1st Gen 70-200 2.8 IS focus issues

[dcsimages]

I'm having an issue with inconsistant focusing at 2.8 to 4.5. 

I'm doing tight portrait at 200mm, not at the closest focusing distance though and focus point from shot to shot is shifting from dead on to half an inch back or front focused at random. When I look at the focus points in DPP they're just where they should be, but around 30% of the time the focus is just slightly off.

I've just started try to shoot with this shallow a depth of field. I always tried to shoot with this lens in the past around ƒ8 - ƒ11 as that's where it's sharpest, but I'm working on a new shallow depth porfolio.

I'm shooting in single shot, half press shutter button, and picking the closest focus point and setting it on the inner corner of the closer eye.

Would either of the AI modes help? Does tracking help if the subject is moving very slightly back and forth and than across the frame?

Would shooting bursts help?

I've tried back button AF, but all the buttons I could use to start and stop it are awkwarding placed on the camera for my hands.

[wq9nsc]

When you are shooting at very shallow depth of field, the AF calibration has to be spot on for the lens and most newer/better  Canon cameras make it easy to do that calibration.  Here is a link to the Canon microfocus adjustment guide:  https://cdn.static-bl.com/images/manual/Canon-AF-Micro-Adjust-Guide.pdf

The forum strips some links and Canon's USA website probably has their guide on it but searching that site is an exercise in frustration so if the link gets stripped just google Canon micro focus PDF and several links to their guide will show up.

Rodger

[dcsimages]

The shots are not off consistently in the same direction, but a focus micro adjustment is the first thing I checked.

[Waddizzle]

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@dcsimages wrote:
The shots are not off consistently in the same direction, but a focus micro adjustment is the first thing I checked.

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If this means the lens is not the problem, what other source of [error] is there?  

Like I said, contact Canon Support.  Let them help you firgure out the issue. 

FREE TIP:  I never use Spot Focus handheld, only on a tripod.

[dcsimages]

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@Waddizzle wrote:

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@dcsimages wrote:
The shots are not off consistently in the same direction, but a focus micro adjustment is the first thing I checked.

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FREE TIP:  I never use Spot Focus handheld, only on a tripod.

I wrote several times that I'm shooting on a tripod, but apparently reading comprehension is not your strong suit.

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[Porcha]

Be nice everyone! 

[ebiggs1]

Porcha may I ask what was not "nice"?  Perhaps some clarification would help us as I saw nothing not nice or offending.  If a person decides to reject our advice it isn't because we are not being nice.  It is what we believe will help.

[Porcha]

Please be respectful of everyone's opinions, belittling someone's opinion can be offensive. We can all agree to not agree on things. 

[ebiggs1]

Sorry I still do not know what I said to offend the OP.

[Waddizzle]

"When I look at the focus points in DPP they're just where they should be, but around 30% of the time the focus is just slightly off."

You might need a focus adjustment.  I'm curious as to what camera body are you using, though.  Not every camera offers AFMA.  An old and weak battery can cause focus to be inconsistent, too.  I just had to order a pair for my 7D2.

Using back button focus does not improve focusing.  It can only improve your, meaning you not the camera, ability to acquire a subject for focuing under certain shooting conditions.

[EDIT] How many focus points do you have active?  Try using just the center AF as the only active AF point.