canon t3i focusing issue

[montano_751]

my t3i isn't focusing sharply at all regardless of the settings.. i'm not beginner so i know its not my settings or me.. what else can it be??

[RobertTheFat]

On all lenses or on just one lens? Was it working all right and then went bad, or was it always bad? If you're not a beginner, you know you haven't given us enough information to go on.

[montano_751]

I use a 50 1.8 and 50 1.4 and its worse on my 1.4

[RobertTheFat]

---

@montano_751 wrote:
I use a 50 1.8 and 50 1.4 and its worse on my 1.4

---

It's not surprising that it's worse on the 1.4 than on the 1.8, but the fact that it happens at all is obviously a cause for concern. Does it consistently front-focus or consistently back-focus? If so, the camera's AF mechanism may be out of adjustment. Unfortunately, the T3i doesn't have AF microadjustment, so trying that isn't an option. Before you send it in, though, it might be helpful to see how those lenses behave on a different body.

[montano_751]

Yes it does front and back focus often can't tell which one it does more but I noticed on my last shoot I was focusing on my backdrop instead of the subject. Ugh!!! I'm meeting a photog friend and will use the lens on hers to see.. So if the lens perform fine on hers. What should I do next with mine? Is it worth fixing ??

[ebiggs1]

"Yes it does front and back focus often can't tell ..."

The lens can't do both.  If it is truly missing both front and back, it isn't fornt or back focusing.  It is simply OOF.

The easiest thing to do is, like Bob from Boston says, try it on a different camera.  Also try another, her lens, on your camera.

At this point, you must find out which is at fault.  Then decide your course of action.

 If it is the 50mm f1.8, it is a throw away.  If it is the 50mm f1.4 you can check on service cost as it may be a toss up.  If it is the T3i you will need to get an estimate, as it too may be time to upgrade.

 If it is "you", you need to change your shooting habits!  

[TCampbell]

You're going to need to do some testing to find out what the lens and camera is doing.

I have a Spyder "LensCal" focus test chart, but you can download and make your own test chart. Here's a link to a pretty good chart: http://regex.info/blog/photo-tech/focus-chart

Download and print the chart. Read all of the instructions. The camera needs to be on a triopd. You have to remove any possibility that the camera moved after it locked focus.

I run focus all the way in (closest focus distance) then make the camera auto-focus and take the shot... repeat this about a half-dozen times. THEN... run the focus all the way out (focus to infinity) and take another half-dozen shots.

What you want to know is if the camera & lens combination is front focusing vs. back-focusing. Also... does it make a difference if the motors had to run the focus out (from minimum focus) vs. run the focus in (from max focus distance.)

If the camera consistently misses focus and always in the same direction (missing focus just once or twice is an outlier... you want to see if it's consistent) then it means the camera has to be sent to Canon for service (they can re-shim the sensor). On higher end camera models, Canon allows for micro-adjustment of the auto-focus system that can be performed by the end user (and it can even be set to a different adjustment for each lens.) But the T3i doesn't support auto-focus micro-adjustment (typically the mid-range and high-end cameras support it.)