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Kickstart
3rd of October 2006 (Tue), 18:30
Hi

Tried a few shots a few weeks back with fairly slow shutter speeds. For example:-

http://www.alfa-pages.co.uk/TempPicture/Kjw_4411.jpg

The effect is nice. However, what exactly causes this effect?

The bike has moved something like 2 foot while the shutter is open. The front of the fairing is sharp, but the further from that point the less sharp it is. Fairly small aperture so not a depth of field issue. Not camera shake as if so the front would not be sharp.

Just trying to get my head round how this happens, so that I can control it more.

All the best

Keith

KennyG
3rd of October 2006 (Tue), 18:45
Distance relative to the focal plane means the camera "sees" the rear of the bike travelling at a different speed to the front.

Kickstart
3rd of October 2006 (Tue), 19:03
Hi

Not sure how that affects it. Would think that the focus is determined by the distance and that is barely different between the front and the back. Or do you mean that as you pan the angle is changeing, effectively getting longer (added to getting larger as it gets closer).

Sorry, just struggling to work it out.

All the best

Keith

vwpilot
3rd of October 2006 (Tue), 21:25
The different parts of the subject are moving at different speeds relative to the camera. So in this case the camera panned perfectly with the front of the bike, but the back moved a bit while the shutter was open causing motion blur.

It will always happen unless the subject is moving exactly perpendicular to the camera and at that instant everything is frozen in relation to the camera. Anything that 3/4s will have different parts moving at different speeds, then depending on focal length and shutter speed, some shots will have more or less blur.

John Thawley
3rd of October 2006 (Tue), 21:47
Hi

Not sure how that affects it. Would think that the focus is determined by the distance and that is barely different between the front and the back. Or do you mean that as you pan the angle is changeing, effectively getting longer (added to getting larger as it gets closer).

Sorry, just struggling to work it out.

All the best

Keith

It's nothing to do with focus. It's the difference between the speed of the subject vs. the speed/motion of your pan.

Consider the only thing truly in sync with your camera motion is the part of your subject that is travelling exactly on the plane of your lens face. Since the front of your subject is travelling faster than the rear, you're in essence trying to shoot and pan two distinctly different objects... at least as far as the panning motion goes.

Even though your subject is not at an extreme angle coming across the plane of your lens face, you still need to consider that your pan is actually an arc. Even had the bike been absolutely parallel to your shooting position and dead in front of you, your panning "arc" would still show up as a bit blurred/soft on the ends when using a slower shutter.

A good example of the geometry is an old record player and 12" vinyl record. When the tone arm / stylus travel across the record from the outside to the inside, there are only two intersections where the needle is at an absolute perfect tracking postion sitting inside the record grooves. The rest of the time the needle is actually skewed to the sides of the grooves.

It's geometry. The task at hand for the photographer is to make this work for the composition. The angel of your subject is a bit weak... hence the blur is not really adding anything to the image. I think that might be what is frustrating you.

Here are a couple extreme examples that (I think) make it work to tell a story:

http://community.automotivephoto.net/photopost/data/503/IMG_0961_a.jpg

http://gallery.johnthawley.com/albums/albup54/aaa.jpg

JT

Kickstart
4th of October 2006 (Wed), 07:12
Hi

Thankyou. Think I get it now.

Any tips for how to control it more. For example in the above shot I was using the central focus point(I think), but somewho managed to get the nose as the sharp point. Happy in this case, just a pain when I land up with the tail in focus!

As an aside, if using AI Servo, does the lense adjust focus while the shutter is open predicting where the target is on a long exposure?

All the best

Keith

John Thawley
4th of October 2006 (Wed), 10:58
Hi

Thankyou. Think I get it now.

Any tips for how to control it more. For example in the above shot I was using the central focus point(I think), but somewho managed to get the nose as the sharp point. Happy in this case, just a pain when I land up with the tail in focus!

As an aside, if using AI Servo, does the lense adjust focus while the shutter is open predicting where the target is on a long exposure?

