On 27/3/05, Don Sanderson, discombobulated, unleashed: >Cotty this is probably going to make me feel stupid (so what's new?), >but I have to ask.
Hey, I can bluff with the best of them :-) >In the first and fourth photos there is what appears to be a distinct >'shadow' behind the ball. It makes it look as though the sky was a >backdrop, or that the ball was pasted n later. Yes, it does - like a drop-shadow effect... >What causes this? Short answer - exposure. Long answer: I would guess that it's all to do with the duration of the exposure and the fact that the ball is moving through the air during. The exposure on pic number 4 is 1/15th second at f/8 (ISO 320) - so lets re-arrange things slightly, let's try this: Point the camera up at the sky, set to ISO 320, and shoot at 1/15th at f/ 8, with no flash. What do you get? An evenly exposed sky. Obviously, depending on how bright the sky is, it might look just like the majority of the sky visible in pic number 4. Let's assume it is. Now shoot the sky again, this time, throw a ball across the frame while the exposure is made. At 1/15th sec, the ball will obviously not be perfectly frozen in the air, it will be blurred and take on a different shape - more a like a comet - with a round front (in the direction of travel) and a blurry tail. However, at 1/15th sec, with the sky nicely exposed and no flash, the ball will be silhouetted against the sky, so the effect will be a comet-shaped dark area across the nice blue sky. Now, same again, this time add a flash, and the ball will be frozen at the point of the flash firing. If it is on a second-curtain sync setting, then the flash fires right at the *end* of the 1/15th sec exposure, and what is a typical flash duration? 1/20,000th sec? So - now we get the same comet shaped area (the ball) across the frame, but the leading edge of the shape - the actual ball - is now illuminated by the flash. The part of the ball not illuminated by the flash, which is also blurry, is the dark area 'behind' the ball. So - the shadow is actually the ball as it travelled through the frame and before it was lit by the flash. Sorry about the roundabout way I reached this conclusion, but basically thought about it as i typed ;-) Now off to make pizzas as the Mrs has offered to physically remove my typing digits unless I do so immediately.... HTH Cheers, Cotty ___/\__ || (O) | People, Places, Pastiche ||=====| http://www.cottysnaps.com _____________________________
