Why does longer focal length = more skew with rolling shutter?

[Tom Lowe]

I notice that when I get out at like 300mm or 500mm on a camera with a CMOS rolling shutter, the skew is horrendous while trying to pan or tilt. Why is skew worse panning at 300mm than, say, at 24mm?

 

[ericyoung]

Probably because any angular movement is magnified in relative speed across frame. Skew is related to how fast an object appears to move compared to the frame read reset speed.

A pan of say 10 degrees a second on a wide angle doesn't cause an object to wipe from edge to edge of frame very quickly ie it appears to move slowly across frame. At 300mm and above, 10 degrees a second will have objects wiping across the full frame much faster, hence higher perceived skew?

 

[Joe G.]

Biggest Q:

Is this going to be noticeable on the next generation sensors?

 

[Tom Lowe]

Good question. I assume the DSMCs will be much better than any previous CMOS camera in regard to this?