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Author Topic: 1DX - Ai Servo Issue - Low light focus failure! Final Update 05/09/12  (Read 37166 times)

Sycotek

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #60 on: August 01, 2012, 09:33:22 PM »
Thanks to all that have attempted to re-create this:

It's a given that the unit will not focus on -2ev low light via Ai-servo, that's only where the investigation started, if anythig the servo has issues around 1ev.

The real issue initial target lock (first frame) failing under low light - low light as in a normal light in a normal room trying to lock on a face.

7D has Ai-focus which I never use - I was comparing Ai-servo against the 1dx Ai servo. With that said the 7D af points are 4 times as large so target acquisition should be faster by default in low light.

I digress: try working in a normal room with an over head light and try locking on a persons face at 3fps and at 12fps with all points on and first point priority and attempt to lock on the targets face (say 180-200mm from 2m away). Now try an notice just how much faster 3fps is in terms of the af points "dancing" on the targets face.

At 12 fps majority of the time it drives my lens and locks up - if I rack the lens to 0 and attempt to focus the lens won't even rack... At 3-10fps the lens racks (actually tries to focus and gets a lock)

Standard 60w light in a 4x4 room isn't exactly low light ESP considering my gf is white skinned with dark hair and eyes.

The 7D regardless of frame rate gives me the initial lock immediately under the same conditions.

I here what you are saying but my 1DX doesn't have problems locking on target at -1ev like yours while in Ai Servo.  It only has issues at extremely low light coupled with low contrast with a static object.  12FPS works just fine for me in Ai Servo as I cannot reproduce your specific issue.  This leads me to believe there is something else going on here.  Perhaps a bad batch from Canon, but I cannot say.  All I know is what I have posted above.

Thank You! this is the first hint that it may be isolated!

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #60 on: August 01, 2012, 09:33:22 PM »

Richard Lane

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #61 on: August 01, 2012, 09:43:38 PM »
Hi Richard, Thanks for replying :)

The original issue was the Ai Servo and contrast in low light - correct, there is a definite discrepancy between ai-servo and one shot ability to focus on objects in low light - but the reason for it being an major issue (to me anyway) is you can't track what you can't lock onto initially: if the lens doesn't rack or the lens racks to infinity and stops when trying lock onto an object - stationary or otherwise - then you can't track that object to start with. Example - this initial became apparent when trying to track my cousin moving around the house, with a fair amount of house lights on.

My camera exhibits this issue in lighting conditions that it should have no issue in (the 7D for example locks regardless) - same as justaphotographer and the in-store demo unit. However that inability to lock onto the target isn't noticed when enabling 10 fps or lower, there is no issue with re-racking the lens and the af points move over the object at a noticeably higher rate then at 12 fps.

I do apologise for the confusion - I hope this is a little clearer.

Thanks for clarifying.  Sure, it would be nice to get that first point locked in.  However, I didn't seem to have a problem focusing on an neutral object and getting the initial focus point to lock on, with only a 75 watt bulb in a table lamp in the corner of the master bedroom.

It's interesting that your 7D doesn't have a problem with this.

What AF case scenario are you using,  Default Case 1?  I will say that my 1DX doesn't exhibit the behavior that your describing.  I'm using Case 1 at the moment.

After-all, it's a very expensive camera so it's good that your putting it through its paces to make sure that everything is working as it's supposed to.
« Last Edit: August 02, 2012, 04:09:19 PM by Richard Lane »

Sycotek

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #62 on: August 01, 2012, 10:14:55 PM »
My way of thinking is i need to know where my gear is going to fail before it fails and costs me $$$.

I trust my 7D as for 2 years and 100K+ clicks still going strong - I know what conditions that body will fail me and I know how to get around it.

That's what I am trying to do with the 1DX is find a baseline where the gear gives out. The problem is the baseline is not that good if the 7D kicks the snot out of it for tracking in low light.

As it is I wouldn't trust the 1DX Ai Servo for a bridal waltz at this point - id get hire out a 1ds3 or 1d4 as i know they work perfectly fine in those conditions.

Edit: Case 1 to answer your question - default with first point focus lock priority (otherwise it will fire regardless of focus)

« Last Edit: August 01, 2012, 10:16:38 PM by Sycotek »

justaphotographer

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #63 on: August 01, 2012, 11:28:54 PM »
Exactly what Sycotek is saying.  I wouldn't normally have too much problem with this failing of the 1Dx in low light/contrast AI-SERVO tracking except for the 4 reasons below.

