Quick AF point question

Merlin5

Merlin5

Merlin5

Soldato
Joined
17 Aug 2009
Posts
18,395
Location
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?
 
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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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
 
Yes, sorry Raymond, I should have said panning, that was misleading of me. Yes, I'll try lowering the f-stop and ISO. And thanks! Can only get better from here I hope. :)
 
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.
 
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?
 
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.
 
Raymond Lin said:
Huh! It's been so long I clearly forgot.
Click to expand...

I just learned that Liveview has three different autofocus modes all using the AF-ON button to focus, and the shutter sound I was getting in Liveview when pressing the back button/AF-ON was the mirror dropping down in AF quick mode. Don't think I'll bother much with Liveview.
 
Wow, those are great shots SDK! Very well defined cars and bike.

"Don’t forget the shutter speed / focal length rule".

I was using my 70mm to 300m lens at 70mm minimum focal length when I did my panning the other day, so does the rule mean my shutter speed should have been 1/70th? I did have IS on though.
 
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