Curtain shutters and egg shaped wheels

**Jim Galli** · 23-Jan-2010, 23:24

In Jacques Lartigue's famous early racing car pictures, I understand the people leaning because I think that J. H. L. was panning the camera hand held, so anything stationary would be at a different place as the shutter moves down, and if he is in fact 'panning' I can see that the car would be reasonably sharp at an effective 1/1000th second, but why are the wheels egg shaped? Why does the camera see them any differently than the car body?

I want to re-create this effect with a Model T speedster at speed using my 5X7 Speed Graphic. I know Lartigue likely used a chimney graflex type, but if I prefocus for a known distance that the car will be at speed, that shouldn't make any difference. I'll hand hold and 'pan'. Could even build a wire 'sports frame' like the later press 4X5's had.

**Paul Ewins** · 24-Jan-2010, 00:05

From what I understand of it (and it made sense *at the time that I read it*) the effect happens not because you are panning but because the actual speed that the shutter runs at is quite slow, even although a narrow slit will give an effective 1/1000 speed.

So, with the camera held stationary and an object moving past quickly, when the shutter slit starts moving the object is in position X, by the time it has moved down 4" the object is in position x+1 so the top and bottom don't align. Because the curtain moves from top to bottom and the image is upside down the bottom of the image, i.e the wheels, is recorded first and as the car move across more of it is recorded untl it finishes with the top of the image. This is why the car always leans in the direction it is travelling.

Most older 35mm SLRs had shutters that moved horizontally so this wasn't an issue. The newer ones with vertical shutters should display the same effect, but with a travel time of 1/150 - 1/250 sec compared to (I think) 1/5 sec for the Graflex it is going to be so slight that you won't pick it up.

**Jim Galli** · 24-Jan-2010, 00:29

The Graflex had an effective 1/1000th speed. It had 6 different possible speeds of travel, and 4 different widths of slit opening. 1 1/2", 3/4", 3/8" and 1/8" slits all gave different speeds. So 24 possible different speeds all the way from 1/30th to 1/1000th.

So perhaps to get the egg shape wheel, the camera should stay still, or pan slightly slower than the moving vehicle. If the camera were held static, the "people" wouldn't be angled in the photo I linked to.

**Stephane** · 24-Jan-2010, 00:50

This is as explained by Leslie's Stroebel "view camera techniques" on page 76: first he used a focal plane shutter, then he panned.
The car is not distorted because Lartigue panned and the wheel is elliptical because of its rotation. The panning caused tilted of the people and vertical poles in the opposite way of the elliptical wheel.

**Steven Barall** · 24-Jan-2010, 06:47

I think the car body is more distorted than you think it is. Also, because you can freeze the forward motion of the car doesn't mean that you can freeze the rotation of the wheels especially with a spoked wheel where the rotation is obvious. Good luck. I look forward to seeing the photos you make.

**Gordon Moat** · 24-Jan-2010, 12:25

First is focal plane shutter, but not the kind that move from one side of the frame to the other. The idea is that the top of the image frame gets exposed prior to the bottom of the image frame; while it would work the other way, your egg shapes would go the other direction. Next step is panning, and this is where shutter speed becomes important. To get a regular pan blur effect, with little distortion, I often use 1 over the speed of the vehicle as a guide. Drop the shutter speed even slower, and more blur happens.

Here is an example of a soapbox derby racer, shot using a hand-held Nikon. It is tougher with slower vehicles, because the shutter speed is really slow. This makes it tougher to hand hold and get enough detail. Ideally you would have a tripod that allows panning with the action, but keeps the camera level.

Ciao!

Gordon Moat Photography

**jnantz** · 24-Jan-2010, 14:42

jim

you might need to have your even slower
hold the camera upside down and gravity
will help slow it down below 1/30 ...

good luck!
john

**Jim Galli** · 24-Jan-2010, 17:09

Here's another one. This time the photog obviously wasn't panning as the grandstand is straight.

**Chauncey Walden** · 24-Jan-2010, 18:38

Jim, I played with a few numbers and I don't think your T will have to over exert itself to do this. If you fix your camera position so that the wheel will subtend about 1 inch on your 5x7, my guess is that the T will only have to be doing 12 to 15 mph. No panning required. He was panning in his first pic, but not quite as fast as the car. If you actually measure the travel time of the curtain on the Speed we can figure it out pretty close. I was using 1/5 sec and 6 to 8 inches displacement on the wheel. It varies with your tension setting, of course, and you would want a small slit for shortest exposure. I hate to use shutter speed here as that (travel time) only varies by the tension while the exposure varies by the slit.