Originally posted by NeatKnight Here's another example.
Image A was shot at 1/6000.
Image B was shot at the same time at 1/160 (more than 5 stops brighter!)
Image C is simply image B pulled 4 stops darker in LightRoom. It should be brighter than image A.
So it looks like either:
(a) There's reciprocity failure at high shutter speeds
(b) Camera increases the ISO without permission at high shutter speeds
or (C) The shutter just isn't moving at the nominal speed
How can you come to that conclusion?
Obviously image B is not 5 stops brighter than A. Anyone can see that. The foreground is actually darker. So either the light changed (and just from how the light render, it appears to have done so), and/or you changed the aperture when you changed the shutter time (which the camera will do itself unless you shoot on manual setting).
And C...well given that A and B looks fairly equally exposed, within half a stop or so, of course C will be bloody dark when you pull down the light 4 stops!
Don't take this the wrong way, but I get the feeling you need to read up on the basics of photography. Without understanding how light, iso, shutter speed, and aperture work together, you can't understand anything the camera do.