What went wrong in this racing car shot?

I shot this picure yesterday on the dutch track Zandvoort. The distance to the car was 12m (according to my 10D). The shutter time was 1/350 sec and f-stop 8.0. I shot it with my 24-70 at 40mm. I used the center focus point and had my camera on AI servo.

According to the depth of field calculator, the near limit of acceptable sharpness starts at 5.62 m and ends at infinity. But still the back of the car is sharp and the front is unsharp.

Is it because the car is cornering and the speed of the front is different than the back?
Or did i turn the camera while panning?

Any ideas? What can i do to prevent this from happening again? What are good settings for shots like these?

just need to pan a little faster, the rear 1/4 of the car is sharp, so that is the part of the car where you matched the speed the best. I find it helps to pick a point on the car and then 'aim' at it using one of the focus points. If you can keep the focus point on this point on the car it will produce a sharp image at that point.
Panning for longer before taking the shot will also help you match the cars speed better.

Thanks for your quick response. The picture is actually from a series. I think i managed reasonable to follow the car. The following distances are from the camera:

1st: 24 m
2nd: 12m
3rd: 5.75m
4th: 12m

I notice now that there's something strange. the 2nd and 3rd should be around the same and the 3rd distance is near the 5.62m acceptable sharpness. Could it be that my 10D is too slow to follow the car using AI servo?

Still fairly sure its to do with panning technique. once the car is side on there is a much smaller amount of focusing to do anyway (car is moving less distance away from camera)

You will notice in picture 3 the car is slipping out of the frame. This is probably because your standing on the outside of the bend the panning changes speed as the car gets closer to you. So as it comes into the corner the car will require a faster pan speed than it did previously. Again suggesting panning may be to blame in this case.

The only other thing i find is occasionally when shooting burst that one picture the AI focus will get knocked out by glare etc... the camera will seek, but the shot is still taken. This could possibly produce the type of shot you show. However in my experience will forward focus not back focus.

I am by no means anything more than an amateur, so i may be completely incorrect.

It is because you are panning on the outside of the corner. Stick with me for a minute and allow me to explain.

When you pan from the inside of a corner, the vehicle will not rotate in the frame as it drives around the corner - providing you are stood in the centre of the radius. You could stand in the centre of a circle, the vehicle could drive round and round you, and all you would see is the inside side of it. The view of the vehicle wouldn't change at all.

Imagine being on the outside of a vehicle that is circling. It drives directly towards you, towards you and to the right, just to the right, to the right and away from you, directly away, etc, etc. When you are on the outside of the corner, the vehicle rotates in the frame, albeit only slightly for the time that the shutter is open. The longer the shutter speed, or the faster the vehicle, (more importantly the relationship between them both) the more the rotation will appear in the finished shot.

The sharp part of the frame in your shot, is the point at which the plane of the sensor, is travelling at the same speed, the same direction and in the same plane, as the vehicle. You will notice it is over the back wheel. The blurred part of the car is movement caused by the slight rotation away from the plane of the sensor. Sometimes it is the front wheel, sometimes the middle of the car is sharp, it all depends on which part of the sensor EXACTLY matches the vehicle.

The fact that you have a sharp part in the shot means that you must have been panning at the same speed as the vehicle. You can't have the front of the vehicle traveling faster than the back, or it would stretch into a 7 series half way round the corner! It is the rotation that has caused the motion blur, as everything that happens when the shutter is open is recorded on the sensor.

Hope that helps,

Gary

Im still toying around with panning so I cannot help there. I can however point out the fact that the image is underexposed. I would have bumped up the ISO from 100 to 200 or possibly 400.

Oneslowz28 wrote in post #6258073
Im still toying around with panning so I cannot help there. I can however point out the fact that the image is underexposed. I would have bumped up the ISO from 100 to 200 or possibly 400.

Bumping up the ISO to 200 would narrow the aperture to f11, ISO 400 would give f16. The problem of underexposing has come from the fact that the camera has been fooled into thinking there was more light about from the white car - it was expecting the whole scene to be 18% grey.

There several ways round it, use Manual settings for ISO, shutter and aperture, or take a reading from the background (not including a load of sky) and lock it with the star button on the back of the camera. If all of the cars are white and you know the camera is going to underexpose constantly, you can overexpose 1/3 1/2 2/3 or a full stop (right up to 2 stops on the 40d I think) by rotating the rear command dial. This opens the aperture, if you are in TV, and slows the shutter if you are in AV, allowing more light in to compensate for the camera's missunderstanding of the scene. If you want a certain shutter speed and you reach the max aperture of your lens, then increasing the ISO is the way to brighten the pics because it is unable to open any wider to allow more light in.

fatphotographer wrote in post #6257796
It is because you are panning on the outside of the corner. Stick with me for a minute and allow me to explain.

