TeamSpeed wrote in post #17369133
Lenses don't really matter much, similar white balance and exposure (histograms) matter most with ISO comparisons, unless you were looking at detail retention at the same time.
FOV matter a lot, as it dictates how much of the ambient scene is pulled into the background, and what/how much light is pulled into the exposure. [IMAGE'S LINK: https://flic.kr/p/pLqkxe]DSC01746
That said, I dug through my albums, and couldn't find any comparable shots at extremely high ISO's between the 5DIII and a7r. Again, I avoid extremely high ISO's with speed lights and fast aperture lenses, and I don't shoot weddings with two cameras to take comparable (redundant) shots, so I don't really have good comparisons.
Instead, here's a shot at ISO 12,800 that shows that the a7r is plenty capable for wedding photography
by Carlo Alcala
, on Flickr
If you're really interested, I can post some test shots between the 5DIII and a7r. I'm not a fan of these though, and I can tell you anecdotally, that the 5DIII will have less noise than the a7r in really low light, but the difference is not significant enough to really matter.
The initial comment was in response to someone who said that mirrorless cameras won't mean a thing until they can be used for wedding photography, because they don't have the low-light capability of a DSLR. Utter non-sense of course, since they use the same sensors as DSLRs.
Shadowblade wrote in post #17369826
Sensor performance has no bearing on whether the SLR mechanism is obsolete - the same sensor can go into everything from point-and-shoots, to SLRs, to video cameras.
What the SLR system has offered is WYSIWYG image capture as well as fast phase-detection AF. The advent of digital sensors and LCD screens allowed every camera to be WYSIWYG, negating one of the SLR's advantages. Now, on-sensor phase detection obviates the need for a mirror at all and also negates microadjustment errors, since the AF sensor and the image capture sensor will then be in perfect alignment.
The thing is, no-one has actually put a full-size, full-featured AF system into a mirrorless body as yet. That's not to say it can't be done - on-sensor phase detection works the same way and is just as fast as an off-sensor system built in the same way. But mirrorless systems to date have all been about small size rather than performance. Hopefully the next generation, starting with the Sony A9, changes this focus - there's no reason a full-width-and-length (but thinner and lighter due to no mirror box) mirrorless camera with all the same buttons, features and battery power as an SLR, can't perform just as well or even better for capturing action. All they need to do is change the emphasis from small size to maximal performance.
If the a9 hits the market as is currently being speculated (a7r sensor, a6000 AF, in body image stabilization), it would be a legitimate contender to the 5D III.