The Magic Photo Trick - Making People Disappear With A Wave Of the Hand
Leaving aside this intriguing mental picture ( though I hope it will disturb you for days...) we come to the bit of photographic history that had extremely insensitive recording materials and extremely dim lenses. And big sturdy wooden tripods. Using a plate camera on one of these with the lens stopped right down and a silver or glass plate with an ISO of 0.3 meant that the correct exposure of a Parisian street might be as long as 45 minutes. Long enough for the crowds that swirled through the street to pass by and not record on the plate - while the stationary buildings and other features did. We've all seen the ghostly picture of the street with just one leg on a shoe-black's box. it was the only living thing that was in one place long enough to record.
My bugaboo is people at car shows in front of the vehicles. I find the view I want but it is frequently blocked by the gawkers. They work in tag teams - as one finishes another steps in. I'm sure it is all a function of fluid dynamics and personal living space and bloody mindedness...I am debarred by foolish local laws from carrying a .44 and clearing the way myself - I must wait until they tire of the game and move off. Sometimes it is ten minutes wait until you can get 1/125th of a second for a clear shot.
I think it is time to think outside the square. And to think inside the square - the square of a 10 to 15-stop neutral density filter. Lee make 'em and they have a couple of sizes that would be suitable for use on a DSLR or mirror-less system.
Not cheap - Lee are never cheap - but the facility to increase an exposure in daylight from 1/125 of a second to 40 seconds or longer means that as long as the camera is on a tripod and no-one bumps it, the car will be recorded and the crowds passing in front of it won't. It may sound a bit drastic but then so is the .44 or bursting into tears or yelling " Fire!" to clear away the obstructions.
Note: Camera Electronic sell Lee systems in the shop and on-line. The standard 100mm holders, adapter rings, and Big Stoppers are a very popular sales item - every time there is a landscape photographer running a course in town the stock sells out. The Seven5 size...that's 75mm when they are not being twee...is the one for the mirror-less systems. There is a reduced-size holder and suitable Big and Little Stoppers. Look them up through the on-line store and follow along with the experiment.
I won't have the system in place for the Hyde Park Vintage Car Show but I might make it for the WA Hot Rod Spectacular.