Hi to every one:

I am new to Canon EOS and I have a question about the 1n-RS. I will like to know which is the effect of the fixed mirror on the lens F stop. If, for example, I use the 85 F/1.2, which will be the resulting F stop due to the light loss ? (because of the fixed mirror).

Any Comments ?

Thanks in advance,

Jorge Saravia

-- Jorge Saravia (1357@mail.usa.com), January 06, 1999

Answers

The RS (and RT) has a 2/3 stop penalty. It's the same as putting a 2/3 stop filter on any lens on any other EOS body. You get the same DOF, but less light at any given f-stop

-- Bob Atkins (bobatkins@hotmail.com), January 07, 1999.

An interesting piece of trivia, often overlooked concerning the 1NRS:

Only 65% of the light passes through the mirror, resulting in about 2/3 stop light loss (compared to the mirror flipped up as with the 1N). But since the EOS 1N mirror passes only 37% of the light, about twice as much light is available for the AF and spot meter sensors behind the INRS mirror. Therefore the INRS specs call for 1 stop "better" sensitivity (AF and spot meter) than the 1N.

-Dave

-- Dave Herzstein (dherzstein@juno.com), April 13, 1999.