I had read about a problem encountered when photographing sports events indoors, using very fast shutter speeds to stop the action. The large lights used in many venues can flicker at about 100 times per second, which is faster than the eye can see. But the camera can. Look at this example from a local Nelson gym. Four images taken in a burst lasting less than a second, using a shutter speed of 1/1000:
The second image is not only darker, but the colour is different too. Look at the light in the top left corner to see the culprit.
The gymnast in the background on the bars illustrates the problem very well. Look at these two consecutive shots taken 0.2 seconds apart:
(These shots also show the noise level from the D700 at an ISO of 12800. I wasn’t at all worried about image quality here for these throw-away images, I was concentrating on capturing action shots.)
There is not much that can be done about it, unfortunately. You can read about it in more detail in an excellent article by photgrapher Guy Rhodes in Sportshooter and his test shots here.
In practical terms, it just means that I may need to shoot in RAW at the gymnastic championships, in order to be able to correct the colour balance and exposure afterwards in Lightroom. That means three times the file size, 3x the uploading times and 3x the space requirements on my hard drive. Not usually an issue but at 1000 – 1500 images a day for 5 days it will make a difference.