« Last post by Neutral on August 28, 2015, 05:46:55 PM »
Focus on the A7R II should be accurate, at least for still photos.1. Exactly - as all AF data are provided directly from the sensor and sensor PDAF points.
As for high ISO, its fine if you down sample it to 8mp. Might as well just buy a 8 mp camera though.
There is a very good article on DPR describing the low light autofocus and the issues as well as benefits which depend on the lens you use. Basically, you need to use a F2 or faster lens to get fast low light AF. For f/2.8 and slower, DSLR's may have a accuracy and speed advantage at least in low light.
But it is also important to set focus point to where is exactly required so proper AF mode/AF point selection is critical.
E.g. to focus on eye it is better to use eye AF - this works very well.
To make it easy to use (works almost instantly) the best way is to set AEL button for eye AF and use AF-C mode instead of AF-S.
Then A7rII tracks eye even when face is moving across the frame
2. When DPR published results of this test I did the same tests next day with Canon 85mm F1.2L II and native Zeiss 35 mm F1.4 and had the same results. This was nice surprise.
So I was mentioning this here (AF was functional for brightness level below -6) and in other posts earlier. This ability is basically function of light captured by sensor.
More light in dim conditions coming on sensor - means less noise , more accurate and fast AF.
The only problem with Canon lenses - eye AF is not possible and as well as continuous AF in video mode
Having said that also need to add that AF speed is different for different lenses - e.g. on new 90mm macro it is noticeable slower than on Zeiss 35mm F.1.4 or Sony 55mm F1.8
So far I am pleased with a7rII. Of course it has it's weak points , there is nothing 100% perfect in our world, but in general set of features is very well balanced.