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Author Topic: 1DX - Ai Servo Issue - Low light focus failure! Final Update 05/09/12  (Read 33491 times)

Richard Lane

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #75 on: August 02, 2012, 02:15:50 PM »
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.


Excellent questions and I wont pretend to have all of the answers. Perhaps Canon has made a trade-off for AI Servo tracking motion sensitivity compared to stationary subjects, in low light, low contrast. I don't think that this is actually anything new as my MKIV behaves the same as the 1DX.  When I locked in with the 7D in AI Servo, it did take a couple of seconds and it was not nearly as fast as initial One Shot focus lock. So even if it does this one thing better, the MKIV and 1DX are so much better.  If I moved the camera around a bit on the target, acquistion was a little faster.

I have never had any trouble auto-focsuing with the MKIV at sports venues, and the MKIV performed exactly the same as the 1DX when I did the low contrast tests. Now in better light the 1DX focuses faster than the MKIV.  Look, you could own a Ferrrari and if you're driving it in the rain, and at night, then you will need to keep your foot lighter on the pedal.  However, with some dry roads and daylight then you'll be in heaven.

Canon states in their Manual that in low contrast, and low light you may need to use Manual focus, which sounds ridiculous. 

For initial focus acquisiton, other tehniques would include, grabbing the edge of the uniform, helmet, transition from jersey top to pants, alternating from one player to another, switch from  background to foreground, pump the One Shot button, lower the FPS, change to release priority and then wait for the player to move a certain distance which definitely aides AI Servo in tracking mode, you can also turn the manual focus dial. Now, I don't actually regularly use these techniques, but they are all available to us.  I also do not use all AF points selected, unless I'm shooting into a clear sky.  I usually use manual single point AF with expansion points, so I put that point right near an edge if need be, but like I mentioned earlier I haven't found it to be even noticable in real world shooting  situations, however that does not imply that some cameras may be having some difficulties.

My friend has a 1DMKIII and he shoots Surfing in One Shot Continuous High speed shooting, because he says that its better than his AI Servo mode.

I think we are all going to have a slight learning curve with all of these new settings, and I can't wait to play around with the new AF Cases and tracking acceleration and deceleration sensitivites in the new AF menus.  I haven't had a chance to experiment with this yet, maybe it will help. 

If Canon can improve on this with a firmeware update then I would be thrilled.

Rich
« Last Edit: August 02, 2012, 04:09:50 PM by Richard Lane »

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #76 on: August 02, 2012, 08:04:27 PM »
Hi Guys:

I did notice something the other day - hopefully someone with more experience can tell me if this may possibly be why we have the issue

Metering Range EV 0 - EV 20 (at 73°F/23°C with 50mm f/1.4 lens, ISO 100)
The Canon 1Dx offers a 61-point autofocus system, with autofocus sensitivity from EV -2 to 20 at ISO 100 with an f/1.4 lens.

I'm on the working assumption that the meter tries to see the object prior to af acquisition - but if the meter is 2EV above the AF - it's not going to see what the AF can see?

Or am I way off the mark?

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #77 on: August 02, 2012, 10:44:24 PM »
I wondered about that, and if disabling iTR (which depends on the metering sensor) would help?  But I'm not sure how the change with frame rate would play into that hypothesis...
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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #78 on: August 02, 2012, 10:47:15 PM »
I wondered about that, and if disabling iTR (which depends on the metering sensor) would help?  But I'm not sure how the change with frame rate would play into that hypothesis...

On my day 3 tested I did turn off iTr to see if it played into but seemed to do very little in terms of helping the situation - may rerun a few test at L 3fps and itr on/off in that basic 60w room setup rather then original -1 to 0 ev lowlight
« Last Edit: August 02, 2012, 10:54:38 PM by Sycotek »

Peter Dawson

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #79 on: August 03, 2012, 01:28:27 AM »
Last night I finally got a chance to test the AF in low light.  I shot a little tennis action with very poor flood lights.  70-200mm 1/1000s, F2.8, ISO12800.  IMO this is pretty poor lighting and the AF was incredible.  I did not notice any difference when using 12FPS or < 10FPS (I also tried the zone AF, which I never trusted much on the 7D, and it was amazing how the points danced around the players torsos - I was grinning ear to ear).  So in a nut shell, I'm very stoked with the AF performance.

I then decided to try and reproduce the H speed AI AF issue, and sure as nuts, in lower lighting situations the 12FPS AI AF just racked the lens back and forth.  Switch to 10FPS and locks first time.  I got home and tried the 5D II and it also locks first time.  This was by no means an extensive test and I did not try and find that exact lighting point where the 12FPS falls apart, but as a reference 70-200, F2.8, 1/80, ISO25600.

