My mum used to make this quince jelly every Autumn courtesy of our neighbour who had an enormous quince tree.
Quince jelly has a lovely amber colour and a delicious fragrant taste. Make sure you save the pulp to make quince paste (membrillo).
In this recipe the quantity of sugar does vary. The general rule of thumb is to measure how much juice you have and add the same volume of sugar.
Quince might be a little hard to come by. Look out for them at your local farmers market or ethnic shop (I bought mines from TFC). They are well worth the trouble!