Focus Question

J

jonhowell

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Took some pictures at Silverstone at the weekend at the Renualt World Series

I got this picture of a Clio, can someone explain why the front of the car seems a little soft but the rest is sharp? Is that just how it is with motorsport and I need to select my focus spot differently or is it my shoddy camera handling?


IMG_6685 by jonhowell2011, on Flickr

Canon 350D
Canon 75-300 Lens
Shutter - 1/50
f11
ISO 200
 
thats an excellent pan, you should be happy with that!
its not so much out of focus as blurry (albeit only slightly).
because its a slow shutter pan, the sharp bits are where they car has hardly moved relative to your sensor whilst the shutter was open. but the extremeties of the car have moved very slightly during the pan, so they arent as sharp.
and of course the background has moved massively across the sensor during the shot, which is why its the most blurry of the lot :)

not sure i've explained that very well, but i can always have another try :)
 
Yeah I think I understand, the back of the car doesn't really move around so much but the front will, maybe from suspension going up and down on the rumble strip and a bit of steering?

I'm very happy with the image as it is only my second real go at panning and I was sat in the top of a grandstand!
 
You should be very happy with that shot, it's excellent. Well done :clap:
 
If you look at the white strip at the bottom of the image you will note that the left hand side of the frame is also softer than the right. (left and right reversed below to show the extreme frame edges next to each other at 200%)

RIGHT SIDE OF FRAME ................................................................. LEFT SIDE OF FRAME
20110823_090907_000.jpg


I could be completely wrong here, but this suggests to me that the problem is not one of focus or movement/bounce of the car, but perhaps most likely the result of a slightly jerky shutter release. If you think about it the image captured at the sensor is reversed. The top of the scene is recorded at the bottom of the sensor. The right side of the scene is recorded on the left side of the sensor etc.. In your image it is the left hand side of the image that is softer. That means it is softer on the right hand side of the sensor - the side where your shutter finger operates. If your grasp of the camera and lens was such that the had the left hand side of the camera anchored superbly, but your press of the shutter button caused a tiny movement on the right side of the camera that might explain it. You could have a tiny rotational movement of the camera pivoting around the solid left side and allowing the right side to pick up some camera shake.

Maybe that's a long shot and complete baloney, but it's a thought that occurred to me. Do you fire single shots or in short bursts? If you fire a burst of maybe five shots perhaps you will get a little camera shake on the first frame or two, a perfect shot in the middle and a dodgy one or two at the end as you prepare to release pressure on the shutter button.
 
The arc the camera is panning at is tighter than the arc of the curve. Whilst you may be tracking the centre of the car at a fairly constant radius, the front and rear of the car may move closer or further away depending on the line the driver is taking.

The effect is magnified by shutter speed, the slower you go the more pronounced it is.
 
Andrew is 100%.

Its basic physics, you can't alter it with any "skill", the effect is simply less or more depending on the exact distance changes and exactly how slow you choose to wind the shutter down.
 
Yep what Andrew says made perfect sense as soon as I read it, at least it isn't me doing something wrong as such
 
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