches to AI servo if the subject's starts to move, whereas Nikon's AF-A automatically switches between AF-S and AF-C depending on whether the subject is moving or not.
So it sounds like the same kind of thing just implemented differently
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OOPs. None of my Nikons have AF-A... I assumed it was auto point selection.Just looked it up. According to the Canon site AI focus gains focus on a static subject but automatically switches to AI servo if the subject's starts to move, whereas Nikon's AF-A automatically switches between AF-S and AF-C depending on whether the subject is moving or not.
So it sounds like the same kind of thing just implemented differently
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Rightly or wrongly, continuous AF certainly gets the blame for some OOF shots, though looking at the OP's images I'd guess that might be the least likely of several possibilities.
Here's a theory: we know that image stabilisation gets upset on a tripod. When the system is hunting for movement but the camera is stationary, a feedback loop develops in the circuit and produces erroneous corrections. Hence tripod-sensing etc.
Continuous AF is doing the same thing, constantly looking for distance changes, but when both the camera and the subject are completely stationary (actually quite a rare condition) then the system get itself in a twist in the same way as image stabilisation can. Very likely to be camera/model dependent.
Here's a theory: we know that image stabilisation gets upset on a tripod. When the system is hunting for movement but the camera is stationary, a feedback loop develops in the circuit and produces erroneous corrections. Hence tripod-sensing etc.
Continuous AF is doing the same thing, constantly looking for distance changes, but when both the camera and the subject are completely stationary (actually quite a rare condition) then the system get itself in a twist in the same way as image stabilisation can. Very likely to be camera/model dependent.
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Sounds logical.
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I'm sorry Richard, but that sounds like a theory to fit a problem tbh
... if the s/w engineer that wrote the algorithm did it like that they need shooting. In essence it should be a simple case of if nothing has changed then do nothing ... I know that not all s/w engineers are created equal though It does seem odd that a continuous focus mode cannot focus on a static subject though, that is if the Canon rep's response is to be believed. I don't regularly shoot with Canon so have no real way of trying it. Certainly with Nikon AF-C works just fine on static subjects so would expect Canon to be the same.
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I'm sorry Richard, but that sounds like a theory to fit a problem tbh
It does seem odd that a continuous focus mode cannot focus on a static subject though, that is if the Canon rep's response is to be believed. I don't regularly shoot with Canon so have no real way of trying it. Certainly with Nikon AF-C works just fine on static subjects so would expect Canon to be the same.
LOL Yes, that's exactly what it is. Might be right though
I think it is a recognised problem though, at least with some cameras/lenses in some situations, if rare. There must be a technical explanation for it, maybe newer cameras have got it sorted now.
I've never noticed it, but then I never use continuous AF mode. I find it simply irritating when it judders around for no reason, and then when the AF point accidentally strays on to the background, it immediately goes way out of focus and you have to start again. When I want continuous focusing with a moving subject, I just keep my thumb on the back-button and there it is, on demand.
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Can't you choose how 'sticky' the AF point is on Canon so that if it momentarily strays off the subject it won't shift focus?LOL Yes, that's exactly what it is. Might be right though
I think it is a recognised problem though, at least with some cameras/lenses in some situations, if rare. There must be a technical explanation for it, maybe newer cameras have got it sorted now.
I've never noticed it, but then I never use continuous AF mode. I find it simply irritating when it judders around for no reason, and then when the AF point accidentally strays on to the background, it immediately goes way out of focus and you have to start again. When I want continuous focusing with a moving subject, I just keep my thumb on the back-button and there it is, on demand.
Canon Bob
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The most obvious difference in application is that AIservo does not need focus confirmation before releasing the shutter. The shot will be taken whatever state the focus is in and the only configurable variable is the time before the shutter release. On the other hand, one shot AF does require focus confirmation before the exposure is started.
I'm sure that we all use AIservo for static shots occasionally and it's more often that not a success. But based on configurable delays, aperture related DoF and lens drive speed then there re numerous factors that can conspire to nobble us.
Bob
I'm sure that we all use AIservo for static shots occasionally and it's more often that not a success. But based on configurable delays, aperture related DoF and lens drive speed then there re numerous factors that can conspire to nobble us.
