80D AI Focus

Started 5 months ago | Discussions
Todd G. Contributing Member • Posts: 923
80D AI Focus

I took photos of a family and 3-4 were totally (nothing in focus) out of focus and then the rest of the set would be.

Could being in AI Focus versus one shot account for this issue?  The family was static or moving slowly.

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Todd
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Leica Eye
Leica Eye Senior Member • Posts: 2,955
Re: 80D AI Focus
2

Todd G. wrote:

I took photos of a family and 3-4 were totally (nothing in focus) out of focus and then the rest of the set would be.

Could being in AI Focus versus one shot account for this issue? The family was static or moving slowly.

Aloha, it would be good to see the image... maybe your focus point was in between heads!! What Aperture were you using?   I use AiFocus - Single Shot -  Center Point Focus - 99.9% of my images are in focus..  L

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OP Todd G. Contributing Member • Posts: 923
Re: 80D AI Focus

I will post it tonight.  Nothing was in focus!

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OP Todd G. Contributing Member • Posts: 923
Re: 80D AI Focus

Both images were shot at ISO 500, 1/200, f/2.8, 52mm for the blurry one and 55mm on the clear one.

Focus was set to single point on the left side of the baby's nose.

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Ray UK Contributing Member • Posts: 808
Re: 80D AI Focus
3

AI Servo tends to be more reliable than AI focus for moving subjects ( or a moving photographer) also check in your camera menu for focus priority, there is a place where you can setup which takes priority when you press the button either obtaining focus or releasing the shutter.

Enders Shadow
Enders Shadow Veteran Member • Posts: 3,371
Re: 80D AI Focus
2

Todd G. wrote:

Could being in AI Focus versus one shot account for this issue? The family was static or moving slowly.

AI Focus starts off the same as One-Shot AF and switches to AI Servo AF mode only if it detects changing subject distance. It is slow to react and generally won't switch to AI Servo AF if the subject framing changes after initial focus lock has been obtained.

With AI Focus, if you don't have the subject correctly framed when you half press the shutter, it's unlikely to correct focus. (It behaves just like One-Shot AF) If you correctly place the AF point or zone over the subject, half press the shutter release, then have the subject start changing distance, eventually it will switch to AI Servo AF and begin to correct focus.

The EXIF of your examples show the camera was in One-Shot mode (didn't switch to AI Servo AF) when the pictures were taken. This suggests you probably didn't have the AF point located on the subject when you half pressed the shutter. If you want continuous AF, you should be using AI Servo. I've tested AI Focus several times and found it to be inconsistent and unreliable. I stick to AF modes where I know what the camera is doing.

For a scene like yours, I'd probably use One-Shot AF with the 9 point zone or a single point. Focus on half press then reframe or shift the AF point(s). I like seeing the AF lock indication.

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Dave
Dave Veteran Member • Posts: 5,639
Re: 80D AI Focus
2

I've never used AI focus.  It's the "mode in the middle" that I just skip.  Have you tried a smaller aperture, say f/4 or f/5.6 to see if focusing improves?  I use my 17-55 for similar shots and generally get better results shooting touch shutter in live view to put the focus where I want it.

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RedFox88 Forum Pro • Posts: 30,268
Re: 80D AI Focus
1

Todd G. wrote:

Could being in AI Focus versus one shot account for this issue? The family was static or moving slowly.

Avoid ai-focus as it doesn’t know what you wasn’t in focus. 
Use one shot, choose your focus point and understand depth of field to get your subjects with acceptable focus. I assume these people weren’t actually walking or running

OP Todd G. Contributing Member • Posts: 923
Re: 80D AI Focus

RedFox88 wrote:

Todd G. wrote:

Could being in AI Focus versus one shot account for this issue? The family was static or moving slowly.

Avoid ai-focus as it doesn’t know what you wasn’t in focus.
Use one shot, choose your focus point and understand depth of field to get your subjects with acceptable focus. I assume these people weren’t actually walking or running

Im going back to one shot and choosing my focus point since it works for me.  I was experimenting with AI Focus since the family had a baby and thought it would be good if he was active.

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RedFox88 Forum Pro • Posts: 30,268
Re: 80D AI Focus

Todd G. wrote:

RedFox88 wrote:

Im going back to one shot and choosing my focus point since it works for me. I was experimenting with AI Focus since the family had a baby and thought it would be good if he was active.

If you try anything with continuous focus try ai-servo and choose the autofocus point to be used. Ai-focus chooses the focus point to use which is pretty much the closest object to the camera

Dave
Dave Veteran Member • Posts: 5,639
Re: 80D AI Focus

RedFox88 wrote:

Todd G. wrote:

Could being in AI Focus versus one shot account for this issue? The family was static or moving slowly.

Avoid ai-focus as it doesn’t know what you wasn’t in focus.
Use one shot, choose your focus point and understand depth of field to get your subjects with acceptable focus. I assume these people weren’t actually walking or running

Doesn’t know what you want in focus?

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CameraCarl Veteran Member • Posts: 7,551
Re: 80D AI Focus
2

Using a simple depth of field calculator, a 55mm lens on an APS-C camera at f2/8 will give a range of about 3 inches of sharp focus; roughly half in front of and half behind the focus point. Perhaps your issue is not so much the camera's autofocus as your choice of f/2.8 and expecting the whole image to be in focus. Your second shot seems to support this: the child's face is mostly in focus but the rest of the image is not. Try f/8 if you want more of the photo to be in focus. This way you will get about 5 inches in focus on both sides of the focus point.

Duckman21 Forum Member • Posts: 87
Re: 80D AI Focus

My issue with AI Focus is not that it doesn't focus properly but that it often fails to track moving subjects. That said, I almost never use One Shot, in case an object does move slightly. For manual override I use the AF button to turn off AF (the opposite of back-button focusing)

I do recall reading somewhere that Canon bases its shooting speed measurements and other specs on AI focus rather than AI Servo

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