bjyoder wrote in post #10769637
Wouldn't the point of a pellicle mirror be to show a TTL view through the viewfinder? Why would they go through the trouble just for the AF?
The point of a pellicle mirror is shorter shutter lag, no VF blackout, potentially faster framerates (no longer an issue), and a continuous "feed" to the AF sensor.
In a "normal" mirror system, there is a blackout for both the AF sensor and the VF when the mirror flips up. By leaving the mirror fixed, the AF sensor has continuous information and requires less guesswork in predictive AF (AI Servo).
Since the mirror doesn't have to flip up, this also decreases shutter lag, and the frame rate is theoretically limited by how fast the shutter curtains can be moved, not the mirror. Point is moot, though, since Sony's pellicle design can't do more than 10 fps anyway, which is more than possible with a moving mirror. But a moving-mirror system is limited to about 10fps (I think Nikon got to 12) because the AF sensor isn't given enough time to get new data if the framerate is much faster.
Also, I don't think much more than 10fps is possible even with a pellicle mirror...otherwise Sony would have done it, and Canon wouldn't have stopped with the 1N RS. But they did, because the 1v got 10fps perfectly fine with a normal mirror.
And - something I just thought of - you'd still have blackout while the shutter is moving across the sensor to make the exposure, hence defeating the pellicle mirror again.
Sure, but 2ms (at 1/500) is better than 80...
The problem is light loss, EVF lag, and the same frame rate as a "normal" mirror.
edit: mirror slap is another problem with "normal" mirrors...but that's not an issue when shooting action.