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Occasional Contributor
Posts: 15
Registered: ‎04-13-2016

Autofocus woes

Canon D70, 85mm lens, 1/200 at f2.8

It's not sharp, even though the autofocus claims to have a good lock on. 

Judging by the tiles on the floor it's focused a good 1m too short.

Does the camera need servicing?

 

Also, what's with "the camera reports the distance as being between 2.88m and 11.9m" - that's a massive range given the 0.78m depth of field

 

Screen Shot 2019-02-27 at 5.41.43 PM.png


Original image at https://www.dropbox.com/s/agk1qtakqh9j4iz/_MG_6750.DNG?dl=0

Honored Contributor
Posts: 7,872
Registered: ‎08-13-2015

Re: Autofocus woes

[ Edited ]

@davetong wrote:

Canon D70, 85mm lens, 1/200 at f2.8

It's not sharp, even though the autofocus claims to have a good lock on. 

Judging by the tiles on the floor it's focused a good 1m too short.

Does the camera need servicing?

 

Also, what's with "the camera reports the distance as being between 2.88m and 11.9m" - that's a massive range given the 0.78m depth of field

 


As far as the camera reporting a distance between 2.88mm and 11.9m, that is called DOF, or Depth of Field.  One explanation for the wide range of distance is that it is reporting the focusing range of all of the active AF points.  That is a fairly old LR add-in, so it could be reporting incorrectly with more recent releases of LR.  

 

[The report shows 31 AF points on a camera that only has 19 AF points.]

 

Judging from the number of active AF points, combined with the fact that you are in focusing/ in AI Focus mode, it seems likely that the camera dial was set to Green [A], Automatic, to take the photo.  Or, maybe not.  In either case, experienced users avoid AI Focus like the plague, because it does not always lock focus before firing the shutter.  Stick to P mode, and One Shot focusing mode.

BTW, when an entire photo is evenly OOF throughout the entire frame, that points to one of two causes.  One, the cause is camera motion blur, or even blur from a moving subject.  Two, the camera/lens combo might need a focus calibration.

However, there is also a third more probable cause, IMHO.  It is the lens.  The EF 85mm f/1.8 USM does not focus very consistently.  It does not focus consistently enough to make bothering with an AFMA adjustment worth the time.  

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
Occasional Contributor
Posts: 15
Registered: ‎04-13-2016

Re: Autofocus woes

Thanks for the response.

The shot isn't OOF throughout the frame; as I noted, some of the tiles in front of the subject are in focus, which would

appear to rule out camera shake, rather it indicates to me that the camera had misjudged the distance by approx 1m. 


I'm not convinced that it's the lens; I've experienced similar problems when shooting with the 50mm 1.8 at low stops
I haven't had problems with the kit zoom lenses, but that's not surprising since they don't go wide enough
to create a shallow enough depth of field. Some other shots were pin sharp, which tends to rule out focus calibration.
If there is a problem it's either with the camera or the operator.


The shot was taken in manual mode, not automatic. I used to use AI Servo mode; I switched to AI Focus

because of the visual indication of focus lock (hollow laugh) - I'll try switching to One Shot and see if that helps.

I've never fully understood why, but Canon claims that the D70 has "up to 31 AF points" in Live View.
https://support.usa.canon.com/kb/index?page=content&id=ART142752
I wasn't shooting in Live mode so it's irrelevent, but I expect that's why the plugin reports the number.

Regarding depth of field, the plugin explicitly reports that as 7.02-7.80m, which is what I'd expect when shooting at f2.8

so that doesn't explain why the EXIF data reports the distance to the subject as being between 2.88m and 11.9m

VIP
Posts: 10,922
Registered: ‎12-07-2012

Re: Autofocus woes

Stop using AI-focus mode and you will be fine.

EOS 1DX and 1D Mk IV, even less and less other stuff.
VIP
Posts: 10,922
Registered: ‎12-07-2012

Re: Autofocus woes

"...some of the tiles in front of the subject are in focus..."

 

I don't think so. They have more contrast but still look OOF to me.

EOS 1DX and 1D Mk IV, even less and less other stuff.
Occasional Contributor
Posts: 15
Registered: ‎04-13-2016

Re: Autofocus woes

[ Edited ]

Here's a better example:

https://www.dropbox.com/s/ius8xoh48ntrzv0/_MG_7079.DNG?dl=0

 

This was taken in Manual mode, using One-Shot focus. Same body and lens.

The leaves and the tree in the upper left and the gravestones on the right are sharp,

but the focus locks are supposed to be on the crypt in the distance.

 

I'm going to try cleaning the AF sensors

 

Screen Shot 2019-03-01 at 10.21.00 AM.png

Highlighted
Honored Contributor
Posts: 7,872
Registered: ‎08-13-2015

Re: Autofocus woes

Do not clean it. Your photo is in focus. But, there multiple AF points indicating a potential to lock.

You cannot accurately determine which AF point was used to focus the lens. My guess says the AF point over the nearest object to the camera, which would be the tree on the left.
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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
Occasional Contributor
Posts: 15
Registered: ‎04-13-2016

Re: Autofocus woes

[ Edited ]

It really is not in focus. Here's a closer look. The tree with the focus point is out of focus.
None of the supposed focus points are actually in focus.

The tree to the left of it, which is a good few meters closer to the camera, and the gravestone beside it are sharp.

You can download the full DNG file from the Dropbox link

https://www.dropbox.com/s/ius8xoh48ntrzv0/_MG_7079.DNG?dl=0



Screen Shot 2019-03-01 at 12.27.49 PM.png

Occasional Contributor
Posts: 15
Registered: ‎04-13-2016

Re: Autofocus woes

Screen Shot 2019-03-01 at 12.26.10 PM.pngScreen Shot 2019-03-01 at 12.26.45 PM.png

Frequent Contributor
Posts: 63
Registered: ‎11-14-2018

Re: Autofocus woes

The first pic you showed us did not have the tree on the left, did you crop it out?  Did it have a focus point also.  It appears to be the closest item in the pic, which the camera may have "correctly" focused on.

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