cogitech wrote:
For instance, my 5D tends to overexpose by about 1 stop with my Rokkor 58/1.2 when wide open, so I consistently have my EC set to -1 when using the lens wide open. Throw .73 stops more error into the equation and I would then be consistently stuck at -1.66 EC, which gives me very little room on the low end of the EC scale to compensate for other exposure factors.
I think the fully silvered mirror would tend to make the camera underexpose due to more light going to the metering system. Therefore, if you normally set EC to -1 you would only need to underexpose by one-third of a stop with the new mirror, still giving you almost the whole range of EC still available. However, I do agree that correcting for the fully silvered mirror using the custom function as you suggested would be the best way to handle it.
100% Silver Mirror - done!
At the moment the mirror is glued with tape into place. Want to test that a bit. Probably till I get the change to compare it with a second 5D (have to change there the focusing screen before), hope to get that second 5D in a bit more than a week.
With the EF 50/1.8 at 1.8 (with electronic communication with camera) the camera seems to underexpose ~ 1 EV. But havenīt test that before with normal mirror.
Need the second cam...
Update:
Mirror is inside camera. Works fine so far.
It is only tapped - I want to shave the mirror frame first, and then glue the mirror onto the frame.
With a DIY split screen - from a Canon EOS EF camera - it works, but I think the EE-S screen is even better.
Now: Original 60:40 mirror somewhere in a box.
Instead of it now a 100% reflecting mirror of a manual focus camera taped in the camera frame. Tape makes it reversible, but darken long sides of viewfinder image a bit. And needs sometimes to be tighten.
Mirror needed some grinding before it fits into the frame.
Normal focusing screen is outside in a box, instead of that a focusing screen with split prism of a Canon EOS EF with some parts grind down inside.
Mirror should reflect 2/3 f-stop more light. Not sure about that, and no need to start big measurements efforts. Few measurement indicates about 1 f-stop loss of the original mirror. Probably I measure the mirror again with calibrated optometer instead of Minolta exposure meter.
Future: Grinding / shaving of the mirror frame, that more protruding lenses will be accepted.
Gluing the mirror to the frame.
