Autofocus problems - is it the kit or me?

theheyes

theheyes

theheyes

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I shot a couple of sports days this week and it’s the first time I’ve ever done anything with a lot of action going on and was wondering whether the amount of photos I had to bin due to being out of focus was normal or not. I stuck to one lens all day each day and everything was on the 500D.

The first day I used the 50mm f/1.8 mk2 and took around 150 shots, roughly 50 of which I got rid of due to being out of focus.

The second day I took around 300 with the Tamron 17-50 and ended up binning more than half for focus reasons.

Over the two days I got 60 keepers for day one and 70 keepers for day two (the rest were binned due to other reasons), all of which I was very pleased with and I captured some great photos, but I was just a bit concerned I couldn’t nail it with more than a 50% success rate for anything that involved a bit of motion. I wasn’t being paid for the work so it didn’t matter if I missed anything important but it got me wondering if there was anything I could do to improve.

I kept the aperture on both lenses set to f/4.0 as I figured this would allow me a bit more depth of field and not exacerbate any missed focus. Would you say this is sensible or would you narrow the aperture even further?

For those that don’t know, the 500D has a 9-point AF system. I tend to use the centre AF point only 90% of the time as I find it more convenient but for tracking runners I switched it to automatic i.e. using all AF points as I thought this would be the more logical option. Set to AI SERVO mode of course and continuous shooting while panning from the side lines. Through the viewfinder I was doing a pretty decent job of keeping the subject covered by AF points (as far as I could tell) but out of maybe 7 or 8 burst shots the vast majority would be back focused and I felt there was too much of an element of luck involved.

I suppose my question is – is it me, the kit or is it normal? I’m not going to be the one who is quick to blame the hardware, but am I reaching the limits of what are admittedly is a budget camera body and lenses and would a 60D or 7D with better AF and more FPS have made a big difference in this regard? Or is it just my technique and camera settings and I just need more practice?

Thanks for reading - any insight much appreciated.
 
The 50 mkII isn't the greatest when it comes to tracking via Servo AF and I imagine the Tamron isn't going to be much better either (vould be wrong!) (I've only owned the Canon 50mm) but a lens with a better AF system (Canon USM, Sigma HSM etc) could possibly yield better results when in AI Servo I suppose.

I have never used the 550D but my 40D also has a 9 point AF system and it doesn't have any problem tracking movement although I almost exclusively shoot with the centre AF point selected or a single AF point around the centre.

I would suggest testing by only using the centre AF to track your subject via AI Servo, if you still get that must hit and miss then it's either the lenses or the camera's AF system not fast enough to keep up, you could test the latter by panning with a slower moving subject perhaps?
 
I use single point AF for action shots, mainly because then the camera will focus where i want it to, and not where the camera thinks it should be.

Using servo focus and burst mode, you're still always going to get some out of focus shots, so I wouldn't worry too much.

Don't forget though that a blurred photograph can be blurred for a number of reasons, only one of them being down to AF.

In your scenario, you've got subject movement, camera movement, camera choosing focus points (you had automatic focus point selection turned on?), as well as lots of other variables.

As you've found, it's not an exact science, but I wouldn't worry unduly about your kit.

Practice makes perfect, find what works for you (in this case, I think one focus point or you controlling the focus point via switching) and then stick with it.

But, I'd be pretty happy with that amount of keepers, and at least you got your shots.
 
And you're totally sure that it's mis-focused instead of motion blur? Shooting at f/4 on a 500D, you'll need some pretty good light to avoid it... I only say because it could be an easy fix; if it's a focus problem your only option is to try servo for everything or upgrade the body, or use another lens with quicker focusing.

Using centre focus, it's possible that you're focusing, then in the time between between focus lock being achieved and the shutter being fired, your subject is running forward out of focus?
 
got an example with EXIF data you can post?

but generally the way i shoot sport is:

*camera in aperture priority and set to value to cover subject with DOF
*AI SERVO
*center point AF
*switch focus activation to the AF-ON or * button (depending on what you body has)
*adjust ISO to get the shutter speed to the required level

also another thing to concider, how far from the action were you? F4 at 3m only has a depth of field of 50cm.. http://www.dofmaster.com/dofjs.html
 
Ok some interesting replies. Unfortunately I can't post the photos - it's a bit of a grey area/red tape thing with my employer which is annoying so sorry about that.

It seems as though most people use the centre focus point, which I will definitely try in future. Also it's definitely a focus thing as I was keeping the shutter speeds well above 1/1000 to stop the action so camera shake and motion blur shouldn't factor into it. It was a sunny day but I bumped the ISO up a little because freezing the action was the look I was going for, save for a few exceptions panning at 1/50 which came out really well.

Interesting about the DOF being narrow at 3m as I was literally on the sidelines so the distance would have been of that order. I might experiment a bit with narrower apertures.

And yes, I know the lenses I used aren't renouned for their focusing. I do have a 70-200 L so next time I might try that as well. I am thinking of buying another prime though since I love the 50mm 1.8, maybe an 85mm 1.8 or the 100mm 2.8 macro - both have USM so might fare a bit better than the 50.

Thanks for the help, definitely some food for thought.
 
neil_g said:
got an example with EXIF data you can post?

but generally the way i shoot sport is:

*camera in aperture priority and set to value to cover subject with DOF
*AI SERVO
*center point AF
*switch focus activation to the AF-ON or * button (depending on what you body has)
*adjust ISO to get the shutter speed to the required level
Click to expand...

Oh also, could you explain to me what this setting is? Not sure whether it's something I've missed, goes by a different name or isn't on my body. Thanks.
 
Does your camera have a button on the back called AF-ON ?

If not then the mode referred to probably doesn't exist on the 500D. I know it does on my 40D and my 5D2 but that doesn't really help !

Yes - the 7D would be a lot better at tracking the movement as it has just about the most advanced AF system of any Canon SLR at the moment.
 
basically it moves the focus activation to the AF-ON or * button (depending on what your body has). it also splits out the focus from the exposure. quite a long but interesting read here - http://www.talkphotography.co.uk/forums/showthread.php?t=303465

Hodders said:
Does your camera have a button on the back called AF-ON ?

If not then the mode referred to probably doesn't exist on the 500D. I know it does on my 40D and my 5D2 but that doesn't really help !

Yes - the 7D would be a lot better at tracking the movement as it has just about the most advanced AF system of any Canon SLR at the moment.
Click to expand...

if the AF-ON button doesnt exist on the 500D then you can set it to use the * button instead.
 
the 5d mk2 AF is no better then my 400d. maybe slightly better but not great at all. 7d has a far superior AF then the 5d.

Also, the tamron lens u have and i have is not great at AF either
 
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