A7s ii 120fps and crop factor. Explanations please?

[xbiron]

Hello

I'm thinking about switching from my LUMIX G7 micro 4/3 to a full frame system, the A7s ii.

But I discovered that the 120fps mode has a 2.2x crop factor. Is it really true? I can't understand why such a great camera would have such a big huge factor.

I want to switch form m4/3 system because of the 2x crop factor and get a thinner DOF, and wide angles. But this spec kills me.

Can somebody explains me why there is a 2.2 crop factor? And does it affect the DOF like a small sensor does? Thank you.

[VTC]

Place an APS-C lens on the camera institutes a 1.5x crop factor. Running 120fps on the 4K sensor takes it to HD with a 2.2x crop factor to maintain image quality. Depending on what the shoot is and the final product use is I forego using 4K and instead roll HD because there's less rolling shutter evident in the HD as opposed to the 4K in especially animated shoots. An external recorder gives me the option of using HD if the internal 4K turns to Jello at times.

[bennytan]

Hey xbiron,

 

My thoughts are the a7S' processor isn't fast enough to handle a full-sensor readout at full frame, UHD 4K at 120fps, which is why the camera goes into windowed mode and only activates the centre 1920x1080 portion of the frame.

 

Yes, at cropped sensor mode, you will have the look of a cropped sensor, which is similar to MFT. There is no way around that. On Sony's cine cameras, like F55, you're able to switch between pixel-binned (full sensor-size) and centre scan modes, but it doesn't seem like Sony has left that as an option for the a7S II.

 

There's a lot you can do with the G7's sensor to achieve a shallow DOF. If you're already invested into the MFT system, why not consider the GH5?

[xbiron]

Hi Benny,

 

Thanks for your answer. Too bad the 120 fps is cropped. As you said, it must be a processor matter. For me it's kind of a deal breaker. And I might be considered the GH5 options. Thank you for your time.

By the way, I visited your website. I'm really impressed by your work. Congratulations.

 

Xavier.

[bennytan]

Hi Benny,

 

Thanks for your answer. Too bad the 120 fps is cropped. As you said, it must be a processor matter. For me it's kind of a deal breaker. And I might be considered the GH5 options. Thank you for your time.

By the way, I visited your website. I'm really impressed by your work. Congratulations.

 

Xavier.

 

Hey Xavier,

 

Thanks for the comments! The A99II from what I understand is able to shoot at 120fps with a full sensor readout, but you have another issue of having to invest into the diminishing A-mount.

 

One more thing that came to mind would be to use a Metabones Speedbooster to kind of offset the 2x crop of shooting 120fps on the a7SII. It seems like Sony is on the way to offer a full sensor readout at 120fps on the next a7S III if you're willing to hold out for that.

 

Personally I'm not a fan of the GH5 and the ergonomics and interface alone turned me away from the GHx line, but each to their own.