1.  In the same poor light/contrast situation my older 5D2, 5D Classic and 7D with center point all track in AI-SERVO just perfectly fine (in fact they seem to be as good in AI-SERVO as they are in ONE-SHOT under these conditions).  Whereas the 1Dx in the same exact condition totally craps out.  This seems pretty unacceptable given that it's AF is pretty amazing in every other way.

2.  The fact that when I change the Frames Per Second rate on the 1Dx from 12 to 10 or under, AI-SERVO definitely improves (even though it still totally blows compared to the older 5D2, 5D Classic and 7D).  This causes me to wonder why and if something strange is going on that perhaps Canon can address.  It can't hurt finding things like this out so that people much brighter than me at Canon might make our cameras better and better with firmware updates or whatever they need to to get the job done.

3.  Third, if this was in situations that were so inhumainly dark that nobody should ever even attempt to take a photo then I could just move on and just say that nothing is perfect.  However, where the 1Dx AI-SERVO fails is in moderately dark and low contrast situations.  In my line of work I have need of tracking subjects in a single lamp lighting situation and as it stands the 1Dx camera in AI-SERVO mode cannot be trusted for that.  Like Synotek I just need to know where the baseline is.  However, if that baseline totally sucks compared to Canon's other older cameras I think this is something that should be addressed.

4.  Lastly, in my experience this does not seem to be highly isolated.  My 7 friends and I (all with 1Dx and all received at different times, from different places and from different countries) have all confirmed this exact behavior on all our 1Dx cameras.  I would like to think it was isolated, but at least for us its 100% 7 for 7.

I'm on assignment now and can only respond sporadically, but I thank everyone for all the great interactions on this and all working together to try and solve this problem.  I trust that Canon folks are really smart and will figure something out soon.  Otherwise, this camera is totally amazing and the best I have ever used---even with this issue.


My way of thinking is i need to know where my gear is going to fail before it fails and costs me $$$.

I trust my 7D as for 2 years and 100K+ clicks still going strong - I know what conditions that body will fail me and I know how to get around it.

That's what I am trying to do with the 1DX is find a baseline where the gear gives out. The problem is the baseline is not that good if the 7D kicks the snot out of it for tracking in low light.

As it is I wouldn't trust the 1DX Ai Servo for a bridal waltz at this point - id get hire out a 1ds3 or 1d4 as i know they work perfectly fine in those conditions.

Edit: Case 1 to answer your question - default with first point focus lock priority (otherwise it will fire regardless of focus)
« Last Edit: August 01, 2012, 11:49:01 PM by justaphotographer »

briansquibb

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #64 on: August 01, 2012, 11:37:19 PM »
Is this using single point/expansion/zone AF?

Sycotek

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #65 on: August 01, 2012, 11:42:54 PM »
Is this using single point/expansion/zone AF?

Any AF mode

Sycotek

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #66 on: August 01, 2012, 11:47:21 PM »
Exactly what Sycotek is saying.  I wouldn't normally have too much problem with this failing of the 1Dx in low light/contrast AI-SERVO tracking except for the 3 reasons below.

1.  In the same poor light/contrast situation my older 5D2, 5D Classic and 7D with center point all track in AI-SERVO just perfectly fine (in fact they seem to be as good in AI-SERVO as they are in ONE-SHOT under these conditions).  Whereas the 1Dx in the same exact condition totally craps out.  This seems pretty unacceptable given that it's AF is pretty amazing in every other way.

2.  The fact that when I change the Frames Per Second rate on the 1Dx from 12 to 10 or under, AI-SERVO definitely improves (even though it still totally blows compared to the older 5D2, 5D Classic and 7D).  This causes me to wonder why and if something strange is going on that perhaps Canon can address.  It can't hurt finding things like this out so that people much brighter than me at Canon might make our cameras better and better with firmware updates or whatever they need to to get the job done.

3.  Third, if this was in situations that were so inhumainly dark that nobody should ever even attempt to take a photo then I could just move on and just say that nothing is perfect.  However, where the 1Dx AI-SERVO fails is in moderately dark and low contrast situations.  In my line of work I have need of tracking subjects in a single lamp lighting situation and as it stands the 1Dx camera in AI-SERVO mode cannot be trusted for that.  Like Synotek I just need to know where the baseline is.  However, if that baseline totally sucks compared to Canon's other older cameras I think this is something that should be addressed.

