Canon EOS RT

Press the shutter and the image stays in front of your eye through the entire exposure. No mirror flip, no momentary blindness, just a faint clunk and the frame is gone before you registered any interruption. That is the whole trick of the EOS RT, and it is a strange thing to feel the first time. Canon built this body around a fixed pellicle mirror, a semi-transparent membrane that splits light to the finder and the film at the same time, so nothing has to swing out of the way. The marketed payoff was a release time lag of roughly 8 milliseconds, short enough to matter to sports and press shooters who timed peak action by reflex.

It sits in the EOS family Canon launched in 1987 when they dropped the old FD mount and committed to EF and electronic lens contacts. The RT arrived in 1989 as a special variant of the EOS 630, same body shell, same Canon EF mount, same fast autofocus. What it added was that stationary mirror and the blackout-free finder. The viewfinder is reasonably bright for an autofocus SLR of the era, the command-dial controls are the layout Canon stuck with, and film loading is the motorized auto-thread that takes the manual ritual out of it.

The cost of the pellicle is right there in the physics. Most of the light goes to the film, and only a minority is sent up to your eye. So the film exposure loses about half a stop, but the finder is the part you really notice, because it is running on the smaller slice. In dim rooms it gets dark fast. The membrane is also delicate. It marks if you touch it, it gathers dust you cannot blow off aggressively, and a scratched pellicle is not something you casually replace today.

The shutter is a focal-plane unit running from 30 seconds up near 1/2000, with flash sync around 1/120, which is generous for a body of this vintage and useful when you want daylight fill without dropping to a crawl. Metering is Canon's evaluative system through the lens, and it is genuinely good for color negative work, though even evaluative metering gets fooled by a backlit veil or a white dress against dark wood. When the scene is that contrasty, take a spot reading from the Zone Light Meter app and place the shadows where you want them, then trust your aperture instead of the meter.

These days the RT is a collector's curiosity more than a working tool. People cross-shop it against the plain EOS 630 and wonder why they would pay more for less light, and the answer is the blackout-free finder and the fast release. Street shooters who want to watch the moment land, and anyone fascinated by pellicle bodies, which Canon carried forward into the EOS-1N RS in 1995, are the buyers. Everyone else takes a cheaper 630 and never misses the trick.