What's happening here?

Sorry. Yeah that is pretty much what I meant.

Just by watching cars go by with my own eyes I can see the effect. At the right speed I'll see flickering and sometimes even a back and forth motion. I'm not sure why, (although perhaps persistence is a factor), but perhaps simply due to slight changes in angle as the car moves that cause reflections to change and shift slightly. Either way, the effect is perceptible.

I have little doubt that SR enhances or creates the effect where it may otherwise not be visible, but because everything else in the photo appears pretty smoothly blurred, and because the spacing between repeated patterns looks quite large, I would have to says it is simply a reflective strobe effect off the wheel hub.

if the sensor is being moved up and down then it must stop at each extreme and so 'burn' a stronger image onto the sensor at that moment.

Still can' figure it out tho', I'm just going to do it again in the same situation with the SR off. if it continues to do it then my money is on the 'facets of the wheel reflecting more at certain points' theory.

This is a VERY interesting effect that, in a few seconds, asks more questions than my young grandson does. And, as usual not too many good answers come from me.

Is there really a strobe effect on the wheels? Doesn't it look more of a spiral effect for each revolution (8?) of the wheel in the 1/6 of a second exposure and the length of the spiral being the difference of the panning movement in relation to the the speed of the car?

BUT:

- Why do the wheels and other highlights stretch out but the car and driver appear relatively static?

-Why is there an opposite background curvature at the top and the bottom of the photo?

-Why is the car blur horizontally straight while the track of the wheels is curved?

-Why does the track of the front wheel curve in a different arc direction than the track of the rear wheel?


Why, why, why...no kidding a brain teaser! But what ever the reason, this is a VERY interesting photo and there is nothing better than a picture that makes you think. What I think is; "ignoring the bad pan" is likely ignoring the answer.

Regards

Drew

BTW. What was the focal length setting of the 16-45mm lens Darkmonk?

cheaky monkey!
seriously tho' you could be right.

focal length 16mm, I may have been swinging up and down as well as sideways, although the sweep of the greenery seems consistent.
The wheels suggest a twist in the camera as I panned.
Maybe there's twist, vertical movement and hand shake and the SR trying to kick in

I've had similar effects seen on cars, buses etc. BUT, only on slow shutter speeds of ~ 1/15s or slower.

When I've had this the camera was on a tripod with SR off, no panning, just using slow shutter to blur.

not kept any of the images to show the effect though.

I've just taken these to show it's not SR. tripod mounted, SR off, 1/8s, f20, iso 100.

Aj, I think yours is the sun catching each spoke and making a pretty and consistent patern.
I went out again today and took a load of images mostly SR off (no difference) and at different speeds and the slow ones definately show this the best.
I think when you pan smoothly, there is always a part of the wheel (particularly the bottom part attached to the road - not moving up or down or against the direction of the road) that is effectively stationary to the sensor or scribing a smooth image across it.
But because there are several spokes, each arc is burnt onto a slightly different place.
So I think the Spirograph theory wins

... now to PhotoShop a dog into the driving seat.

I don't buy this explanation really.

For the not-panning case, there's no question - a bright bit on the rotating subject will describe the 'Spirograph' shape as we see in JGAR's shots.

If the panning is perfect, the wheel is rotating in the same place on the sensor, so if the exposure is long enough the dark bits will blend to grey with the light bits. If it isn't long enough, the spokes will look like spokes, but blurred.

I'm beginning to think that the original effect is most like the not-panning case, although it looks different enough for me still not to be at all sure.