4.  Lastly, in my experience this does not seem to be highly isolated.  My 7 friends and I (all with 1Dx and all received at different times, from different places and from different countries) have all confirmed this exact behavior on all our 1Dx cameras.  I would like to think it was isolated, but at least for us its 100% 7 for 7.

I'm on assignment now and can only respond sporadically, but I thank everyone for all the great interactions on this and all working together to try and solve this problem.  I trust that Canon folks are really smart and will figure something out soon.  Otherwise, this camera is totally amazing and the best I have ever used---even with this issue.


My way of thinking is i need to know where my gear is going to fail before it fails and costs me $$$.

I trust my 7D as for 2 years and 100K+ clicks still going strong - I know what conditions that body will fail me and I know how to get around it.

That's what I am trying to do with the 1DX is find a baseline where the gear gives out. The problem is the baseline is not that good if the 7D kicks the snot out of it for tracking in low light.

As it is I wouldn't trust the 1DX Ai Servo for a bridal waltz at this point - id get hire out a 1ds3 or 1d4 as i know they work perfectly fine in those conditions.

Edit: Case 1 to answer your question - default with first point focus lock priority (otherwise it will fire regardless of focus)

Agreed - even with the issues - you couldn't pay me to give it back - the shop did ask if i wanted them to hold on to it... I immediately yelled something that made me realise i had become a little too attached to my 1DX so much so it reminded me of golem from lor.

For everything that is wrong with it - there are situations i have been able to shoot in that i once could only dream - i hope canon fixes this issue as it is really a remarkable tool.




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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #66 on: August 01, 2012, 11:47:21 PM »

Richard Lane

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #67 on: August 02, 2012, 12:46:48 AM »
Hey Guys.., great thread and info here!

I did some further testing in low light, low contrast with the gray towel in the bathroom.  I was able to reproduce what you're both saying.  So, that means that in a low light, low contrast situation in AI Servo mode the 1DX had a more difficult time focusing on the towel when it was set to 12 fps, I can confirm this too.  (As a side-note, I was able to acquire focus by using the edge of the towel to create more contrast with it against the white wall behind it.)

Then I switched the 1DX to 3 fps in AI Servo and it took a couple of seconds, but it had a little easier time focusing on the center of the towel with low contrast and low light.   

I also have a MKIV and a 7D, so the MKIV behaved similarly to the 1DX as I had stated in my previous post.  However, the 7D in AI Servo, did seem to have a slight advantage over the 1DX and MKIV in that the 7D did acquire focus on the low contrast center of the gray towel, however it took a couple of seconds, whereas when the 1DX acquired focus with the slower fps, it appeared to do it faster than the 7D (just sayin'). 

All of the cameras acquired focus on the low light/ low contrast center of the towel in One Shot mode.

So, if we combine this confirmation with your above impressions of the 5D, and 5DII, and 7D, as well as the improved focus acquisition of the 1DX and MKIV when slower fps were selected.  We may be able to come to a common theme here, which is the cameras with the slower frame rates, or slower frame rate setting all did a better job when focusing in AI Servo.

Now, we all know that the 5D and 5DII have slower fps then the other cameras, but why would the 7D with its 8fps, acquire focus in low contrast/low light in AI Servo?  I'm not sure if you guys know the answer, but are you aware that "the 7D cuts its 8 fps rate in half to approximately 4fps," during low light situations.  I don't think many people are aware of this limitation of the 7D, as a matter of fact it was one of the main reasons that I upgraded to the MKIV.

To test this out for your self, take the 7D into the bathroom with the light on, then set it manual mode, 1/250sec, f/2.8 and a high ISO and hold in the shutter until you achieve the high fps burst and then turn the light off and you'll see what I mean, as there will be a sudden drop in fps.  Now do the same test with the 1DX and when you shut the light there wont be any drop off in fps and the MKV behaves exactly the same way.  The 7D compromises it's frame rate in order to better assist itself with acquiring focus in AI Servo mode.

So this may be the reason.  I also would like to reiterate that this is only my theory at this point.