All the best

Keith


Control? You want control? LOL

The slower you drop that shutter, the less control you'll have. Look... Tiger Woods doesn't shoot holes-in-one everytime he goes on the course. But, I'm guessing his chances are better than yours or mine.

So... all you can do is work on improving your chances.

First step is shot selection. With the example you posted, you were pretty much staged for a lack-luster result. The bike is not coming straight past you nor is it at much of an angle. So... it's destined to be a weak shot.

Speaking strictly to slow shutters, two conditions can help create an exciting effect. First is having the subject passing absolutely parallel to the lens and nailing it right dead center (on the subject.) If you do this with the car nicely set to the back and low in the frame, you'll get a nice streaked background and a very racey looking shot.

When the subject is approaching at a steeper angle, the closer it gets to you, the less control you'll have. Any time your body motion is to fast, you'll be jerky and not smooth. So it will require the right focal length lens, keeping the car further away and then a nice quick smooth pan. Getting the nose is the tough part... but you will increase the chance is the car is further away... as its relative speed to your postion is slower. As it gets closer, it's faster.

I "try" to get my focus point a little further back from the nose and across the car. So if I'm shooting from driver's left, (US) I'm going to aim almost at the passenger side of the windsheild

Again... all this can do is increase your chances. The keeper rate on slow pans decreases more as you lower the shutter speed.

Here are couple slow angles shot at dusk... one catching the nose.. the other catching the number plate. I like both... other's have a preference.



http://community.automotivephoto.net/photopost/data/500/Thaw_28231.jpg

http://community.automotivephoto.net/photopost/data/500/Thaw_28249.jpg

This is a dead on side pan at 1/60

http://gallery.johnthawley.com/albums/albup52/abe.jpg

JT

Kickstart
4th of October 2006 (Wed), 12:09
Hi

Well, enough control to get the effect I want with less luck required.

Shot wise I do actually like the shot of the bike. Only reason I was playing at that point was because of a hump in the track which the quick people wheelied off. The slow ones just looked boring so I started to turn the shutter speed down(~1/60th, bikes were doing 120+mph at that point).

Interesting you track aimed at almost the far corner. However given a slow shutter speed and therefore probably a fairly small aperture, how important is the focus point? Or if I am understanding peoples comments correctly is it the point that it tracked perfectly that is more important.

All the best

Keith

John Thawley
4th of October 2006 (Wed), 20:16
Hi

Well, enough control to get the effect I want with less luck required.

Shot wise I do actually like the shot of the bike. Only reason I was playing at that point was because of a hump in the track which the quick people wheelied off. The slow ones just looked boring so I started to turn the shutter speed down(~1/60th, bikes were doing 120+mph at that point).

Interesting you track aimed at almost the far corner. However given a slow shutter speed and therefore probably a fairly small aperture, how important is the focus point? Or if I am understanding peoples comments correctly is it the point that it tracked perfectly that is more important.

All the best

Keith

You're spot on. It's all about tracking. Depth of field went out the window several stops back. :)

Deciding where you need to track to get what you want tracked becomes the trial and error part. Everything is coming toward you "wrong." So... you just have to feel your way.

My theory is, it's not a shot you're going to do or use all the time. Even if you could nail it every time, you'd only want to sprinkle it around your portfolio. So... fire away. Shoot till you see one you like.

JT

Kickstart
5th of October 2006 (Thu), 16:37
Hi

Thanks. Any suggestions for tracking like this (short of buying an old EOS1 RS)?

Might just set aside a day to wander along and try some slow shutter speeds accepting a 90% failure rate.

All the best

Keith

creamcorn
17th of October 2006 (Tue), 01:46
Hi

Thanks. Any suggestions for tracking like this (short of buying an old EOS1 RS)?

Might just set aside a day to wander along and try some slow shutter speeds accepting a 90% failure rate.

All the best

Keith

Why bother learning to pan when so many people on this site have made a living out of shooting cars head-on?