# I'm having some trouble with focus



## sleining (Jan 26, 2013)

If you notice,the left side of the photo of out-of-focus. Occassionally, I have this problem and don't know what causes it   I have a Canon 7D and the lens I was using is a 28-135.  I was using flash. Any suggestions are appreciated.  The photo has to be viewed larger in order to see the lady in black out of focus.


----------



## o hey tyler (Jan 27, 2013)

Assuming the frame in the middle is fairly parallel to the sensor plane, your lens could be defective or have an element out of whack. When was the last time you removed the lens from your body? Also, if the person on the left side was standing farther back than the other two, she could just be outside of the DoF.


----------



## subscuck (Jan 27, 2013)

Looking at it full size, I see the following:

The only subject fully in focus is the lady on the right.
The frame is not parallel to the sensor plane as it is also oof on the left side
The background also goes from in focus to oof as you move right to left
The lady in the middle is slightly oof, tho not as bad as the lady far left
I realize you already know all of this, but it leads to the following:

You weren't parallel to the subjects, and at f4, with a 30mm fl, this close to your subjects (unless this has been cropped), you're a victim of dof being too shallow. If you're using flash, you can stop down and eliminate the problem.


----------



## cgipson1 (Jan 27, 2013)

+1  ^^ I think Subscuck has it... that was my first thought!


----------



## TCampbell (Jan 27, 2013)

I'm suspecting the lens BECAUSE not only is the lady on the right focused... but look at the fabric BEHIND her.  It's relatively in focus.  Meanwhile... on the left side, nothing is in focus at any distance.

If you were to use a "tilt" shift lens, you'd "tilt" the lens to angle the depth of field.  I could reproduce this effect with my tilt-shift just but tweaking over the tilt angle slightly.  If the lens elements were all parallel to the sensor plane then I'd expect to see something in focus at some distance on the left side... but from her fingers in the foreground to the fabric in the background it's all soft.

If you suspect an issue with the lens, test it.

Grab a sheet of newspaper (news print), and tape it flat on a wall.  Put the camera on a tripod so that the sensor plane is also flat to the wall (so that when one part of the newspaper is in focus, the whole thing should be in focus.)  Take test shots at different f-stops.  

Use newsprint because you can use the fine printing to tell if the image really was in focus or not as it's a high contrast pattern.

Does it ONLY happen with this lens?

The sensor is suspended by three "shim" screws which can be adjusted.  If it happens with EVERY lens then it could mean the sensor inside the camera isn't level and needs to have it's shim screws adjusted (you'd have to send it in for this... it's not a user-serviceable adjustment.)


----------



## sleining (Jan 31, 2013)

Thank you! I will try everything before taking it in. It's not that old, so thinking I shouldn't be having issues like this because of camera malfunctions.


----------



## michaelanthony (Feb 1, 2013)

a few years ago, i went through 2 different Canon 28-135 lenses and they were junk... i later heard several stories from other shooters about focus issues with that lens... i have since switched out to the 24-105 4L and love that one...


----------

