Take the test

To find out how slow a shutter speed you can use with your camera and lens, shoot a subject with lots of fine detail and check the images on a computer at 100% on screen. Ideally, shoot 10 or so images at each focal length and shutter speed as this enables you to calculate your hit rate. If, for example, you find that 5/10 of your images are sharp at one particular setting, you’ll know that you need to shoot at least two images to be reasonably confident of getting a sharp result.