HOW ?? - Streaming lights in background, motion blur object.

[camarosource]

How do they do the following?

You see a night time picture of say the city, and you see the Car lights (usually the red brake lights) STREAMING through the streets?

Or you see a picture with a motion blue of an onject in the background.

IE. http://gmhightechperformance.com/fea...p_z28_12_z.jpg

For example: Perhaps they are taking a picture of a car and in the background a subway goes through and causes the car to be clear but a motion blur of the subway going by??

I know it's all in the exposure timing or something??

[Norm in Fujino]

There are a number of different techniques, all having to do, as you noted, with exposure timing. The camaro picture seems to be merely a brief time exposure (probably not more than 2-3 seconds) from a tripod. The car is still, obviously, while the guys are standing relatively still, yet some of them are moving around enough to cause severe bluring.
The streaming lights in a night city scene is merely the result of leaving the shutter open long enough (10-30 seconds, etc.) to allow cars to drive from one end of the frame to the other. Differing amounts of time produce different amounts of bluring, obviously.
There are also combinations of long exposure and flash, which will create distinct subjects with blurring stretching behind or in front of them. First-curtain flash fires at the instant the shutter opens, whilc last-curtain flash fires just before the shutter closes. Then, if the camera is moving too, it compounds some of the effects.