I will be interested in hearing what you guys think of this.  This doesn't mean that Canon gets a pass, however it may mean that there are some technological, engineering hurdles to overcome to have a fast frame rate perform well in low light, low contrast situations in AI Servo mode.

Enquiring minds want to know!

Rich

« Last Edit: August 02, 2012, 01:28:56 AM by Richard Lane »

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #68 on: August 02, 2012, 12:54:22 AM »
I noticed it too hunting focus in low light in situations I know then5D MKIII would work... I thougt I was doing something wrong.... Any word from Canon on this?
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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #69 on: August 02, 2012, 01:08:08 AM »
No word from Canon, but if you look at the info provided above, in that the slower fps 5D and 5DII, 7D (which decreases it's own frame rate automatically in low light) and the MKIV and 1DX with slower fps performed better in these AI Servo conditions, then I would say that this is an engineering and design decision.  Even in their user manuals, Canon states that the camera may not perform as expected in low light/low contrast situations.

For others reading this thread, the MKIV and 1DX are awesome cameras, and I don't think there is anything actually wrong with them, and I'm thrilled with bot of them, especially the 1DX so far.

Now, if Canon can improve upon it, then I'm all for it.
« Last Edit: August 02, 2012, 01:09:54 AM by Richard Lane »

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #70 on: August 02, 2012, 03:28:25 AM »
We're talking about 7d and 5d2 here, against the 1d X, wow... this isn't very reassuring to say the least...

What if we compare to the 5d3? I'm not really sure how to test this issue with it, but I tried it against a 7d, just in general, and the 7d didn't stand a chance on any level....
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Richard Lane

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #71 on: August 02, 2012, 07:51:42 AM »
Hello Viggo,

I'll just give a quick summary, so as not to create any panic here.  I believe the reason the 5D, 5DII, and 7D acquired focus lock on the low contrast, low light, "stationary" towel in AI Servo was because they have a slower frame rate (the 7D lowers its frame rate automatically in low light) which seems to put the emphasis on focus acquisition.  The 7D, MKIV, 1DX also have the default feature for first Image focus priority, which also places an emphasis on slower focusing, as opposed to shutter release. We're not yet saying that the 1DX doesn't track well in AI Servo, we're just saying that the first focus lock of a stationary or slow moving subject in low light, low contrast situations is difficult to lock-on when higher than 10fps are in use.

Keep in mind though that when the frame rates of the MKIV and 1DX were lowered they did perform better than the 7D in my testing.  I don't own the 5D or 5DII, so I'm going by others findings with regards to this.  In case people didn't read the whole thread, at least in my test, these findings were occurring in low light, low contrast situations of a stationary object in AI Servo in order to lock on the target prior to it moving, to establish focus lock so that the camera will be ready to begin tracking once the subject started to move. Sycotek wanted to test the threshold limits of the 1DX's ability.

"I will say though, that in my experience in real world shooting with the MKIV, in low light, low contrast situations, and shooting at 10fps, I have never had a problem in AI Servo mode, and the 1Dx seemed to perform similarly under the testing conditions above, however, I haven't had a chance to test it in game situations yet.

Recommendations would be if the MKIV or 1DX couldn't lock on the first frame of a tracking burst in AI servo, then the shooter needs to make sure that they grab an edge of the subject to create more contrast (I do believe that this is common knowledge at this level) for focus lock, once the subject starts "moving" and the distance to the camera increases or decreases rapidly then this is supposed to aid the camera in AI Servo tracking.  The other point here, would be to lower the fps to less than 10fps if a problem did arise in real world shooting situations.

I think a good analogy would be if you had 2 race cars going through a slalom course, lets say that one car was limited to 50mph (7D) and the other car was limited to 100mph (1DX).  The drivers were told to make it through the course and around the cones as fast as they can without hitting any cones. The 50mph car would have the same chance as not hitting any cones as the 100mph car, because it's up to the drivers to not exceed the limits of the cars.  Just because the one driver can go 100mph, doesn't mean he should.  He also has the option of going 50mph, or he can go 75mph and win the challenge, or he go 100mph and drive off of the course.

Viggo, in further response to your concern, I don't think that this is as alarming as you think, because the 1DX can be slowed down to meet the needs of the shooting conditions, just because the 5D, 5DII, and 7D are already slowed down by default doesn't necessarily make them better.  I would also be curious to see how the 5DIII behaved, however, I expect that it would behave similarly to the 1DX would if we were to reduce the fps of the 1DX to match the frame rate of the 5DIII.

