AI Servo tips, or focusing on walking subjects on 5Ds and 70D

[randomuser74]

I have some older equipment, but it should be fine for this low-key backyard wedding I'm shooting. Canon 70D and 5Ds both are misfocusing in AI Servo mode when doing mock trials of walking-down-the-aisle shots. In One Shot mode with still subjects, things look sharp, so I know it's not a lens calibration/micro-focus adjustment issue. I have a Canon EF24-105mm F4 L IS USM lens, and the minimum aperture is 4 so it's not really a narrow focal plane problem. Shutter speed is 1/250 minimum, but mostly much higher. I use a single AF point and place it directly on the subject's face and try to keep it locked on as they walk. Zone AF points didn't seem to work as well. I'm back-button focusing, holding down the AF-ON button continuously and trying to fire off 8-10 shots. Most are pretty soft and not as sharp as One Shot, and some are downright blurry. I've tried Live View, but the lag is so terrible that I only get 1 or 2 shots and the walk is done, and those are blurry as well. These cameras don't have eye tracking. I've done a handful of weddings with older DSLRs and film cameras and never really had this issue, or maybe resolution was just too low to notice. Honestly, my phone camera does a better job for this one scenario! There must be some technique I'm missing. What other tips can I try or is there some setting holding me back?  I have it set to focus priority.

[wq9nsc]

The single point on their face may not have enough info to work with all of the time so you may want to change your selection to either single point with expansion to add the additional 4 points in a plus sign pattern around the single point or even choose single point with expansion which adds the 8 points surrounding the single point.  The single point is still the preferred point for the AF system but it allows it to expand to the other selected points when it needs to do so.

I have never been a fan of back-button focus because I shoot sports with at least two bodies and often switch during the middle of a play so I have to minimize the time lost during switching and having to use a separate AF button is not in the cards.  Your camera should have no issue following a slow walk down the aisle, if you like BBF then continue to use it but AF coupled with the shutter release should be fine.  I reprogram the AF button as an AF stop button on my 1DX series camera bodies for the rare occasion when I want to freeze focus and recompose and I am not using a "great white" lens with its own array of AF stop buttons.  

I have never used a 70D but I have a 5DS body and these have 6 AF "cases" to match the AF system to the event. It is hard to imagine a camera having an issue following a slow steady walk but you could experiment with the different AF cases with your 5DS to see if one works better but I would think the default Case 1 would be fine.

Rodger 

[p4pictures]

On both these cameras there is a focus mode called AI Focus as well as one-shot and AI Servo. Please make sure you are NOT using AI Focus as this mode, in my experience, is largely unreliable. 

I agree with Rodger, the AF point with expansion is a good choice for the EOS 5Ds, as initially the camera focuses using the central point in the group, and once in focus the other points can be used by the camera if needed. AF case set to 1 is suitable for this slow movement. An alternative is to use the whole group of 45 points and enable an initial point for servo AF in AF4 Initial AF pt AI Servo AF. This means that you have an initial AF point to aim at the subject, but the camera can use the other 61 points to track the subject if they move away from that initial AF point. You should also look at the settings in the AF2 menu for servo 1st image and 2nd image priority and set these to Focus priority. Lastly I would ensure that Auto AF point selection: EOS iTR AF is enabled. This works with the 61-point AF mode to more accurately track faces. 

The EOS 70D lacks the AF point with expansion, so I would use 1-point or Zone AF. 

Please check the images on your camera in playback mode and turn on the display of the AF points. If there are no AF points shown then it means you lifted off the back button while shooting so the camera was not focusing at the time the photo was taken. If you see that problem, then I would also advise focusing with the shutter button not the back button. 

[pcs1]

Your description of soft and blurry sounds to me more like movement/to slow shutter speed, focus problems would lead to missed(front/back)focus. Maybe you could post an example?

[randomuser74]

Thanks, everyone!

These are helpful tips.  I don't have a picture to post because they are all of my spouse and children and I don't want those out there on the internet.

I have a clarification for p4pictures.  With the method where I enable the 61-point focus but have an initial AF point in Servo, it seems like the only option is for that point to be at the center.  For the walking shots I want these to be vertical with the selected point higher up where the faces would be.  I'm not able to figure out how to get that center point to move.

Also just a general clarification: As long as nobody is moving forward or backward out of the plane of focus, slight movement is okay in One Shot, is that correct?  If so, I just need to get through these walking moments and then everything else during the ceremony could be shot in that with viewfinder or even Live View for the best focus.

[ebiggs1]

" I don't have a picture to post because they are all of my spouse and children and I don't want those out there on the internet."

It's easy to blur faces beyond recognition with Photoshop or some other (DPP4) editor. Samples will really help find a solution.

I've been a wedding shooter for many decades and I can confidently say I never used or use any Ai-servo, AF assist mode. Always, One Shot and then only the center focus point. Ai-servo or AF assist is just not necessary. The very best advice I can give you if you want to really be good at weddings is, keep it as simple and as least complicated as you possibly can. Always have two of everything. And many memory cards which you should change out often.

Here's the point you want to make sure what you want in focus is what you want in focus. Do not let the camera decide what you want in focus or what to focus on.

[stevet1]

randomuser74,

I'd like to eliminate camera shake as a possible cause.

Are you using a tripod, or are you hand holding?

Steve Thomas

[randomuser74]

stevet1, it might be camera shake.  It's hand held, but I'm trying to keep as still as possible. I don't have the IS enabled on this lens because I just find it annoying.  But maybe those two things are solutions.

Here's an image.  The face is of course the most important thing to look at, but I've blocked that out.  The hair and ears give a good indication of the blur level of the face.  Hopefully you can zoom in to see that.  

67 mm, f4, 1/400

[p4pictures]

Image stabilisation only corrects the camera movement, not the subject, your choice about using it, but it would stabilise the background of the scene. At 1/400th I would expect the subject to be sharp enough if they are walking at regular pace, though the hands have a slight blur to them. 

[randomuser74]

Thanks, p4pictures.  Yes, there is a slight blur and softness to everything that is just confusing.  It only occurs with moving subjects in servo.  Did you see my question to you above about the 61-point with initial AF point suggestion you gave?