Quick AF point question

Merlin5

Merlin5

Merlin5

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Joined
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Finchley, London
I had a go yesterday at trying to track moving cars to get that streaky background and sharp focus on the car. Quite tricky! I got a couple of shots that were close to being right using shutter speeds around f30 to f50. I made a mistake though of being in single shot mode instead of AI Servo. And I probably should be in shutter priority mode instead of manual. Anyway, on the 5D mk2, once I focus on a moving target, the red focus point light comes on and goes immediately off. My question is, as I start panning across, can I just rely on any of the 9 focal points to keep tracking the target and keeping it in focus, as long as I keep the target within any of the 9 focal points? Once the green light comes on in the viewfinder after the initial focusing, i can assume it's still focusing as I pan around as long as the green light stays on?
 
First, f is rhe measure of aperture, not shutter speed so there is not f30 or f50. I think you mean 1/30th of a second.

Second, to track moving object, its one of the hardest for a camera to do, especially when its coming towards you. The ideal way to do it is ai servo with one of the back button to focus with your thumb so you hold it down and take a photo with your index finger when want.
 
Yes, sorry, I did indeed mean 1/30th to 1/50th! My f-stop was f13.
When you say use one of the back buttons to focus, do you mean to change the focal points on the fly while I hold the shutter button halfway? Doesn't the 9 point automatic selection do that for me (in AI Servo), change the focal point by itself to keep track?
 
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F13?

Everything is in focus at f13, I would go much wider normally for separation.

As for back button focus, by default the shutter button focus at half press and photo at full press. You can assign the half press to the back button. The reason you do that is you can focus and shoot at the same time.
 
Ok, I'll look in the manual how to assign the back button for focusing.
These are three shots I took at F13, 1/50sec, ISO 640. The background had the sort off streaky out of focus effect I want. Didn't really nail the focus on the cars though. My location wasn't good, there were hanging branches in my view, but I just wanted to quickly test how close I could get to doing this. Needs lots of practise! Should be better next time on AI Servo.

https://i.postimg.cc/DfjZxhv7/Car-1.jpg
https://i.postimg.cc/VNxTfdWz/Car-2.jpg
https://i.postimg.cc/hjVYfc2T/Car-3.jpg
 
Couple of tips:

Watch a couple of YouTube videos on back button focus. I don't mean that in a bad way but it's much easier to understand than me (or anyone else) trying to explain on here. It's a game changer and one of the first things someone should learn IMO.

As mentioned above what you are attempting is panning. In my experience you want to shoot with your f stop wide open, or as wide as practicably possible - this will allow for a nice out of focus background.

You don't want to shoot at any shutter speed higher than 1/125. If you shoot any faster you'll end up freezing the background and not getting that motion blur effect.

Camera in AI servo. On Canon cameras you will no longer get the red illumination or the beep (if enabled). It can be unnerving at first not getting that visual confirmation of hitting focus but you get used to it.

People will operate focus how they feel works best for them. I will select a single af point and keep the moving object within that square. Oftentimes that's easier said than done but it will come with practice.

Camera in burst mode (this is high speed shooting mode) and fire continuously!

Don't worry too much about ISO. As I've said, make sure your shutter speed is in the region of 1/60 to 1/125 and aperture as wide as you can. This will depend on your lens but around f4 should be good.
Just use the ISO to balance the shutter speed. If you are still over exposing with ISO at 100 and shutter speed in that region then increase the f stop as required.
 
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Thanks Gmac11, excellent tips, much appreciated! Yes, no A/V alerts on focus in AI Servo will make me think I don't have focus. I'll have to trust it. I'll go and look up back button focus on youtube. That'll be my next thing to watch. I had previously seen a video about panning to capture cars in motion and these are screenshots from the video which is why I thought I should use a smaller aperture.

https://i.postimg.cc/CK1Q09BH/1.jpg
https://i.postimg.cc/pd61LkKN/2.jpg
https://i.postimg.cc/76JtG7N5/3.jpg
https://i.postimg.cc/SR0TWsZD/4.jpg

I used my 70-300mm f4 to 5.6 lens at 70mm. I'll try with f4 then.
 
Not sure if you can do it in the mk2 but with the mk4 I had this set up

1 - main shutter button can focus and take photo and I have it in single shot focus

2 - assign back button focus to the back button but it triggers AI servo with it

so without adjusting anything I have both at my finger tips.
 
Sorry I should have been a bit more forthcoming about the fstop. I was looking through some F1 photos I got from the last GP I attended and I see they range from f6.3 to f11. However I think the reason for going up to f11 was to keep the shutter speed down. It was in Austria and the sun was blazing. Here in the good old UK we generally don't have that issue (well I certainly don't in NI!).

Below are two examples of a 1/60(f11) shutter speed and a 1/2000(f6.3):

https://i.postimg.cc/JzrM3NbL/IMG-1075.jpg
https://i.postimg.cc/Vkx4QRDy/IMG-1083.jpg

This is an example from an Auto Test day I shot:
https://i.postimg.cc/MGRnN0rF/IMG-7252.jpg

This was at 1/125(f7.1) but again on an uncharacteristically sunny day.

Just to clarify what I had said before as when I read it back it didn't seem like great advice. I maintain the fstop should be as wide as you can get it however as I've since discovered after looking through my back catalogue you may find that 'as wide as possible' could still be as high as f11. It will all depend on the light levels.

Also please don't read much into my composition on these photos - they were taken straight from the unedited RAW files :p
 
The 5d2 focus system is not great at moving subject focus locks. My first few track days were using that and a Sigma 70-200 f2.8 and my hit rate was poor. Also from the test shots you have a lot of tree in the foreground which can knock off the focus with the 5d2 if panning, it doesn't have the options to adjust the focus behaviour like the newer models have.

If you know where the car will be when you want to take your shot you could practice by setting up back button focusing, fixing your focus point where you expect the car to be when taking your shot then ignoring focusing completely and concentrate on your panning technique and seeing how shutter speed and f-stop affects the final image (or switch the lens to manual focus to avoid knocking the focus button by accident). When I've been on circuits where I have to be behind catch fencing I usually fix my focus point first as sometimes this can cause the focus point to jump back to the fence if the camera thinks a fence is more interesting than a car.
 
Cheers Steeps. I set up back button focus last night to my AF-ON button. I like it! It focuses still subjects with one press and then I can let go of the button or I hold it down for continuous focusing when panning. Where you mentioned fixing my focus point where I expect the car to be, do you mean I should let go of the back button?
 
Merlin5 said:
Very nice GMac11! Was that last weekend's Austria race?
Click to expand...
Oh how I wish it was! That was 2017. I had planned to get to the Dutch GP this year but the less said about that the better :(
Yes as Raymond Lin has pointed out above, you also need to delink focus from the shutter button if you are moving it to another button otherwise it defeats the purpose completely.
I made use of one of the custom settings to quickly go back to 'regular' focus when it's required - and believe it or not it can be!
When I'm shooting fast sports such as football and rugby I actually prefer the standard focus method. If using back button focus I'm holding the camera with the back button held in continuously so the AI Servo can track the subject and that's get very tiring on the old thumb after 90 mins!
 
Guys, yeah, my focus is delinked from the shutter button. I went into custom settings and enabled Metering start/Meter+ AF start which gave me the back button focus. Works well.

I also tested it in liveview but it's odd. If I press the back button in liveview, it activates the shutter for some reason, but without taking a photo, and I don't think it focuses.
 
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