Canon AF options .. why not use AI Focus all the time?

Rupert67

Rupert67

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Canon users will be familiar with the usual autofocus settings, these being One-Shot, AI Servo and AI Focus.

Since AI Focus would seem to offer the best of both worlds (i.e. if the subject starts to move, you can still track it as if you're using AI Servo) why would you not keep your camera permanently set to this mode?
 
Other people with more expertise might correct me, but in my experience it is because on some bodies One-Shot is the most reliable focusing method that maximises the chance of getting the shot in perfect focus. AI Focus may think your subject is starting to move when it isn't, thereby rendering your shot out of focus when One Shot would have nailed it. If you're doing landscape photography you certainly wouldn't want to take any chances with anything else other than One-Shot.
 
Back button focus, AI servo and set the exposure to be measured at shutter release, set that to C1 ( program modes)
BBF , Single Shot , exposure as above and set that to C2.
There really is little point in AI Focus if you use BBF, a single press in AI servo does the same job as AI focus
 
troutfisher said:
Back button focus, AI servo and set the exposure to be measured at shutter release, set that to C1 ( program modes)
BBF , Single Shot , exposure as above and set that to C2.
There really is little point in AI Focus if you use BBF, a single press in AI servo does the same job as AI focus
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I'm sure I haven't a clue what you're talking about troutfisher, but I thank you for the depth of your reply!

It seems that the consensus thus far is to stay with One-Shot AF and only use the others if you're expecting your subject to move towards or away from you. I've already re-set my 5DIII accordingly.
 
DemiLion said:
AI Focus can be pretty unreliable. It's the one focus mode that I'd never use (unless by mistake).
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This.

I've been shooting Canon for 18 years and I spend too much time on Internet forums (including a lot of time on Canon specific ones) and I've never known anyone recommend AI Focus, it's about worst case scenario in most people's opinions.
 
troutfisher said:
Back button focus, AI servo and set the exposure to be measured at shutter release, set that to C1 ( program modes)
BBF , Single Shot , exposure as above and set that to C2.
There really is little point in AI Focus if you use BBF, a single press in AI servo does the same job as AI focus
Click to expand...
Actually, this is quite common.

@Rupert67 it might be worth having a play with back button focus.
 
I think if AI Focus actually worked properly on any Canon, it would be a great option. I'm not sure about the recent cameras, but it most certainly lacks any sort of intelligence, artificial or otherwise on most of them I've tried. :D
 
Yeah as mentioned it's not very reliable.

It's not even been on my last couple of bodies the 1DX and the 1DX2
 
Phil V said:
Actually, this is quite common.

@Rupert67 it might be worth having a play with back button focus.
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artyman said:
As already said set it to Back Button Focus leave it on Servo, a quick dab of the back button and you have one shot, hold and it will track the subject, leave the shutter button to deal with exposure.
Click to expand...

Thanks Both, I'll give it a try.
 
Just to echo what everyone has said, ignore Ai Focus mode stick with Ai Servo and BBF. I also have a 5D3 and use this setting 100% of the time, if I'm shooting moving objects then I'll use the expanded (9 points) settings rather than single point.

Here's a handing PDF on how to use the 5D3's AF settings and the different cases. May be worth a read.
http://cpn.canon-europe.com/files/e...ii/AF_guide_EOS5D_MarkIII_eng_January2013.pdf

and heres a video on why BBF is better
View: https://www.youtube.com/watch?v=8PN9R0D3pF0
 
Rupert67 said:
I'm sure I haven't a clue what you're talking about troutfisher, but I thank you for the depth of your reply!

It seems that the consensus thus far is to stay with One-Shot AF and only use the others if you're expecting your subject to move towards or away from you. I've already re-set my 5DIII accordingly.
Click to expand...

Back button focus and ai servo you will have information on by now..
You can set the camera so it measures the exposure when the shutter is fully depressed to take the photo not the half press as is usual
That combined with ai servo and bbf makes life very easy
This comes into its own if you are tracking something which is moving in and out of shadows so you get the exposure when you take the shot not before.
On the top left hand dial of your camera are marks c1,c2 and c3.
These are programable so instead of having to alter focus method,shutter release etc you program the settings and then switch from one to the other
 
Not sure that the 1DX has even got the Al focus option I will check later
 
5D mk3 has some pretty decent focusing system, but it needs a lot of work and practice to get the best out of AI Focus, but it is useful in some circumstances as an example motorsport with a subject that moves in a predictable way, but I think because Spot AF is easier to use, most people have techniques to get around the issues, so either spot af and refocus (or focus and wait) or AI servo as best of both.
 
Thanks for the tips @troutfisher on the custom settings. I've never really used them before, as I wasnt sure how much info it saved. Anyway I've just set up as following

C1 (Sports) Tv, AI Servo, Expanded (9points), +2/3 EC
C2 (People) Av, Single Shot, Single Point, +2/3 EC
C3 (Flash) Tv, Single Shot, Single Point , -1 2/3 EC

Common across all settings are:
Back Buton Focus
DOF Toggles between Single & AiServo in case of emergency.

1 question though, you mentioned about exposure being measured at release (not half press), where is the option for this. From what I can see on the 5D3, the shutter release can be either, AF & Metering Start / Metering start or AE Lock. Currently it is set to Metering Start is this what you mean?
 
ChrisHeathcote said:
Thanks for the tips @troutfisher on the custom settings. I've never really used them before, as I wasnt sure how much info it saved. Anyway I've just set up as following

C1 (Sports) Tv, AI Servo, Expanded (9points), +2/3 EC
C2 (People) Av, Single Shot, Single Point, +2/3 EC
C3 (Flash) Tv, Single Shot, Single Point , -1 2/3 EC

Common across all settings are:
Back Buton Focus
DOF Toggles between Single & AiServo in case of emergency.

1 question though, you mentioned about exposure being measured at release (not half press), where is the option for this. From what I can see on the 5D3, the shutter release can be either, AF & Metering Start / Metering start or AE Lock. Currently it is set to Metering Start is this what you mean?
Click to expand...

I think its AF+metering start but don't take my word for it , but please check in the manual or give Canon a call
 
I adopted the following method and i just found it easier to get on with.

Shutter button = AI servo
AF-on button (usually BBF) = Stop focusing

This means focus is always hunting when the shutter is pressed but if i need to lock in a particular focus i keep my finger on AF-on button. Muscle memory meant i couldn't get used to using the BBF method despite repeated efforts and this i picked up instantly. No going back now!
 
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