When you pan from the inside of a corner, the vehicle will not rotate in the frame as it drives around the corner - providing you are stood in the centre of the radius. You could stand in the centre of a circle, the vehicle could drive round and round you, and all you would see is the inside side of it. The view of the vehicle wouldn't change at all.

Imagine being on the outside of a vehicle that is circling. It drives directly towards you, towards you and to the right, just to the right, to the right and away from you, directly away, etc, etc. When you are on the outside of the corner, the vehicle rotates in the frame, albeit only slightly for the time that the shutter is open. The longer the shutter speed, or the faster the vehicle, (more importantly the relationship between them both) the more the rotation will appear in the finished shot.

The sharp part of the frame in your shot, is the point at which the plane of the sensor, is travelling at the same speed, the same direction and in the same plane, as the vehicle. You will notice it is over the back wheel. The blurred part of the car is movement caused by the slight rotation away from the plane of the sensor. Sometimes it is the front wheel, sometimes the middle of the car is sharp, it all depends on which part of the sensor EXACTLY matches the vehicle.

The fact that you have a sharp part in the shot means that you must have been panning at the same speed as the vehicle. You can't have the front of the vehicle traveling faster than the back, or it would stretch into a 7 series half way round the corner! It is the rotation that has caused the motion blur, as everything that happens when the shutter is open is recorded on the sensor.

Hope that helps,

Gary

That makes so much sense now, and for my tiny mind that's saying something. Well done.

just so you know it isnt just you - im new to panning too and got the same result - hope you dont mind me posting... i had a feeling it was due to rotation... but good to get a clear description - thanks...

Everybody is posting partial answers to the issues you are having.

I've written a lengthy explanation on my blog:

http://www.johnthawley​.com …-shot-taking-control.html

fatphotographer wrote in post #6258173
Bumping up the ISO to 200 would narrow the aperture to f11, ISO 400 would give f16. The problem of underexposing has come from the fact that the camera has been fooled into thinking there was more light about from the white car - it was expecting the whole scene to be 18% grey.

There several ways round it, use Manual settings for ISO, shutter and aperture, or take a reading from the background (not including a load of sky) and lock it with the star button on the back of the camera. If all of the cars are white and you know the camera is going to underexpose constantly, you can overexpose 1/3 1/2 2/3 or a full stop (right up to 2 stops on the 40d I think) by rotating the rear command dial. This opens the aperture, if you are in TV, and slows the shutter if you are in AV, allowing more light in to compensate for the camera's missunderstanding of the scene. If you want a certain shutter speed and you reach the max aperture of your lens, then increasing the ISO is the way to brighten the pics because it is unable to open any wider to allow more light in.

I was under the impression that there was no other setting other than manual. In all honesty I set both of my cameras on manual on day one and they have not left it since.

Oneslowz28 wrote in post #6261287
I was under the impression that there was no other setting other than manual. In all honesty I set both of my cameras on manual on day one and they have not left it since.

Sorry, that wasn't advice on your technique. If you look at the EXIF of the original picture, it looks like it was shot in AUTO. Making the ISO higher wouldn't brighten it, it would just add more noise and give a narrower aperture or faster shutter speed.

fatphotographer wrote in post #6263234
Sorry, that wasn't advice on your technique. If you look at the EXIF of the original picture, it looks like it was shot in AUTO. Making the ISO higher wouldn't brighten it, it would just add more noise and give a narrower aperture or faster shutter speed.

Well there is problem 1 right there. Get the camera off of Auto or any of the creative modes and set it to M and never look back. Its not hard to learn to shoot in manual. I promise that you will see a tenfold increase in your keeper rate.

Original date/time: 2008:09:06 15:15:07
Exposure time: 1/350
Shutter speed: 1/350.00
F-stop: 8.0
ISO speed: 100
Focal length: 40.0000
Flash: Not fired
Exposure mode: Auto
White balance: Auto
Orientation: Top-left
Aperture: 6.0000
Exposure bias: 0.0000
Metering mode: Partial

The metering being on partial will also have an adverse affect with brightly coloured cars

Oneslowz28 wrote in post #6261287
I was under the impression that there was no other setting other than manual. In all honesty I set both of my cameras on manual on day one and they have not left it since.

Seriously, and please don't be insulted. BUT... you bought a $4K camera and didn't read the manual?

This isn't difficult stuff... but it does require some effort and a little commitment to the process.

There are a lot of misnomers and frankly, some bad information being posted on this thread.

Panning isn't rocket science. If you think before you shoot, it's pretty easy to figure out. I offered up an entire white paper on my blog. Since you didn't read your manual, I'm guessing you're not going to bother to read my blog either.

If you want to do this and get it right... go read. And, get your head around the fact that it's not just going to "happen." Even though you bought the most expensive camera.

Read: