just got 7d, I am really frustrated right now.

Started Aug 27, 2012 | Discussions thread
caspianm Senior Member • Posts: 2,408
Re: Not so...

Jerry-astro wrote:

caspianm wrote:

I am confused...
To test and MC a lens you would use LV.
Once it is done and/or LV shot is fine then it should do equally well in VF.

I just don't believe the lens is fine in LV but oof using VF unless the camera is defective not the lens.

In fact, the opposite is true. LV uses a completely different mechanism to focus, where it's iteratively done directly from the image sensor (contrast detect). Using conventional focus (phase detect), a completely separate subsystem and sensor is used. If there's any chance for a calibration issue, it would be differences between what the phase detect AF subsystem (not LV) thinks is the point of focus vs. where it actually is. MFA is used to close that gap via a compensation factor. A correctly calibrated lens should have exactly the same results regardless whether you're using LV or focusing via the VF.

BTW, where LV comes in handy is to provide a "gold standard" for focus. If you're consistently seeing different results between LV and VF focus, it might be an indication that MFA is required. At that point, attempting to calibrate the camera/lens combo and determine an appropriate MFA setting should fix the issue assuming the lens doesn't have other issues requiring it to be serviced.

You are repeating what I said and then claim the opposite is true!!?

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