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I'm not familiar with Canon but with Nikon you can choose whether shutter is set to focus (meaning it will not take a picture unless focus has been obtained) or release (will take the shot as soon as the shutter is pressed whether in focus or not) for AF-C (Nikon's AI servo), is there not this option on Canon?
Canon Bob
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In AIservo you can vary the relationship between focus and release (timewise) but it will always release the shutter after the configured time has expired.
Bob
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Just a quote from Canon's North American CEO when this was raised a while back;
AI Servo AF allows photographers to release the shutter at will, regardless of whether focusing has been completed or not. This is intentional, in order to allow the photographer to prioritize capturing the peak moment regardless of focusing status. The trade-off is the fact that there is no guarantee that the focus will be sharp on a stationary subject in AI Servo AF, especially during handheld photography at close range with shallow depth of field. Under these specific conditions (one more time for emphasis, I am saying Stationary Subject, handheld photography at close range with shallow depth of field), One-Shot AF is a more reliable focusing method because it locks focus while AI Servo does not.
Bob
AI Servo AF allows photographers to release the shutter at will, regardless of whether focusing has been completed or not. This is intentional, in order to allow the photographer to prioritize capturing the peak moment regardless of focusing status. The trade-off is the fact that there is no guarantee that the focus will be sharp on a stationary subject in AI Servo AF, especially during handheld photography at close range with shallow depth of field. Under these specific conditions (one more time for emphasis, I am saying Stationary Subject, handheld photography at close range with shallow depth of field), One-Shot AF is a more reliable focusing method because it locks focus while AI Servo does not.
Bob
sk66
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Yes, depending on the Canon model there are three settings. One is for tracking sensitivity (delay refocus when lost), another is for changes in distance, and the last is for lateral changes in position (focus point switching). There are also a bunch of "preset scenarios" you can choose for these settings. If they are set high, it becomes a lot more "twitchy." If set to minimums it becomes rather stable.
You combine those settings with the number of AF points you want to allow it to use (single, expansion, zone, auto). If set to a single point, then it's not going to move at all. If set to multiple points it *should* only move if the point of focus (subject) moves. But with continual/repeated camera movement it will continually refocus and start to try to predict where focus "will be"... if it gets it wrong then there will be misfocus.
But nothing like in the OP's examples IME/O... I suspect it's more an issue of auto point selection being enabled to some large degree (zone or auto).
Edit: it's a lot like Nikons... some cameras have no settings, some have limited settings, and others have more settings. I don't recall what the options are on the 5D...
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looking at the two sample images ,and seeing the motorbike coming towards you in the second shot with its headlight on ,i wonder if the problem lies with lack of light both photos do seem rather lacking in sufficient light .
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This comment doesn't seem to be backed up by this from the manual Bob.
22: AI Servo
AI Servo 1st image priority
You can set the AF operation characteristics and shutter-release timing for the first shot with AI Servo AF.
: Equal priority
Equal priority is given to focusing and shutter release.
: Release priority
Pressing the shutter button takes the picture immediately even if focus has not been achieved. Useful when you want to give priority to capturing the image rather than achieving focus.
: Focus priority
Pressing the shutter button does not take the picture until focus is achieved. Useful when you want to achieve focus before capturing the image.
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I've been ferreting through the archives and it seems that there's a difference in configuration (and application) between those bodies having the AF "Case" configurations and those that don't.
By model this would suggest that the 1Dx's, 5DS/SR's, 7D2's, 5DIV's and 5DIII's (with the current firmware) operate using the pre-requisite for focus (if so configured) whilst all the others release the shutter on demand (delayed by the configured response time).
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That would make sense Bob. I've certainly had my 1DX not releasing the shutter because it's not in focus.
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I took my camera and lens in for service with Canon. The replaced the USM assembly and main PCB in the lens.
I've always used AI Servo and BBF as that gives me maximum flexibility. One-Shot seems more for people who want to focus-recompose using the shutter release.
I do have the camera set for maximum focus priority and Canon service commented that the shutter should not have released in this case.
I've always used AI Servo and BBF as that gives me maximum flexibility. One-Shot seems more for people who want to focus-recompose using the shutter release.
I do have the camera set for maximum focus priority and Canon service commented that the shutter should not have released in this case.
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