… or ‘which was the thing to be proved’. I’m a big fan of sparkles produced by long exposures and I used to be quite good at them. But over the past year, I’ve been getting some disappointing results. At first, I put it down to operator fault, then weather, wobbly tripod and all sorts of other things. I then began to find I could get sparkles and fuzzy blurs in the same pic, which was curious. I wondered, therefore, whether it had something to do with the type of bulb used in the lights. And indeed, I think that is the case. I spent an hour doing some long exposures in Sloane Square this evening and all the short lanterns came out as fuzzy blurs (not shown) whereas the tall street lights definitely sparkled. So, the next stage is to establish the nature of the difference between the light sources. Answers on a postcard please!