5d MARK IV - AI Servo

[midnattsol]

I must say I am a bit confused.  I shot a burlesque show last night, fairly low light but not too bad.  Took my 5d mark iv as my main camera and my 7d mark ii as a second camera for backstage flash shots. I was shooting manual, 500/2.8 on AI servo and the motor drive on high. I set my ISO to auto.  These shows are a lot of movement so need AI to keep up, almost like a sporting event. My iso was bouncing between 1000-8000 depending on lighting but no problem for a 5d.  After the first performer, I checked some of my shots and my miss rate on focus was TERRIBLE.  The focus dot was right on the target but 80% of the pics were not sharp.  I switched off of focus 4 and back to 1 to see if that would help with the same results. The performer was not moving in many of the shots but made no difference so it is not a shutter speed issue. I switched to my 7d II with the EXACT same settings and my hit rate went to 90%. I am under the impression that they have the same focus systems so I am totally confused.  I did have something like this happen last year so I sent the 5d to Canon, they said there was nothing wrong with the camera and recalibrated it.  I am looking for suggestions or feedback, the 5d was way too expensive for these kind of results.  The camera works perfectly in single shot focus. 

[TCampbell]

Just be aware that both One Shot and AI Focus have side-effects.

In "One Shot" the camera uses "Focus Priority"

In "AI Focus" the camera uses "Release Priority"

These priorities control how the camera behaves when you fully press the shutter button.

In "Focus Priority" the camera wont take a shot unless it can lock focus on at least one available AF point (often when people shoot in poor lighting and think the camera is broken because it wont take a shot... it's really because it couldn't lock focus in the available lighting.)

In "Release Priority" the camera prioritizes taking the shot WHEN you press the shutter button as being more important than having focus.  The theory here is that you would have been continuously focusing by half-pressing the shutter button or using the back-button AF-ON to maintain focus ... so when you actually do press the shutter, it will take the shot.  But if you simply press the shutter button (without waiting for it to focus) then it will capture a pile of blurry shots... because that's what it's supposed to do when release priority is enabled.

On a 5D III or IV you can tweak this capability somewhat ... but telling it to put more a little more priority on focus.  

Go into the menu, scroll to the 2nd AF magenta AF tab.  You should see:

AI Servo 1st Image priority

AI Servo 2nd image priority

1st image has 3 possible choices ... "release", "focus" or you can set it in the middle and it will try to balance.

2nd image has 5 possible choices ... speed through focus.

Check your 7D II ... if you are using your 5D IV in poor lighting, you may just not be giving it enough time and need to push the AF tuning a bit farther over to the "focus" priority side.

[midnattsol]

great, I will take a look and maybe adjust a bit.  I shoot a lot of sports so I have used nothing but back button focus for years. I could never go back. 

[amfoto1]

Hi,

I don't have a 5D MarkIV... but I do use a pair of 7D Mark II a lot for sports/action shooting.... AI Servo, Back Button Focus, etc. 

First, were you really using a 500mm f/2.8 lens? That must be massive! (I've got a 500mm f/4 and it's 8 lb. with a 130mm diameter front element!)

I suspect that's a typo, would be interested in knowing exactly what lens you were using, because AF performance is influenced strongly both by the camera and by the lens (and, for that mattter, the user).

Though it's no slouch (much improved over earlier 5D models), the 5DIV's AF system definitely is not the same as the 7DII's. The 5DIV has 61-point AF, 41 of which are cross type and all of which are "f/8 capable", while the 7DII uses a 65-point AF system, all of which are cross-type, but only the center point "f/8 capable". The 7DII's AF is highly optimized for action photography and AI Servo tracking. I don't know if the same can be said of the 5D-series cameras.

7DII (and original 7D) uses a discrete chip dedicated to running the AF, along with dual Digic 6 procesors to handle the images. This is similar to 1D series cameras... dual processors and a separate chip running AF.

AFAIK, the 5DIV only uses a single Digic 6+ processor for everything. (5DS use dual processors for everythng, primarily because of the very large image filles the 50MP camera generates.) This might explain the difference you saw, along with different lenses you were using on each camera.

