You're Correct!
Just like any of the other 13 clubs in your golf bag, your putter has a sweet spot. Now you may think that this would be right under the alignment line that the manufacturers put on the top of the head, but this is not always the case, especially if you use an older putter or a heel shafted putter (where the shaft is set into the heel end of the head).
If you want to find the true sweet spot of your putter then youre going to need to get a pencil with an eraser on the end, a marker pen and your putter.
Hold your putter at the very top of the handle with your thumb and forefinger, and make sure that the putter face is looking at you, almost as if you were the ball. Take your pencil and with the eraser end tap the face of your putter. Start at the toe end and work your way across to the heel. You will notice that when youre tapping around the toe and heel ends that the face just twists, but when you tap towards the middle of the face the putter starts to move away from you, the face remains looking at you. This is were the sweet spot is located so you now need to tap in and around this area and see where your face is at its most stable. This will be the true sweet spot.
Now you would assume that most of the manufacturers who put a mark or marks on the top of the putter to help you align have placed these right over the sweet spot, but this is not always the case. Take your marker pen and make a small mark above the area you tapped when the face stayed at its most stable. If it is where the manufacturer has also marked then that is fantastic, but if not, make your mark big enough so you can use it when you set up. From here, you know that the sweet spot of your putter is set up to your ball. This will give you the opportunity to roll your putts true.
Sorry Try Again! - See Explanation Below
Whether or not you have to hit the ball hard with your putter, you still need to find the measured centre (sweet spot). Most of the putts you will hit with control unless you have an exceptionally long putt, and even then it is vital that you hit the sweet spot to give you the best chance of hitting your putt the desired distance.
Sorry Try Again! - See Explanation Below
Whether you use a wood, an iron or your putter, the size and positioning of the sweet spot is exactly the same, in the measured centre. The actual size of the sweet spot is the size of a pin head, and its how the head weight is distributed around the perimeter that creates the amount of forgiveness.
Sorry Try Again! - See Explanation Below
You will always find the sweet spot of a putter in the measured centre, no matter how big or small the face is. How much forgiveness for off centred hits will depend on how much weight is placed around the heel and toe areas of the head, and also how far back from the face the weight is placed.
The more weight further back and at either end of the head, the greater resistance to twisting the putter head will have when hitting the ball off centre.