Sony a7 and Panasonic GX7: Two Cameras sitting on my desk. Must return one.

Started Jan 5, 2014 | Discussions thread
tesilab Veteran Member • Posts: 3,001
Re: Every reply helps... :)

SMD79 wrote:

I thought the a7 had a form of phase detection. Your saying the A Mount lenses with the LEA4 would be faster? That's what someone said before...any tests/sites available that prove that? Just curious.

I don't know that anyone proves it, but you can ask anyone who has tried both. It doesn't require much proof--it's also common sense.

The entire autofocus system from an A55/A57 SLT camera is included inside the LA-EA4 adapter. This is  much different from on-sensor phase detection which has a couple of disadvantages:

1. Phase detection "pixels" on the sensor. Almost all current implementations of PDAF on mirrorless (aside from the Canon 70D) steal a few pixels from the sensor that would ordinarily be dedicated to image data, and are instead performing a phase detection function. I don't think with present technology they can do the job near as well as dedicated PDAF sensors which aren't limited in the same way, since they are not on the image sensor at all. In fact, I believe that in the end, CDAF focusing is still required to fine tune the cruder focus achieved with on sensor PDAF. (In one sense, this is a good thing, since CDAF can provide more accurate results.)

2. The lenses designed for mirrorless cameras are better adapted to CDAF focusing, and generally less well adapted to PDAF focus. (The reverse is also true, which is why an adapter that supports autofocus with SLR lenses cannot acquire focus very quickly.)

 tesilab's gear list:tesilab's gear list
Sony RX1R II Panasonic Lumix DMC-GX8 Sony a7 III Panasonic Leica Summilux DG 25mm F1.4 Sony FE 85mm F1.8 +1 more
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