Technique questions for John or anyone else...

[Paul George]

...hi all, first post.

John sent me here from fredmiranda.com's forums (my nick is telephono over there). I'm more than a bit of a n00b on some matters of technique specific to shooting cars in motion, but do have a solid grounding in photography generally, so don't worry about dumbing down any terms for me.

In any case, I believe I have panning [at least horizontally] down (click here (http://tenfifteen.net/almslimerock/004.jpg)), but there were a couple of photos from John's work at Lime Rock that brought up questions for me about classes/types of shots that I see somewhat frequently:

Shot # 1, (click here) (http://gallery.johnthawley.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=94404&g2_serialNumber=1)
Just curious how this shot was achieved. EXIF says 1/80s at f20, and while the front portion of the lead FL 911 is sharp as a tack, the track, other cars and the rear-half of the lead car have some sort of pan blur going on. For another example, same sort of thing in this shot (click here). (http://gallery.johnthawley.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=94408&g2_serialNumber=1)

Sorta similar: In this shot (click here) (http://gallery.johnthawley.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=94406&g2_serialNumber=1), the wheels are blurred, and there appears to be a slight 'pan' effect, but it's at 1/250s, so I'm wondering what gives there.

Thanks in advance everyone! To this point (ten years of photography) all my work has been architectural/landscape and speaking events in DC, so this is a whole new thing. Go easy. ;)

[Dustin Finn]

I am not sure I am aware of what shot you are looking at.

The posts here and on the FM forum don't match up.

This is JT's post on this forum
http://community.automotivephoto.net/forums/showthread.php?t=1199

This is JT's post on the FM forum
http://www.fredmiranda.com/forum/topic/552096

Are you looking directly at his gallery ?
I will look there next...

[Paul George]

Sorry--embedded my links to John's gallery, color may be tough to pick up. Let me edit the original post.

[Jim Sykes]

The first shot has blur because all of the different parts of the car and the cars behind are all moving at different angles and speeds in relation to the camera. When you get into slow shutters, the car is moving in a 3D environment, but the camera is putting the image on a 2D plane and therefore you can have different parts of the car moving differently. In this case, the car is rotating in relation to the camera, the front is moving one direction the rear is moving another, so you will only be able to get one part sharp, the front in this case. The cars behind are also moving in a different direction than the nose of the first car and therefore are blurred.

In the second shot, getting down into the 1/250 will still allow for wheels to blur since they are moving so fast on these cars. But it also depends on how fast the car is moving. When shooting at a car coming down the straight, 1/250 is plenty to blur the wheels. Shooting a car in a slow turn will require a slower shutter to blur them. So you have to evaluate what you are shooting and what is going on in the frame and use the most appropriate settings for what you want to achieve.

[Paul George]

Thanks Jim, great info. I guess I didn't really consider the possibility of chassis flex/twist as part of that equation. Do you typically just rattle off several frames per second focused for a given area and then just hope for the best? Or is there some methodical means by which you can effect that sort of shot?

[Jim Sykes]

Its not chassis twist or flex, its just that the car is in three dimensions.

Think about the optics and when you have a car coming at you from a 3/4 view, draw a line from your position to the front and rear of the car. Now move the car forward slightly, you'll see the distance between you and the front of the car changed a different amount than the distance to the back of the car. Now do it again and you'll see the distances changed are different again.

So because of this, when you have a slower shutter, the front and rear of the car are moving at different speeds relative to the lens and therefore you will only get one part of the car in focus.

Same thing above, the car is rotating around a point as it turns. Therefore the parts of the car are moving at different speeds and/or directions in relation to the lens, again causing one part of the car to be in focus at a time. The cars behind the subject car are not in the turn yet and therefore moving in a different direction in relation to the front car, again, causing them to be blurred.

Usually to shoot it, most will grab a couple quick frames because one frame might give you the part you want in focus and another might not.

However, what you need to try to do is focus on the part of the car you want in focus and try to pan on that spot. Just like anything else, you need to move the lens with the spot you want sharp. So if you concentrate on the nose and try to keep the lens constant with it, then you are likely to get that portion of the car in focus. If you judge your pan on the back of the car, that is what you will see sharp.

Here is an extreme example. EXIF is intact if you want to look at it, but its 1/60 shutter. The car is on one of the back straights at Le Mans moving probably 175+ at that point and I'm only 10 feet from the track.

The car is moving by me very fast, the distances between the different parts of the car and my lens are changing at very fast speeds, the front and rear are changing distances at different speeds.

I tried to focus on the nose of the car through the view finder and keep that part panning with my lens. Its hard at that speed and these were a very hit or miss photo.

http://www.speedarena.com/gallery/albums//Sportscar/Le%20Mans/2007/06%20Practice%20and%20Qualifying/027.jpg

Its all physics. At long focal lengths its less exaggerated because the difference in distances arent changing as fast. With a wide angle it changes very fast and is much more exaggerated.

http://www.speedarena.com/gallery/albums//Sportscar/Speed%20GT/2004/05%20Portland/007.jpg

[John Thawley]

Thanks Jim, great info. I guess I didn't really consider the possibility of chassis flex/twist as part of that equation. Do you typically just rattle off several frames per second focused for a given area and then just hope for the best? Or is there some methodical means by which you can effect that sort of shot?

Paul:

Thanks for joining the forum.

Jim is not referring to chassis flex... it's a geometry thing. The baseline of panning is when the subject is perfectly parallel to your lens face. Think of the car attached to a pole that is also attached to your camera. If you stood on one side of a spinning merry go round and photograph a person on the other side... you wouldn't have to pan. Just choose a slow shutter and hold steady... the background would be blurred.

Once the car is NOT parallel to the camera, then there is a speed of travel difference between the front of the car and the back of the car.

Think about spinning a rock on a string over your head. The rock is traveling at a different rate of speed than the different points on the string as you get closer to your hand.

So, with a three quarter / head-on pan, the car is actually pivoting on the plane of the face of your lens. The nose it getting closer while the back is swinging away. So, since only one point can be parallel to the face of your lens, only one point can be sharp. The trick is nailing the spot on the car that you want sharp.

Got a headache yet? LOL

JT

[John Thawley]

Ah... I crosse posted with Jimmy. Good examples.

JT

[Paul George]

OH! I should've read more closely. I gotcha now... great shots btw. I'll give it a go next weekend. Thanks very much for your time.

[Paul George]

Thanks for pointing the forums out to me John, and I cross posted with you too. Makes total sense now, I guess I just read the 'moving at different speeds' portion too quickly. Pretty interesting, and John's 'tele vs. wide' statement helped me get it. Sorta like when you telephoto vs wide-angle a cityscape, the former bringing everything up front and 'flat,' the latter seeming much more three dimensional.

And I'll assume you are auto-focusing (again, forgive my inexperience, I'm used to manual focusing everything at f22 :) ).

[Chris Woolman]

Thanks guys! This was helpful for me as well.

Chris