I was invited by Sony USA to try out the latest lenses, cameras and video cameras. They brought us to Jackson WY for a few days of rodeo and landscape shooting.
When you get to be my age you realize the mirror is not always nice to you.
The same thing can happen to the mirror in your camera.
In 1949 the Contax S arrived on the market as the first 35mm camera with a mirror and pentaprism.
It was followed in 1955 with the Japanese Miranda T and the Asahi Pentax. The instant return mirror was a great system and is still in use today.
Tomorrow it might not be.
Sony has introduced two cameras that no longer use the instant return mirror we're used to. The new A33 and A55v have a fixed "Translucent Mirror" where most of the light goes right through the mirror while a little is shaved off and redirected to the auto-focus sensor.
This means the camera can continue to focus in real time, while you're shooting still photos or video. The camera no longer has to predict where the subject will be, but can constantly follow focus a moving subject.
I had a chance to try this out at the Jackson Hole Rodeo. Bull riding and bronco riding are tough for a camera to follow-focus. The animal is charging forward, then spinning, then bucking, then charging forward. The cowboy can't predict it and cameras have trouble as well. I'm not even sure the bull knows where it's headed.
I did most of these shots in the 10-frame per second continuous focus mode using the A55v and the 70-400 F4-5.6 G zoom lens. SAL70400G.
When you're in the 10-frame per second mode, the camera is running the show. It's shooting at the widest aperture it can, is dropping the ISO as low as it can, while keeping the shutter speed high enough to stop the action. Most of these shots were done at ISO 100 at F5.6. I turned the camera off the high speed mode and used the regular continuous motor speed of 6 frames per second for some work. This allowed me to shoot at F8 and a higher ISO and shutter speed. When I looked at the final images on the screen I could only tell them apart by looking at the "info" file.
In either mode the camera is continuously focusing, since the mirror isn't slapping around, and both modes produced sharp, in focus images.
I've shot sports for a lot of years and this is the greatest improvement in auto-focus since Minolta came out with the first working AF camera years ago.