By the way, it's probably unrelated to the focus issues, but... No, you actually weren't shooting manual exposure. When you use M with Auto ISO, that's another form of auto exposure that in various ways (such as Exposure Compensation) needs to be treated much the same as Tv, Av or P.

 I can't help but wonder if it might partly be less familiarity with teh 5DIV's AF system... at least using it under this sort of circumstance with challenging lighting conditions and AI Servo.  It probably needs to be set up differently than 7DII. Also I don't use the Focus ""Case" presets like you were using, so can't really comment. I'd really like to hear from some other 5DIV users, how they set up their camera for active subjects.... as well as what lenses you were using on the cameras. 

For example, there's a setting on the 7DII which prioritizes shutter release versus AF accuracy. I set it high toward the latter, since missed focus images are of little use to me (someone like a photojournalist might set the exact opposite). I don't know if the 5DIV has that. Even if it does and it's the same, if you have it dialed one way for one camera and the opposite for the other, you would get very different results.

I also tend to use a single AF point much of the time. That's more work for me, keeping the AF point right where I want the camera and lens to maintain focus, but reduces chance of the AF being distracted by something in the foreground or background. I'll occasionally use Expansion or Zone multi-point AF patterns, but usually only when there's little chance of distraction.... the subject is pretty well isolated and the background very plain and distant. There also are adjustments on 7DII that govern how quickly the AF will jump to a different object, such as when a subject passes behind something.

Finally, for action photography I make a point of using USM lenses for their fast focus performance. f/2.8 and larger aperture lenses are the quickest (allow some AF points to perform at a higher level), but f/4 and variable aperture lenses as small as f/5.6 can do pretty well, depending upon ambient lighting conditions.  Whenever there's sufficient lighting, I also stop the lenses down a bit, for a little more depth of field so that even if there are slight focus errors, I'll still get usable images. (You're probably aware, stopping down doesn't effect AF speed and performance, since the lens is maintained wide open until the instant of exposure.)

Again, I'd really like to know what lenses you were using and to hear how other folks set up their 5DIVs.

EDIT: AI Focus is another thing entirely. I never use it and didn't think you were using it either. AI Focus isnt't really a focus mode at all. It's automation that's supposed to determine for you whether the subject is moving, then switch to using the correct mode: AI Servo for moving subjects and One Shot for stationary. If you were using AI Focus, that might explain some of the missed focus. I haven't used it in many years and maybe it's better now... but on older cameras I found it caused a slight delay, slowing AF performance.... and that it sometimes didn't choose correctly or didn't switch when a subject started or stopped moving. After experimenting with AI Focus for a while, I stopped using it and immediately saw a big improvement in my in-focus percentages. IMO, AI Focus is sort of a "point n shoot"/snapshooter mode... much like "Auto". If you were using AI Focus, that could well explain what happened.

Reading the rest of Tim Campbell's response... re: Release versus Focus Priority.... That's what I was trying to describe earlier (and maybe didn't do very well)! It's essentially the same thing on 7DII. FYI: 1st image priority is exactly what it sounds like... governs whether or not the camera should wait (if necessary) for focus to be achieved for a single image or the 1st image in a burst. 2nd image priority governs how the 2nd and all subsequent images in a burst are handled.... whether or not the camera should slow frame rate and/or delay shutter release, if necessary, waiting for focus to be acheived for each image. Again, I set the priority to focus... and just live with any delays (I only very rarely notice any delay).

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2) some other cameras, various lenses & accessories
FLICKR & ZENFOLIO 

[midnattsol]

yes, sorry about that.  I was using a 70-200 2.8, back button focus with a shutter speed of 500 @2.8.  My bad for not being clear. I understand that its not all manual when in auto ISO but that is needed since the subject moves around in different lighting almost the whole time.  I had to adjust my Ex Comp down a 1/3 of a stop to get good results.  I was using single point but in hindsight, I wish I had done the 4 center points like I do when I shoot football.  I did move to 3.2 and 3.5 to get a bit more depth since the iso was not getting out of hand but had to drop the shutter speed to 250. I will try adjusting the priority focus settings to see if it helps.