T3i Focus Issue?

[mblair623]

Is there a way to check the focus on a T3i?  I intermittently have photos that even though I focus on the center of the subject, it focuses on the nearest object which is usually off-center?  I have checked the lens and it is on AF.  

[shadowsports]

Greetings,

What lens are you shooting with?  I take it you feel that the gentleman in the center of the group is slightly out of focus?  He was the intended focus point?

What aperature is the lens using?   Sometimes the AF will grab onto the closet subject.  This can happen with off axis subjects, in low light or if you have a semi transparent object in the foreground.  (Just an example, I realize not in this case).

If you are using  a low aperture and the AF grabs onto a closer subject, another subject as little as 3ft away might not be as sharp as you would expect.  If you have made changes to your cameras settings recently or are using a "new" to you lens, you can try resetting the camera to defaults and perform a few test shots again to establish a baseline.

May also be worth while to look at this thread as well;

http://community.usa.canon.com/t5/Lenses/Autofocus-not-working-18-55mm-lens/m-p/138114#M5459 

[BurnUnit]

Here's the EXIF data if it helps.

• Exposure Time (1 / Shutter Speed) {0x829A} = 1/60 second ===> 0.01667 second
• Lens F-Number / F-Stop {0x829D} = 9/2 ===> ƒ/4.5
• Exposure Program {0x8822} = normal program (2)
• ISO Speed Ratings {0x8827} = 400
• Sensitivity Type {0x8830} = recommended exposure index (REI) (2)
• Recommended Exposure Index {0x8832} = 400
• EXIF Version {0x9000} = 0230
• Original Date/Time {0x9003} = 2017:11:23 13:12:06
• Digitization Date/Time {0x9004} = 2017:11:23 13:12:06
• Components Configuration {0x9101} = 0x01,0x02,0x03,0x00 / YCbCr
• Shutter Speed Value (APEX) {0x9201} = 6/1
  Shutter Speed (Exposure Time) = 1/64 second
• Aperture Value (APEX) {0x9202} = 35/8
  Aperture = ƒ/4.56
• Exposure Bias (EV) {0x9204} = 0/1 ===> 0
• Max Aperture Value (APEX) {0x9205} = 1976/453 ===> 4.36
  Max Aperture = ƒ/4.53
• Metering Mode {0x9207} = pattern / multi-segment (5)
• Flash {0x9209} = n/a (9)
• Focal Length {0x920A} = 32/1 mm ===> 32 mm
• Last Modified Subsecond Time {0x9290} = 90
• Original Subsecond Time {0x9291} = 90
• Digitized Subsecond Time {0x9292} = 90
• FlashPix Version {0xA000} = 0100
• Colour Space {0xA001} = sRGB (1)
• Image Width {0xA002} = 5184 pixels
• Image Height {0xA003} = 3456 pixels
• Focal Plane X-Resolution {0xA20E} = 97379/17 ===> 5728.18
• Focal Plane Y-Resolution {0xA20F} = 331079/57 ===> 5808.4
• Focal Plane X/Y-Resolution Unit {0xA210} = inch (2)
• Custom Rendered {0xA401} = normal process (0)
• Exposure Mode {0xA402} = auto exposure (0)
• White Balance {0xA403} = auto (0)
• Scene Capture Type {0xA406} = standard (0)
• Body Serial Number {0xA431} = 1520xxxxxxxxx
• Lens Specification {0xA432} = 18-135mm F0-0
• Lens Model {0xA434} = EF-S18-135mm f/3.5-5.6 IS
• Lens Serial Number {0xA435} = 0000xxxxxx

[Waddizzle]

A shutter speed of 1/60 second is not very fast,  In fact, is very slow to use with moving subjects.  What was the focal length setting of the lens?

As a general rule, when you are using a full frame sensor camera, you want a minimum shutter speed of 1/FL, where FL equals your focal length.  With an ASP-C camera, which crops the image, you need to go even faster.  I recommend going twice as fast as you would with a full frame, 1/(2*FL).  Note these are recommended minimum settings.

The onboard flash will typically give a shutter speed of 1/200 second.  This is a good speed to use when photographing people who are generally standing still.  Of course, the faster the shutter speed, all the better.  Fast shutter speeds will freeze any motion by the subjects in the frame.  When I shoot sports like football, use 1/1600.

You have a two fold problem.  Manually select the center AF point.  Use a faster shutter speed, like 1/200.  

BTW, if you did not use a flash, then what is the light source in your posted image?  It almost looks like a flash was used.

[BurnUnit]

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@Waddizzle wrote:

 BTW, if you did not use a flash, then what is the light source in your posted image?  It almost looks like a flash was used.

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Well now you've got me curious too. I also assumed a flash was used but the EXIF data doesn't clearly state one way or the other. Maybe a third party flash...?

[mblair623]

I don't know if the built-in flash came on or not.  If it didn't the only thing behind me is the door leading to outside porch (it was a sunny day).

[Waddizzle]

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@mblair623 wrote:

I don't know if the built-in flash came on or not.  If it didn't the only thing behind me is the door leading to outside porch (it was a sunny day).

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If the door was open to a sunny day, then where is your shadow.  You should be standing between the light source and the subjects.

[ebiggs1]

"... it focuses on the nearest object which is usually off-center?"

That is the normal way it's done.  Turn off all the focus points except the center one.

You can shoot in Sports mode with a T3i, the camera bases focus on the center focus point. In the other fully automatic exposure modes (Scene Intelligent Auto, Portrait, Landscape, and so on) as well as in Creative Auto and A-DEP mode, the camera’s autofocusing system looks at all nine autofocus points when trying to establish focus. Typically, the camera sets focus on the point that falls over the object closest to the lens. 

To choose a single autofocus point, set the camera to Manual AF Point Selection mode.

1. You can shift from Automatic AF Point Selection mode to Manual mode in two ways:

   • Rotate the Main dial. This option is easiest when you’re looking through the viewfinder.

   • Press the Set button. Pressing the button toggles the camera between Automatic AF Point Selection and Manual AF Point Selection with the center point activated.

2. Specify which AF Point you want to use.

   You can either rotate the Main dial or press the cross keys to select a point. When all autofocus points again turn red, you’ve cycled back to automatic AF Point Selection mode. Rotate the dial or press a cross key to switch back to single-point selection.

[Waddizzle]

Always use OneShot focus mode, unless you are tracking a subject whose distance to the camera is constantly changing, which is when you could use AI Servo. 

Always manually select the center AF point, because it is the most accurate one in your camera.  Do not let the camera choose an AF point for you.  Take control.

I suggest always using P mode to take photos.  This is the best mode to use learn about both camera settings and exposures.

[Tim]

Hello mblair623, 

You can check the which focus points are being used by opening the image within the Digital Photo Professional software.  From the main screen, double click an image to bring it into a new window.  Then, right click and choose the option to display AF points. This will allow you to verify the points which were active at the time of exposure.