My Tamron 17-50mm is front focusing with used with the 580EXII AF assist beam

If I turn on the AF assist beam it will cause my lens to front focus.

But if I turn off the AF assist beam when using the flash it focuses fine.

I don't think it's the body because 7D and XSi both do this. And if I use Canon lenses (70-200is and 18-55is) with the AF assist beam on, they will focus fine.

This leads me to believe that something is wrong with the Tamron 17-50 lens?

I'm having a similar issue, but I think the problem is the flash.
Here is my post: https://photography-on-the.net …/showthread.php​?t=1386734

Have you solved this problem?
Thank you.

I had the same issue with a Tamron 17-50 on my 60D. It worked fine outside in the sun. Indoors, not so much. I sold it.

garycoleman wrote in post #9128064
If I turn on the AF assist beam it will cause my lens to front focus.

But if I turn off the AF assist beam when using the flash it focuses fine.

I don't think it's the body because 7D and XSi both do this. And if I use Canon lenses (70-200is and 18-55is) with the AF assist beam on, they will focus fine.

This leads me to believe that something is wrong with the Tamron 17-50 lens?

I use my Tamron 17-50 2.8 non-vc with a Yongnuo ETTL flash indoors and low light with no problems (with a 60D and XSi)