I found out that handholding the lens at a shutter speed at 1/250s or less produced very blurry images. I did not use image stabilization for this test. By changing the ISO I could change the shutter speed w/o changing the lens aperture(range: ISO320-100). The picture labeled "tripod" was taken at ISO800 with a shutter speed of 1/1500s and with a cable release. The picture taken at 1/250s was taken at ISO160 and the picture taken at 1/180s was taken at ISO100.