We also have to be careful when analyzing focus points on the monitor or LCD, because if the camera were to miss focus on the center low contrast point of a subject while holding down the focus button, and then we were to re-compose the shot to the edge of the target, the focus points may look like they were focusing on the higher contrast edge the entire time.

Rich
« Last Edit: August 02, 2012, 08:07:16 AM by Richard Lane »

Viggo

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #72 on: August 02, 2012, 08:31:36 AM »
Hello Viggo,

I'll just give a quick summary, so as not to create any panic here.  I believe the reason the 5D, 5DII, and 7D acquired focus lock on the low contrast, low light, "stationary" towel in AI Servo was because they have a slower frame rate (the 7D lowers its frame rate automatically in low light) which seems to put the emphasis on focus acquisition.  The 7D, MKIV, 1DX also have the default feature for first Image focus priority, which also places an emphasis on slower focusing, as opposed to shutter release. We're not yet saying that the 1DX doesn't track well in AI Servo, we're just saying that the first focus lock of a stationary or slow moving subject in low light, low contrast situations is difficult to lock-on when higher than 10fps are in use.

Keep in mind though that when the frame rates of the MKIV and 1DX were lowered they did perform better than the 7D in my testing.  I don't own the 5D or 5DII, so I'm going by others findings with regards to this.  In case people didn't read the whole thread, at least in my test, these findings were occurring in low light, low contrast situations of a stationary object in AI Servo in order to lock on the target prior to it moving, to establish focus lock so that the camera will be ready to begin tracking once the subject started to move. Sycotek wanted to test the threshold limits of the 1DX's ability.

"I will say though, that in my experience in real world shooting with the MKIV, in low light, low contrast situations, and shooting at 10fps, I have never had a problem in AI Servo mode, and the 1Dx seemed to perform similarly under the testing conditions above, however, I haven't had a chance to test it in game situations yet.

Recommendations would be if the MKIV or 1DX couldn't lock on the first frame of a tracking burst in AI servo, then the shooter needs to make sure that they grab an edge of the subject to create more contrast (I do believe that this is common knowledge at this level) for focus lock, once the subject starts "moving" and the distance to the camera increases or decreases rapidly then this is supposed to aid the camera in AI Servo tracking.  The other point here, would be to lower the fps to less than 10fps if a problem did arise in real world shooting situations.

I think a good analogy would be if you had 2 race cars going through a slalom course, lets say that one car was limited to 50mph (7D) and the other car was limited to 100mph (1DX).  The drivers were told to make it through the course and around the cones as fast as they can without hitting any cones. The 50mph car would have the same chance as not hitting any cones as the 100mph car, because it's up to the drivers to not exceed the limits of the cars.  Just because the one driver can go 100mph, doesn't mean he should.  He also has the option of going 50mph, or he can go 75mph and win the challenge, or he go 100mph and drive off of the course.

Viggo, in further response to your concern, I don't think that this is as alarming as you think, because the 1DX can be slowed down to meet the needs of the shooting conditions, just because the 5D, 5DII, and 7D are already slowed down by default doesn't necessarily make them better.  I would also be curious to see how the 5DIII behaved, however, I expect that it would behave similarly to the 1DX would if we were to reduce the fps of the 1DX to match the frame rate of the 5DIII.

We also have to be careful when analyzing focus points on the monitor or LCD, because if the camera were to miss focus on the center low contrast point of a subject while holding down the focus button, and then we were to re-compose the shot to the edge of the target, the focus points may look like they were focusing on the higher contrast edge the entire time.

Rich

Thank you so much for your thourough reply.  :)

I used to own the 1d4 so I can clearly say the 5d3 kills it completely when it comes to AF, and that is not limited to when using higher framerate. I had my 1d4 set to 5fps in "L" mode, and it still sucked at indoor tracking compared to the 5d3. So my concern was that the 1d X performed similar to the 1d4, which would have been hugely dissapointing considering the 5d3 is that much better.

It must be some kind of math I don't really get, because I don't see why logic would support loss of inital focus could be caused by higher framerate. Sure, between frames, AF would struggle more at 12 fps than at 6 fps, that's a given, but when you lock focus and haven't shot a single frame, why does it matter how many frames the camera can shoot consecutively?

