What are the potential advantages in using the RF 70-200 f/2.8 over the recently released EF 70-200 f/2.8 III? Would the AF be faster? I don't get why Canon releases the 70-200 III and then another almost similar version a year later (albeit for the RF system)
At 70mm the back focus is 14mm, so it's native for ML. What are the other advantages?
Firstly the zoom scheme is different from EF. This lens has a variable dimension and for a ML is a great advantage.
Secondly in the patent there also an example for f4 version....
The RF mount is the exact same size as the EF mount. Only the distance between the mount and sensor has been reduced. From what I've read, it does allow elements to be pushed towards the back of the lens, and less elements to be used overall so the lens would technically be lighter.
As to why Canon has not done that, given that they are the master of lenses, I will be more than happy to claim ignorance and simply accept that they most likely know what they're doing.
It‘s about the geometry I think. Solid angle is a lot greater than on the EF-Mount. Thus greater angles are accepted which corresponds to a smaller distance in between the last element and the sensor.
If you were being ironic, then I‘m sorry.
SP is the standard aperture diaphragm. But consider – f/number is focal length divided by aperture diameter. So, a 200mm f/2.8 lens needs a max aperture of ~71mm (200/2.8). Zoom a 70-200mm lens to 70mm, that lens could be f/1.0 (although that's an oversimplification, and even so it would entail all sorts of other optical problems). Regardless, the intent is a constant zoom. A 70mm f/2.8 lens needs a 25mm diameter max aperture, and focal lengths between 200mm and 70mm need max apertures between 71mm and 25mm. The SSP aperture stop creates that effective max aperture to maintain a constant f/2.8 at all focal lengths.
I had the R and the 24-105/4 L on a two-week rental. Primarily, I used it for wildlife, with some landscape and running border collies thrown in.
Much of the wildlife was flying bald eagles, fishing for salmon, and most of the time the lens was the 500/4 Lii, sometimes with the 1.4x and sometimes not. This is a demanding subject, under adverse conditions of cold, wind and low light. The R performed very well, focusing very accurately whenever I did my part of the job well. Sure, a higher frame rate would have been nice, as it would for fast, unpredictable action in sports. But the camera was capable of doing the job. I imagine something will be coming along in the not too distant future which will be more capable for sports and high action.
Before sending the camera back, I took it out for a little torture test. I put the 2xiii on the 100-400 L ii and went to the local duck pond to try get some photos of ducks in flight. I had to bump the ISO up much higher than I would have liked to get a decent shutter speed for something moving as fast as a duck, but the camera was capable of picking up focus and locking on. It was not easy, but then this subject never is, and focus was noticeably slower. But if you prefocused to near the correct distance of the incoming ducks, the camera could pick them up and deliver an in focus photo.
Part of the torture test was the background of the duck pond. It is little aspens, pines and willows--a very dense and busy background. Sasquatch could be napping in there. I chose it because it would be a very difficult situation for the autofocus to work, and work it did. The EVF also worked well. I was surprised, actually. An OVF would still be better in this situation but the R still did the job and is a testament to how good its EVF is. That said, the EVF could still be better, more pixels and faster refresh. Maybe the next generation, a year or two down the road.
I will not be buying the R, but I am impressed. I wanted to see if mirrorless could meet my needs. My only real disappointment was not getting to use it in extreme cold, minus 20 to minus 40, to see if and when the touch interface failed, The coldest I worked with the camera was minus 11F. It worked fine at that temp. If the next RF camera more closely meets my needs, I will be buying.