So thats +1 with a low light AF gremlin :(  (not that I'll ever shoot in these conditions in AI AF, but still . . .  .)
« Last Edit: August 04, 2012, 12:52:55 AM by Peter Dawson »

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #80 on: August 03, 2012, 03:24:43 AM »
Last night I finally got a chance to test the AF in low light.  I shot a little tennis action with very poor flood lights.  70-200mm 1/1000s, F2.8, ISO12800.  IMO this is pretty poor lighting and the AF was incredible.  I did not notice any difference when using 12FPS or < 10FPS (I also tried the zone AF, which I never trusted much on the 7D, and it was amazing how the points danced around the players torsos - I was grinning ear to ear).  So in a nut shell, I'm very stoked with the AF performance.

I then decided to try and reproduce the H speed AI AF issue, and sure as nuts, in lower lighting situations the 12FPS AI AF just racked the lens back and forth.  Switch to 10FPS and locks first time.  I got home and tried the 5D II and it also locks first time.  This was by no means an extensive test and I did not try and find that exact lighting point where the 12FPS falls apart, but as a reference 70-200, F2.8, 1/80, ISO25800.

So thats +1 with a low light AF gremlin :(  (not that I'll ever shoot in these conditions in AI AF, but still . . .  .)

Any thoughts about the metering being 0-20ev and the af being -2ev-20ev ? I can' recall where I read the dx constantly meters the scene in servo which could be a reason?

Peter Dawson

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #81 on: August 03, 2012, 03:52:13 AM »
I had actually not realized the metering range differed to the AF range until reading it this morning.  I never did quite understand why the 7D's frame rate dropped to 4FPS when the lighting was poor, even when in MF.  Maybe this is a similar scenario?  Along similar lines then, if you disable iTR, use a WB mode other than AWB and manual exposure mode, then are you essentially negating the need metering, in which case eliminating the metering range from the scenario?  Maybe worth a test when i get home from work this afternoon.

as an aside, do you know if there was ever an explanation for the 7D frame rate drop in low light?

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #82 on: August 03, 2012, 04:41:01 AM »
I've noticed the 7D was slower in dark situations. But as some one said above you don't drive a fast car flat out in the rain, or the dark come to that. Is it really reasonable to expect world beating good conditions in poor conditions? I don't think so.

FWIW I never realzised how much of an step up the 1Dx would be compared to the 7D. Not only will it focus better. It produces pictures that can be cropped harder so I don't miss the 1.6 crop on the sensor. It also drives the lenses much faster. I used to turn off the search for focus if AF is not posible feature, there is no need to do this with the 1Dx because it drives the lens so fast its quicker to wait the second or so it takes to run the lens from stop to stop, rather than the 3 seconds the 7D took. All this on top of the breathtaking low light IQ.

BTW Dont think I don't like the 7D. Its a great camera. To go back to the car senario, I like my Volvo and its been great for me, but its not a super car.

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« Last Edit: August 03, 2012, 06:28:27 AM by Skulker »
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Peter Dawson

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #83 on: August 03, 2012, 05:29:28 AM »
I Quite agree Skuller.

I also upgraded from a 7D and the difference is incredible.  The 7D slow FPS caused lots of noise when the camera was released. I dont think there was ever an explanation, nor a fix, but because noone shot in those conditions, the issue went on the back burner.

Just for the record, I have yet to experience the Err 80 issue with my camera.  I have never used the orientation linked AF points function and that menu item is still set to the default "same for both orientations" option.

Quick question.  Do you normally turn the camera off prior to changing lenses or just change them.  I never turn the camera off before changing lenses.  Is this wrong?
« Last Edit: August 03, 2012, 07:36:53 AM by Peter Dawson »

Sh1n1ng Forc3

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #84 on: August 03, 2012, 01:22:18 PM »
I had actually not realized the metering range differed to the AF range until reading it this morning.  I never did quite understand why the 7D's frame rate dropped to 4FPS when the lighting was poor, even when in MF.  Maybe this is a similar scenario?  Along similar lines then, if you disable iTR, use a WB mode other than AWB and manual exposure mode, then are you essentially negating the need metering, in which case eliminating the metering range from the scenario?  Maybe worth a test when i get home from work this afternoon.

as an aside, do you know if there was ever an explanation for the 7D frame rate drop in low light?

This is great thinking.  I will test this out as well.  I will do all the metering manually (manual WB, disable iTR full manual mode) and let the camera just worry about AF and see what happens.

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #85 on: August 03, 2012, 01:39:14 PM »
This is great thinking.  I will test this out as well.  I will do all the metering manually (manual WB, disable iTR full manual mode) and let the camera just worry about AF and see what happens.

