Gear Talk > EOS Bodies - For Stills
1DX - Ai Servo Issue - Low light focus failure! Final Update 05/09/12
Sycotek:
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Update 05/09/12
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Finally got an answer for this guys: It's a feature...
CPS London via CPS Australia:
"On the first issue of AF tracking in low light. Everything you found was correct and the camera needs to be dropped back to 10fps to AF in the lowest light conditions. At 10fps the camera can focus fast and effectively @ -2 Ev Level but at 12fps the Ev Level is changed to -0.5 Ev. This is because of the light reduction when the mirror moves at that speed. The camera does this automatically. This is what you were experiencing under the conditions of the cat walk. This is comparable to all professional 35mm products out there on the market"
On a side note: does the picture below with the 10 and 12 fps comparison even remotely look like 0ev let alone -2EV ?
Anyway - since I hadn't heard from Canon, chasing it up every day I actually switched over to a D4 setup after a mishap with the 1DX and AF assist (bug 2) at a reception - and haven't been happier - I don't have these limitation anymore. It's less a lottery and more consistent frame to frame shots, low light is substantially better AF and i can actually see what i am focusing on - finally.
Anyways hopefully this will help the PJ's understand what is happening.
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Update 21/08
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Still no word from Canon regarding the findings. However they have replaced the my body - I now have a body starting with SN 05 rather then 04.
So changing nothing but FPS L to 10 FPS I ran a very simple test:
So 2nd unit, brand spanking new and exhibits same issue.
If this body doesn't have a bug with the 70-200 f2.8 II/600EX combo, I'll put up with not being able to use 12fps and hope they fix it via firmware update.
Although a month with no reply is just bad form from Canon.
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Update 31/07
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Replicated issue with a brand new 1DX at the store I bought mine from. It's not isolated as I had hoped - staff can't believe it either.
Waiting on canon now
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Update 29/07
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Issue has been isolated to anything more then 10 fps when shooting in low light - Initial target lock is hindered and at times target subject can not be locked on (lens racks to infinity and stops) - af servo tracking is reduced by 80% in some instances the af tracking stops completely.
And by low light I mean - my testing area is a 60w equivalent cfw room light, 4mx4m room and my girlfriends face (porcelain skin dark eyebrows and dark eyes plenty of contrast). In direct comparison my trusty 7D locks on and tracks without issues.
Setting the servo between 3 and 10 fps fixes the issue on the 1DX
Many thanks to justaphotographer for isolating this issue.
Have reported to Canon - waiting to see a resolution - for now set fps to 10 or less.
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Update 27/07:
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OK so speaking with Canon We have isolated it down to an AF function/modification. It doesn't seem to be a custom function change.
I tend to use case 1 and case 4 and modify case 4 (all sliders moved to the very left) - now I can't seem to figure out what combination of changes make the AF balls up. I had everything set as I like it last night but the second i changed over rotation to computer only (as i tend to shoot portrait mode) the af started to play up. Undoing the rotation change did not fix the issue. Had to reset to a working backup.
If I leave the af setting as stock default everything works properly.
And as it has always been this only shows up in low light Servo.
If anyone is interested I can load a broken config they can play around with and see if they can work it out.
It's a little frustrating as I don't know what I am changing that's causing the AF to bug out. As proved to me when I was shooting with canon in and underground car park the 1DX could lock onto a black car moving at 20+ km/hr in next to no light and get a ridiculously sharp image.
Canon is working on it, as am I - keep keep this updated.
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Ok so for all those not wanting to read everything here is the conclusion:
Sat with Canon Australia Pro Support this afternoon - which they came to my work after My work hours, sat down for a coffee, gave me a few tips and fixed my problem - I really could not ask for more support from any company! And remember they are from a completely different state then I!!!
Anyways after being schooled on some af config case tweaks we took the cameras into an underground carpark probably a good -1 to -2ev at least.
They tested their camera no issue - passed it to me and it blew me way snap bang locked no issues. They grabbed mine and it went ass up - they couldn't believe it.
Went through all the settings and couldn't work out what it is. So we copied the working 1Dx's config on a memory card and loaded it on mine and it's like a brand new camera - it's like night vision tbh.
So yeah if you are having issues as per below - grab this config file: https://dl.dropbox.com/u/33440790/DXSave/WORRKSSS.CSD and load it.
Canon will get back to me as we are unsure if its something funky in the settings or setting screwed up something in servo logic. Either-way I will update this as soon as I am made aware.
Thank You Canon Australia for taking care of Me :)
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Not looking to bag out the DX - actually looking for help from other owners and or Photographers that can explain this phenomenon:
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Issue: Low light Ai Servo mis-focus/no-focus
Full-size images here: https://dl.dropbox.com/u/33440790/weirdservo.zip (65MB)
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1 body – 1DX
3 Lenses – ef50 f1.4, 24-105 F4 L, 70-200 f2.8 II
Shot in Jpeg – all options on (ALO, NR, Lens Correction etc…) and then all options off.
