I have really fallen in love with the Ee-S focusing screen for the Canon 5D. This is not a review in the sense that I will try to cover everything, but it is in the sense that I am sharing my thoughts on Canon’s über-accurate manual focusing screen. I have been using it almost totally in conjunction with Nikon lenses. The why will come later, but I mention it now because using it with Canon or non-Canon lenses is actually quite a different experience, and the answer to this question will make a little more sense with that information in mind.
Basically, the matte screen from Canon is made to manual focus wide aperture prime lenses. Since almost all (if not all) cameras display (in the viewfinder) at about f/2.4ish, the depth of field you see is quite different than the actual depth of field on an 85mm f/1.8, 50mm f/1.4, or some such lens. Meaning, you never really know if you are crystal clear where you want to be crystal clear and you just have to trust that the camera focused right where you wanted it.
Used in conjunction with Canon-manufactured lenses, it works quite wonderfully. I have played with an 85mm f/1.2, which has a such a shallow depth of field that when the pupil is in focus, the eyelashes could be noticeably out of focus. You would be surprised how easy it is to manual focus even this persnickity of a lens with this matte screen. And, to clear up a question I had before buying and using this screen, your auto focus will still work exactly the same: you will have your focus points and the focus speed will be the same as always.
However, using the Ee-S in conjunction with Nikon lenses (or whatever other non-Canon lenses you choose to throw on there) is a very different (and to my eyes preferred) experience. Precisely because the lens and the camera cannot communicate with each other, the camera is basically in constant depth-of-field preview mode. Not only can I see exactly what is in focus, but the brighter the lens the brighter the viewfinder!
A lot of folks whine about needing to focus with the lens wide open and then stop down to the intended shooting aperture. In some situations, that might be necessary, but I still have not done that even one time. If I went to the trouble of using a special focusing screen just so I could use my large aperture lenses, I obviously will tend to need that more open end of my lenses. In other words, I am shooting wide open or close to it most of the time anyway, so it does not matter much.
Additionally, I have found a little trick with this odd setup. I now know that at ISO 100-ish and 1/60th-ish of a second that the brightness I see in the viewfinder is fairly close to the proper exposure. In other words, I do not even bother watching the meter. I simply adjust the ISO and shutter speed (depending on the lighting situation) to where I can use the aperture alone by eye. Meters? We don’t need no stinking meters!
Overall, quirky tricks aside (because I know I am likely the only one who will ever use it that way), the Ee-S matte finish focusing screen makes manual focusing very easy. My one concern initially was that I would really need the speed of auto focus, but with this screen, I have been surprised how quick and successful my manual focusing has been…practically, that is: in the finished photos. My ratio of out of focus photos (because the subject moved or because I just plain missed it) is about the same as before when I was using auto focus. I honestly enjoy being able to focus and compose at the same time instead of focusing then composing.
I give an official barbaric yalp to Canon for the Ee-S focusing screen. My old school, manual focus, eccentric tendencies say thank you. My pocket book says thank you as well, because I can grab cheap, quality glass like the Nikkor 50mm 1.2 for one fourth of the Canon 50mm 1.2! Plus it is smaller, which tickles my low-key fancies. Yalp! Barbaric yalp!