I predict no difference. I don't believe there's a way to actually turn off metering.  Setting everything to manual means the camera won't actually do anything with the metering information, but it's still going to collect it, and I would bet that if that's the cause of the problem then setting everything to manual will be irrelevant. Worth a try though…
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Richard Lane

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #86 on: August 03, 2012, 01:47:52 PM »
When I did my low light, low contrast tests, I used single point with 4 expansion points.

I would like to reiterate that I don't think this is a low light issue.  It is more of a "low contrast" issue.  When I did my tests I used a low contrast solid color gray towel, in AI Servo @ ISO 25,600 and the 1DMKIV and 1DX had a difficult time locking focus onto the center of the towel.  Then when I focused on the edge of the gray towel, there was no problem focusing at all, even though the light hadn't changed and it was still considered very low light @ 25,600.

Then yesterday I tried a coloroful "high contrast" striped beach towel also @ 25,600 in low light, and the 1DX focus locked on the center of the towel with no problem at all.  Then I tried the gray towel again as a control and the 1DX wouldn't lock onto the center of the low contrast gray towel.  Please note that the light source hadn't changed at all.  So, the issue was more with a "low contrast target" and "not a low light target." 

However, even in low light @25,600 ISO plus low contrast, it was still very easy to overcome any deficiencies by simply aiming for the "edge" of the gray towel whereas there was no focusing issue at all, even in AI Servo at 12fps.

Just for completeness, as soon as any reasonable amount of light was introduced into the scene, the 1DX locked right onto the center of the low contrast gray towel. Also from the other day, One Shot Mode had no problem focusing on the center of the low contrast gray towel even in low light.

I didn't use the All 61 Focus point mode, which would make it nearly impossible to focus on the edge or corner of the low contrast gray towel since the camera doesn't know what I want it to do.

I hope that helps!

As far as changing lenses with the camera on or off, it is probably a good idea to try and change the lens with the camera off, since it has been said that when the camera is on the charged sensor may attract more dust.  So my practice has been, when I'm not in a rush I shut the camera off, and if I'm in the middle of shooting something and I need to change lenses quickly, then I leave the camera on.

Rich

Edited:  I don't think this is a metering issue either. If it were a metering issue or low light issue then why was I able to focus on the "EDGE" of the low contrast gray towel in low light, and why was I able to focus on the "center" of the higher contrast srtiped towel in the same low light?  In my opinion, I wouldn't call any of these test results an issue at all.
« Last Edit: August 03, 2012, 02:40:43 PM by Richard Lane »

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #87 on: August 03, 2012, 08:35:28 PM »
Just a question here, so how is the 1d X af?

How many keepers do you have of a runner, a car speeding towards you, kids running around, birds leaving a branch , simple tasks compared to what Canon says it can..

I remember the D4 gave of 100% tacksharps and honestly would like to hear if it's as good as that... i found the mk4 pretty average for a simple test of a speeding biker, i had to chose the few focused one's and not the right moment. Is it perfect under good light and simple movements?
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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #88 on: August 05, 2012, 12:55:30 AM »
Just a question here, so how is the 1d X af?

How many keepers do you have of a runner, a car speeding towards you, kids running around, birds leaving a branch , simple tasks compared to what Canon says it can..

I remember the D4 gave of 100% tacksharps and honestly would like to hear if it's as good as that... i found the mk4 pretty average for a simple test of a speeding biker, i had to chose the few focused one's and not the right moment. Is it perfect under good light and simple movements?

Hi Mate - in good light, tack sharp nothing dropped, in low light (where i normally shoot and hence the problem) it does drop probably in the realm of 8% and not all images are tack sharp - it is a bit like the lottery in low light at 12 fps.

However at 10fps or lower I haven't seen a frame dropped in similar conditions.

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Re: 1DX - Ai Servo Issue - Low light focus failure! UPDATE 31/07
« Reply #89 on: August 05, 2012, 05:22:52 AM »
Just a question here, so how is the 1d X af?

How many keepers do you have of a runner, a car speeding towards you, kids running around, birds leaving a branch , simple tasks compared to what Canon says it can..

I remember the D4 gave of 100% tacksharps and honestly would like to hear if it's as good as that... i found the mk4 pretty average for a simple test of a speeding biker, i had to chose the few focused one's and not the right moment. Is it perfect under good light and simple movements?



Hi Mate - in good light, tack sharp nothing dropped, in low light (where i normally shoot and hence the problem) it does drop probably in the realm of 8% and not all images are tack sharp - it is a bit like the lottery in low light at 12 fps.

However at 10fps or lower I haven't seen a frame dropped in similar conditions.

Wow, that's awesome to hear, since I'm aware of the 12fps lowlight problem, and counting on a fix from Canon, and i can easily live with 10 fps in lowlight.

Thanks! Seems the 1d X can makes use of the 12 fps, something the mk4 never could at 10...
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