On Apr 10, 2005, at 4:59 AM, Peter Williams wrote:
We had quite a debate about this way back on the dpreview Minolta talk forum. I initially said that the A2 had a shutter, arguements to the contrary convinced me that there was no shutter. Others said if you look down the lens you can see the shutter, again this was dismissed as being the aperture mech. Further arguement to support the no shutter theory was that the A1 and A2 could do flash synch at full shutter speeds, that is up to 1/4000th sec.
There is no reason to debate this. It is a fact, not an opinion.
The sensor operates in two modes ... one where the image buffer is refreshed under software control without operation of the shutter used for focusing, framing and video capture, and another one which is used with the shutter for still image capture.
You can see the shutter operate quite clearly: Set lens to full telephoto Set exposure to manual Set shutter speed to Bulb Set aperture to wide open Use a penlight with a narrowly focused beam and shine it down the lens Operate the shutter button.
You'll see the shutter close, reopen, close again, then reopen. If you set the aperture to anything other than wide open, you'll also see the operation of the aperture mechanism ... whether the shutter implements the aperture or not I'm not entirely sure, but it is a quite common design in modern leaf shutters used in this sort of camera.
The reason the A2 can perform flash sync at 1/4000 second is that it is a leaf shutter design: there is a point in the operation of a leaf shutter that all blades are fully open at all shutter speeds.
(At 1/4000 second, the total exposure may be less than the time the flash unit's tube is illuminated ... typically you need to pick a sync speed which holds the blades' fully open position for anywhere from 1/250-1/1000 second to obtain the full power of higher powered electronic flash units or studio strobes. For partial power, however, 1/4000 is adequate since most autoflash units have a flash duration range from around 1/250 to 1/10,000 sec.)
Godfrey
