Rebel T6S and EF 85mm 1.8 soft images using optical viewfinder autofocus

[Eric635]

Hi all -

I recently got the Rebel T6s.  I've been noticing bad autofocus with the ef 85mm f1.8 lens.  Most images are soft and more so as the distance to the subject increases (im guessing front focused?).  Whether using single point AF, zone AF or full autofocus, the same results keep happening.  Switching to manual focus and single point AF seems to help somewhat.  Also, I had set up on a tripod, shot an image using Live View AF and compared the same shot to the optical viewfinder single point AF.  Live view is sharp, whereas the viewfinder image is soft.... I know the phase detect AF and contrast detect AF differ, so I wonder if this points to the lens / camera body combination being an issue.  

This same lens produces quite sharp images on my rebel t3i with no AF issues that i can notice

Also, on my new Rebel T6s i have used the ef-s 24mm stm lens and do Not notice softness using the optical viewfinder AF other than your normal hit/miss rate while handheld shooting.  

So, my question I guess is does this point to the lens or would it be an AF issue with the body?  I know the rebels don't have micro AF abilities, so im not sure what to do.

thanks!  

[ebiggs1]

Check to see if the dioptor is off in the viewfinder.

[jrhoffman75]

Certainly check diopter first, but since you state - "Switching to manual focus and single point AF seems to help somewhat" it sounds to me that it is a potential AF mismatch between lens and camera.

1. I've been noticing bad autofocus with the ef 85mm f1.8 lens.  Most images are soft and more so as the distance to the subject increases (im guessing front focused?).  Whether using single point AF, zone AF or full autofocus, the same results keep happening. (I am assuming you verified this in actual image on computer or camera LCD.  Are images soft in viewfinder and on computer?)  

2. Switching to manual focus and single point AF seems to help somewhat.  (Diopter adjustment affects clarity of image viewed on groundglass screen. It would not affect focus of lens; sounds like you are saying you can get sharp viewfinder image if you manually focus.)

3. I had set up on a tripod, shot an image using Live View AF and compared the same shot to the optical viewfinder single point AF.  Live view is sharp, whereas the viewfinder image is soft (Can you get a sharp viewfinder image by manually foucing?).... I know the phase detect AF and contrast detect AF differ, so I wonder if this points to the lens / camera body combination being an issue.  (This is one way some folks use to micro-focus-adjust. Focus using LiveView and then dial in MFA until the lens doesn't refocus when using autofocus.)

4. This same lens produces quite sharp images on my rebel t3i with no AF issues that i can notice

5. Also, on my new Rebel T6s i have used the ef-s 24mm stm lens and do Not notice softness using the optical viewfinder AF other than your normal hit/miss rate while handheld shooting.  (Greater DOF of 24mm lens would mask MFA error.)

[ScottyP]

Agree. Your DOF on a 24mm lens is huge compared to that of the 85mm so you might not notice slightly OOF shots.

Since there is no AFMA on the T6s I would return the camera and try another copy, now, before it is too late to return, rather than getting into the hassle of sending body and lenses to Canon for adjustments.

[amfoto1]

Some T6i/T6s got sent out with lots of spots on the sensor and Canon moved quickly to correct the problem, but it's possible you got one of those. This would probably make for softer images, depending upon what lens aperture is being used and it  might be more apparent with one lens than another.

If your camera has serial number 01xxxxxxxx or 02xxxxxxx you should inspect it to see if this problem is occuring. If it's been corrected, there will be a black dot inside the battery cover door. You can find illustrations and more info about this here: http://www.canonrumors.com/2015/05/canon-responds-to-rebel-t6it6s-sensor-issue-with-service-advisory/

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
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