Saturday, January 3, 2009

Mirror Lockup Returns

This is a historic moment, ladies and gentlemen, for the same marketing team that brought us the lack of a popup flash on the A900 has also brought back the feature that camera engineers have insisted was no longer necessary: The Mirror Lockup Function.


Some history here would be helpful. Back in the 1960’s, SLR shutters were made of cloth and traveled horizontally, and the mirror mechanisms were kind of klunky and loud. If you were doing some delicate macro shooting or astrophotography (or any kind of shooting that required a very steady camera) you were in trouble, for every time you took a picture, that mirror would slap up and the shutter curtain would wizz by, creating internal vibrations that ultimately led to camera shake – even if you were using a tripod! The solution to this was something called the Mirror Lockup Function, and it worked the way its name implies: Once you focused and set your exposure (manually – this was the 1960’s, remember? :-) ), you threw this lever and the mirror was confined to its up position, so that once you took a picture, the major source of internal vibrations had been removed.

In the 1970’s some serious engineering talent attacked the shutter and mirror box design, resulting in a vertically-traversing shutter (thin metal blades instead of cloth) traveling from the top of the frame to the bottom – a much shorter distance. And the mirror mechanism underwent some refinement as well, dampening the action so it didn’t shake like it once did. Yes, compared to the SRT-101 (which handled like a pickup truck), camera shake in cameras like the XD-11 had been reduced by about 95%, making them feel like a Lexus.  (You can see my brief history of Minolta innovation for other interesting camera advancements.)

In the mind of the engineers, the shutter and mirror-box redesign had tackled the internal vibration problem and so the mirror lockup feature started disappearing from cameras. But serious shooters, insisting that lack of a mirror slap was even better than a dampened one, still wanted that feature back. Engineers compromised by re-introducing the feature as a characteristic of the self-timer – that is, when you press the button to use the self-timer, the mirror flips up first, the self-timer starts counting down, and then the shutter finally opens to take the picture. (Hey, 10 seconds should be long enough for the internal vibrations caused by mirror slap to die down, right?) Later versions tied this mirror-pre-flip to a 2-second self-timer, which I personally find very useful.

“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...)

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1 comment:

  1. MLU is much more important on cameras with larger mirrors, like the A900.

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