I purchased the Tamron SP 15-30mm f/2.8 Di VC USD G2 lens with the intent of doing time lapse photos at 4 second intervals. The pictures had exposure variations like in the old audio days we would call wow and flutter. There would be a properly exposed sequence then a series of over or underexposed pictures then another series of properly exposed pictures. This happens throughout the sequence whether it is 500 images or 2000+ images. Because of the variance in the exposure, I can’t create a time lapse video. I just received an new lens on exchange with a higher serial number but it does the same thing. Is this a design problem or am I pushing the lens to hard? I don’t have any problems with my 28-300 Nikon zoom. Thanks for your feedback, Richard.