You need to use a tripod when shutter speeds are really slow, right? Wrong! The degree of ‘shake’ that is evident in a picture may not be visible on your LCD screen or even on your computer, unless enlarged to a certain level. In such case, the overall sharpness of the image would appear soft, even if the shake isnt too obvious.
As a rule of thumb, the generally accepted shutter speed at which you can still shoot hand held is the converse of the lens focal length. In other words, is shooting at 150mm focal length, you need to use a shutter speed of at least 1/150 sec, or faster. This is just a rough idea, it varies from person to person depending on the stability of the hands.
What we’d advise is, if you are in a position to use a tripod, use it, whatever the shutter speed. This is especially true when shooting from unusual angles where your grip might not be as comfortable as usual (say for example top angle). Moreover, if you compose your shot while your camera is mounted on a tripod, you are free to move around, adjust the lighting, take light meter readings yourself etc.