Problem shooting at F2.8

[Melon2560]

I am experiencing a problem shooting at F2.8 with Tamron 25-78 2.8 di.

Everytimw i shoot something at f2.8 the edges of the subject develops a fuzzy area CA like problem (as seen in photo) but yet if i shoot at F5 it perfectly fine. 

What would cause this type of issue 

[Damien Symonds]

Hi, I've moved your post into @Brian's section, because he's the guru for camera-related stuff.  He'll be along shortly.

I imagine it will help him if you can tell him all the specs of this shot - ISO, shutter speed and so on.  In fact, it might be even better if you can show him a screenshot of those details from Lightroom.

[Brian]

On 12/1/2017 at 10:58 AM, Melon2560 said:

What would cause this type of issue 

A defective lens. It needs to be sent in for repair. That problem is not normal at all.

Now, there are Depth of Field challenges when shooting at f/2.8, but that isn't the case at all.