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1 pt autofocus is inaccurate

Andysdn
Apprentice
I have an EOS 70D with an EF-S 18-135 1:3.5–5.6 IS STM and EF lens 50mm 1:1.8 lens.

I typically shoot in 1pt autofocus and have realized that various points are inconsistent. For instance, when I place the camera on a tripod with the 18-135 and shoot using the center point my shot is sharp. However when I focus using an outside point the subject is completely out of focus.

I tried this same test with the 50mm and it’s better but but it still seems to be less sharp on the outside, just not nearly as bad as the 18-135.

Is the 18-135 lens faulty or is there a camera setting that will fix this? At this point I’m ruling out technique as a the culperate.

5 REPLIES 5

Andysdn
Apprentice
I should also note that I’ve always had focus issues with this lens. I only recently tested each point for accuracy

When you are not using center point "only" which is what I use 90% of the time, the cameras focuses on the closest thing.  Whether it is your intended subject or not.  I suspect that is what you are noticing. In other words what you think is in focus is different than what the camera thinks.

 

If you want precise focus on something turn off all the other focus points and use just the center.

EB
EOS 1DX and 1D Mk IV and less lenses then before!

Waddizzle
Legend
Legend

@Andysdn wrote:
I have an EOS 70D with an EF-S 18-135 1:3.5–5.6 IS STM and EF lens 50mm 1:1.8 lens.

I typically shoot in 1pt autofocus and have realized that various points are inconsistent. For instance, when I place the camera on a tripod with the 18-135 and shoot using the center point my shot is sharp. However when I focus using an outside point the subject is completely out of focus.

I tried this same test with the 50mm and it’s better but but it still seems to be less sharp on the outside, just not nearly as bad as the 18-135.

Is the 18-135 lens faulty or is there a camera setting that will fix this? At this point I’m ruling out technique as a the culperate.


Are your subjects moving or stationary?

 

I suggest that you use One Shot mode, not AI Servo mode to take test shots.  Then, use DPP to see where the active AF point was located in the frame.  The center AF point is also the most sensitive and most accurate.  I would rather lock focus, and recompose the shot than use the center in One Shot mode.

--------------------------------------------------------
"The right mouse button is your friend."


@Waddizzle wrote:

@Andysdn wrote:
I have an EOS 70D with an EF-S 18-135 1:3.5–5.6 IS STM and EF lens 50mm 1:1.8 lens.

I typically shoot in 1pt autofocus and have realized that various points are inconsistent. For instance, when I place the camera on a tripod with the 18-135 and shoot using the center point my shot is sharp. However when I focus using an outside point the subject is completely out of focus.

I tried this same test with the 50mm and it’s better but but it still seems to be less sharp on the outside, just not nearly as bad as the 18-135.

Is the 18-135 lens faulty or is there a camera setting that will fix this? At this point I’m ruling out technique as a the culperate.


Are your subjects moving or stationary?

 

I suggest that you use One Shot mode, not AI Servo mode to take test shots.  Then, use DPP to see where the active AF point was located in the frame.  The center AF point is also the most sensitive and most accurate.  I would rather lock focus, and recompose the shot than use the center in One Shot mode.



@Waddizzle wrote:

@Andysdn wrote:
I have an EOS 70D with an EF-S 18-135 1:3.5–5.6 IS STM and EF lens 50mm 1:1.8 lens.

I typically shoot in 1pt autofocus and have realized that various points are inconsistent. For instance, when I place the camera on a tripod with the 18-135 and shoot using the center point my shot is sharp. However when I focus using an outside point the subject is completely out of focus.

I tried this same test with the 50mm and it’s better but but it still seems to be less sharp on the outside, just not nearly as bad as the 18-135.

Is the 18-135 lens faulty or is there a camera setting that will fix this? At this point I’m ruling out technique as a the culperate.


Are your subjects moving or stationary?

 

I suggest that you use One Shot mode, not AI Servo mode to take test shots.  Then, use DPP to see where the active AF point was located in the frame.  The center AF point is also the most sensitive and most accurate.  I would rather lock focus, and recompose the shot than use the center in One Shot mode.


That doesn't make sense to me. Did you mean to say "I would rather lock focus and recompose the shot than use anything but the center in One Shot mode"?

Bob
Philadelphia, Pennsylvania USA

“That doesn't make sense to me. Did you mean to say "I would rather lock focus and recompose the shot than use anything but the center in One Shot mode“

 

You are correct.   It did come out backwards,  I meant exactly what you wrote.  Bad eyes failed me again.

--------------------------------------------------------
"The right mouse button is your friend."
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