From Firedman Archieves
“Happy now?”, cried the engineers, annoyed that the general public had not acknowledged their tackling of the problem in the first place. “No!” cried the experts (who in hindsight were probably the same people who insisted that Pro cameras don’t have popup flashes). "You can't use MLU in "B" (Bulb) mode when you're taking pictures longer than 30 seconds!"
This standoff lasted for about 2 decades. And now, out of the blue, without warning or explanation, Sony has very quietly added a mirror-lock-up function to the A900, in addition to the 2-second mirror pre-fire on the self-timer. When this mode is invoked, you have to press the shutter release button (either on the camera or via a remote cable) twice to take one picture:
•The first time you press the button, the camera autofocuses, and takes note of the exposure, and flips the mirror up.
•The second time you press the button, the camera takes the picture.
Notice that you have up to 30 seconds to press the button again – after that, the mirror drops down without taking a picture. This is a power-saving feature, for the mirror mechanism uses electromagnets which consume batteries to keep the mirror up.
Is this new feature better than the 2-second mirror-pre-flip of the self-timer? If you use Bulb mode a lot (as do astrophotographers), the answer is "yes". For any other shutter speed of 30 seconds or less, the 2-second self-timer is an easier choice to work with.
"Hey, at least the press will be happy!" says the Sony Marketing guy. (And they would have been, too, had everyone not been distracted with why the .jpg algorithms from the A700 firmware version 4 didn't make it into the A900...)