This is what happens when a photo is taken on a Nikon D3.
A series of events happen:
- The mirror is raised, and at the same time the aperture of the lens is adjusted according to the camera’s settings (f/16).
- The shutter moves across the image sensor. At 1/4000, you can see that the shutter moves to expose a small slit of light to the sensor only. A slit is produced because at such high speeds (1/4000), the rear curtain must start moving before the front curtain completely exposes the image sensor. This is why normal flash sync will not work. If you use normal flash sync at such speeds, you will get photos like these.
- After the rear curtain has traveled across the image sensor, the mirror starts to go down, and at the same time the aperture of the lens is opened up to maximum (f/1.4 in this case).
- The camera is now ready for another shot.
At normal speeds the mirror and shutter action is almost impossible to study. Also because of the high speed operation, the shutter and mirror mechanism must be well engineered to last long. A high end camera’s shutter can usually last for about 100,000-150,000 actuations.