And to be honest I would much rather the 1d X slowed down to 10fps in such a situation causing this issue rather than keeping 12 fps and not work.

Btw, my 5d3, as my 1d4 used to be, is set to focus priority for 1st image and tracking for 2nd frame. I would rather have slower framerate and focus than 40 images oof. Although it REALLY annoyed me the 1d4 wouldn't fire at all when it was dim light.

I also set the camera to keep searching for focus if it couldn't be obtained. I accidently turned that off one time I shot macro and every AF operation just stopped.

Thanks again! After owning a VERY early 1d3, I'm not buying another 7k camera with AF issues.
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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #72 on: August 02, 2012, 08:31:36 AM »

justaphotographer

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #73 on: August 02, 2012, 01:15:25 PM »
Hi Richard Lane,

Thanks for the summery, but let me respond to your quote below, because that isn't really the full story.  You are right that the 1Dx when set to 10fps or slower does track and lock focus better than when it is set to 12fps, however there is still something strange going on, because in my testing in the SAME lighting/contrast conditions where the 1Dx set to 10fps or slower in AI-SERVO fails completely (meaning not slow focus, but can't focus at all), my older 5D2, 5D, and 7D in AI-SERVO mode all focus lock and track just fine.  If my 1Dx set to 10fps or slower focused in AI-SERVO as well as those older cameras then I would be totally okay with this and move on, but as it stand that is not the case.

I think you are right in that there must be some sort of engineering tradeoff going on here, but why is it that in the same light that the 1Dx (at 10fps or slower) totally fails, the older cameras focus and track just fine?  This is what I would like for Canon to either explain or fix if possible.

Otherwise, I agree with you that this is the finest camera I have ever owned.

Hello Viggo,

I believe the reason the 5D, 5DII, and 7D acquired focus lock on the low contrast, low light, "stationary" towel in AI Servo was because they have a slower frame rate (the 7D lowers its frame rate automatically in low light) which seems to put the emphasis on focus acquisition.  The 7D, MKIV, 1DX also have the default feature for first Image focus priority, which also places an emphasis on slower focusing, as opposed to shutter release. We're not yet saying that the 1DX doesn't track well in AI Servo, we're just saying that the first focus lock of a stationary or slow moving subject in low light, low contrast situations is difficult to lock-on when higher than 10fps are in use.
« Last Edit: August 02, 2012, 01:40:32 PM by justaphotographer »

Viggo

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #74 on: August 02, 2012, 01:36:31 PM »
Hi Viggo,

Thanks for the summery, but let me respond to your quote below, because that isn't really the full story.  You are right that the 1Dx when set to 10fps or slower does track and lock focus better than when it is set to 12fps, however there is still something strange going on, because in my testing in the SAME lighting/contrast conditions where the 1Dx set to 10fps or slower in AI-SERVO fails completely (meaning not slow focus, but can't focus at all), my older 5D2, 5D, and 7D in AI-SERVO mode all focus lock and track just fine.  If my 1Dx set to 10fps or slower focused in AI-SERVO as well as those older cameras then I would be totally okay with this and move on, but as it stand that is not the case.

I think you are right in that there must be some sort of engineering tradeoff going on here, but why is it that in the same light that the 1Dx (at 10fps or slower) totally fails, the older cameras focus and track just fine?  This is what I would like for Canon to either explain or fix if possible.

Otherwise, I agree with you that this is the finest camera I have ever owned.

Hello Viggo,

I believe the reason the 5D, 5DII, and 7D acquired focus lock on the low contrast, low light, "stationary" towel in AI Servo was because they have a slower frame rate (the 7D lowers its frame rate automatically in low light) which seems to put the emphasis on focus acquisition.  The 7D, MKIV, 1DX also have the default feature for first Image focus priority, which also places an emphasis on slower focusing, as opposed to shutter release. We're not yet saying that the 1DX doesn't track well in AI Servo, we're just saying that the first focus lock of a stationary or slow moving subject in low light, low contrast situations is difficult to lock-on when higher than 10fps are in use.

I think that was Richard Lane's answer to me  you quoted  ;)
1dx, 24-70 L II, 50 Art, 200 f2.0 L

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #74 on: August 02, 2012, 01:36:31 PM »