All handheld (no tripod av)
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I’ll preface this with; on the night prior I was out shooting under moonlight – without any notable issues – with, of all lenses - the ef 50 f1.4 (which if you know and love the lens, you know it hunts focus in low light). With my short time with the 1DX , my impressions of the 1DX’s AF is that it snaps to focus on objects You cannot physically see and locks on with near-possessed speed.
Now last night I found this issue when trying to track my cousins head/face moving through the house. It wasn’t particularly dark 3 room lights registered iso 1600-3200 f2.8 can’t remember the shutter speed. She got sick of being target practise so I turned to my dog. The 1DX wouldn’t grab focus either.
By this I mean it racks the lens to infinity and stops or just stops AFTER it’s visibly passes focus. Not and MFD issue either – after a slight mini panic attack, I swapped over lenses and same issue, swapped to the prime and exact same issue. Thought it was the changes I made to case 4 so swapped it to a default case 1 – same issue. I haven’t played around with 1st and 2nd frame preference but I then swapped it to focus preference and still no change.
Intrigued from my experiences the night before I swapped it to [One Shot] and it focused and locked on with possessed speed once again. Swap back to [Ai Servo] and it racks to infinity/racks past.
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So in the original room there were too many variables of people moving through the house changing the light so I setup a pretty average testing area:
This was [One shot] 24-105 at f4@24mm, 1/40, iso 25600
This was [Ai Servo] – same settings. Just failed to focus.
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Shot from the other side of the room:
This was [One shot] 24-105 at f4@105mm, 1/25, iso 25600
This was [Ai Servo] – same settings. Just failed to focus.
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So then I thought let’s bring in 3 times more light (even with the f4/5.6 crosstypes more light can’t be a bad thing)
This was [One shot] EF 50 f1.4 at f1.4@1/40, iso 3200 (bottom af point from memory)
This was [Ai Servo] – same settings. Just failed to focus. (iso 4000)
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So finally I thought it was a contrast issue – so added more contrast:
This was [One shot] EF 50 f1.4 at f2 @1/40, iso 6400
This was [Ai Servo] – same settings. Just failed to focus
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I thought the Servo using ITR then needed more light so turned off ITR and it had the same issue.
I’m out of ideas for explaining this one.
Please note: I shot and tried all AF modes to acquire lock via [Ai Servo]. [One Shot] locked on with any AF mode selected.
robin:
What kind of priority setting do you use? No I don't have the dx, yet, but I had same with 1D Mark4 some time ago..
drjlo:
Well, going by my 5D III AI Servo, I would say AF can be unpredictable, simply missing focus under certain circumstances, often in low light and depending on lens. Then again, at other times that seem "difficult," it has no problem focusing with AI Servo.
As usual, if AF lock is crucial, I use One shot. With 1DX price point, I would have thought it would be much better than 5D III though.
Sycotek:
--- Quote from: drjlo on July 06, 2012, 12:53:35 AM ---Well, going by my 5D III AI Servo, I would say AF can be unpredictable, simply missing focus under certain circumstances, often in low light and depending on lens. Then again, at other times that seem "difficult," it has no problem focusing with AI Servo.
As usual, if AF lock is crucial, I use One shot. With 1DX price point, I would have thought it would be much better than 5D III though.
--- End quote ---
This was just AV mode nothing special.
I'm still waiting on canon's response. I did further testing and seems to crap out on a certain grey point (from my testing) blue or red or white target in the same low light and there was next to no issues
Single shot does lock down to the rated -2ev (tested with a light meter) didn't think at the time to test where the servo craps out at.
Sycotek:
Further testing:
I don’t think the 100K rgb sensor is quite as refined as it should be.
I tested this theory over lunch with a red, blue, brown, grey dark box (so to speak) – focused on the canon black cap using the canon logo as target:
[One Shot] - 1/50 f4 at 105mm iso 25k – found that it is 2-4x faster on [one shot] with iTR on and locked on without issues – I removed iTR just to make sure it wasn’t interfering.
[Ai Servo] - 1/50 f4 at 105mm iso 25k - fails to lock and racks the lens to infinity.
[Ai Servo] 1/80 f4 at 105mm iso 25k - I replaced the black cap with a silver eclipse mint container and it locked on instantly with [One Shot] and [Ai Servo] it also had no issues locking onto red, blue and white either.
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I was having issues one shot - locking on grey objects at -2ev (which is sort of expected) adding in a white and red object made it easier but it still wasn't a cakewalk do to the af points not lighting up and not being able to see where the af point was in correlation to the target. I had to use a tripod and a torch to make sure I had the af point on the object... otherwise i had to keep moving the af point back and forth just to be able to see where the point was...
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