No precision focus screen for 5D Mark iii

Why did Canon decide their customers no longer need nor want a precision focusing screen (eg-s) with the 5D Mark III?

Because of the fancy LCD overlay, which stops you from changing the screen. This was first introduced on the original 7D, and has spread across the higher range cameras as they have been upgraded.

Alan

BigAl007 wrote in post #17713775
Because of the fancy LCD overlay, which stops you from changing the screen. This was first introduced on the original 7D, and has spread across the higher range cameras as they have been upgraded.

Alan

Then how do you explain the interchangeable screens in the 1DX with it's overlaid LCD?

The introduction of Liveview has reduced the need for precision "optical" screens. What seems to be more important nowadays is a bright, clear viewfinder that has little tooth to the screen.

With the AF system of the 5D3, I don't miss a focus screen option. When I had the 5Dc, I liked having a 3rd party split prism screen to be able to manually confirm focus. If you're really determined, it is possible to change screens with the 5D3 (but can void your warranty then).

Does swapping the focusing screen throw off the lens calibration? I'd hate to recalibrate all my lenses twice.

BigAl007 wrote in post #17713775
Because of the fancy LCD overlay, which stops you from changing the screen. This was first introduced on the original 7D, and has spread across the higher range cameras as they have been upgraded.

Alan

Except the 7D II and the 1DX both have similar LCD overlays to the 5DIII, and both support super precision matte focus screens. I'll bet when the 5D Mark IV is released Canon will go back to supporting it.

Not sure. My 5Dc didn't have micro adjustment, and I used the split prism for MF. I would assume there wouldn't be a difference since the phase detect is happening under the mirror. I didn't notice much difference with AF, but there can be a slight difference with metering. The 5Dc had a menu setting for selecting a precision focus screen (to adjust for the difference in opacity EV). Since my focus screen was 3rd party, I tried selecting the closest equivalent. Since the 5D3 doesn't have that menu setting, would assume that metering might be the main thing affected.

No, the AF mechanism is at the bottom of the camera behind the half-silvered reflex mirror, so swapping focusing screen has nothing to do with nothing except if the viewfinder is fuzzy to your eye because the focusing screen is not properly in place.

Wilt wrote in post #17719655
No, the AF mechanism is at the bottom of the camera behind the half-silvered reflex mirror, so swapping focusing screen has nothing to do with nothing except if the viewfinder is fuzzy to your eye because the focusing screen is not properly in place.

And where is the auto-exposure eye? Behind the mirror, as well?

The AF "eye" (phase detect sensors) are at the bottom of the mirror box. That's what Wilt was referring to. The way AF works on a DSLR....light goes through the lens and gets reflected up to the viewfinder by the mirror. The meter is on the top around the pentaprism. Behind the main mirror, there's a secondary mirror that's angled seperately, and directs light from the lens down to the bottom of the camera (hitting the phase sensor/ AF system). Because the meter is up in the pentaprism area, it's the main thing that would be effected by changing focusing screens. So with "exposure eye", I would assume you're meaning meter (which is in the pentaprism). There's just one meter...it's a sensor that lets the camera measure available light. The "auto" modes are all determined by the camera's processors (that are deep inside the camera).

davesrose wrote in post #17720848
The meter is on the top around the pentaprism.
. . . directs light from the lens down to the bottom of the camera (hitting the phase sensor/ AF system).

Uhh? Are you saying the pentaprism is between the eyepiece and the focusing screen? The pentaprims does the auto-exposure, yes?
Also, if the AF eye is behind the mirror, how does light pass through the mirror?

Well actually, the cheaper DSLRs don't have "pentaprisms"...but I was trying to be simple. Some DSLRs don't have a traditional "pentaprism", but a series of mirrors that reflect light from the lens on up to the viewfinder (and also flips the image right side up). Higher end DSLRs (and traditional SLRs) have a glass prism (pentaprism) that bounces light to the viewfinder. A pentaprism isn't a sensor...it's the way light gets to the viewfinder. The meter is what's detecting light and letting the camera decide how to expose.

With the AF, there's a secondary mirror under the primary one. There's an area of the mirror that's semi-transparent to allow light through to get reflected to the phase detect mirror. The phase detect mirror then reflects light to two or more sensors. The camera will keep focusing until the *stereo* image lines up with the AF sensors.

Here's an article on DSLR AF:

link