Perhaps I’m splitting hairs here a little bit – and I still think the FX6 is an amazing camera. But the more I look at it’s different scan modes and recording mode the more I’ve realised that it’s only actually “Full Frame” in few certain settings. 

When the FX6 is set to UHD and operating from 1 to 60 fps then it’s full frame and the whole width of the sensor is used. Put a Full Frame lens on the camera and you get the same FoV as an FX9 or any other camera with a similar sized sensor.

But if you want to shoot 4K DCI then something strange happens. Switch the FX6 to 4K DCI and the sensor is cropped/windowed by 5% and instead of the field of view becoming 5% wider as happens on most cameras, it instead  becomes 5% narrower. In 4K DCI the FX6 is very slightly less than Full Frame. 

To shoot at more than 60fps the camera has to be in UHD. 60 fps and below it’s full frame but when you go above 60fps the image is cropped even more, this time by 10% so the FoV gets 10% narrower.

If you want to record UHD Raw at any frame rate the image is also cropped by 10% so UHD with raw out at 30fps results in a 10% narrower FoV than when you are not outputting raw. When you enable raw at 4K DCI raw it’s a 5% crop.

So while none of these crops are huge it is worth noting that the FX6 is actually a little less than full frame more often than not!

Just to put all this into some perspective the FX9’s Full Frame Crop 5K mode involves a 17% crop. The FX6 outputting UHD raw or recording UHD at more than 60fps is a 10% crop. That’s not a vast difference. In these modes the FX6 is closer to the FX9 5K mode than to Full Frame.

Why is this? Well the FX6’s sensor is 4.2K pixels across. In the “normal” UHD frame rates (up to 60fps) the full 4.2K is read and downscaled on the fly to 3840 x 2160 UHD.  When you shoot 4K DCI there is no downscale and instead the sensor is read out at 4K and the extra 0.2K of pixels at the edges of the frame are not used – 0.2K being 5% of 4.2K and thus you have a 5% crop and the FoV becomes 5% narrower in DCI 4K than in UHD.

When you shoot above 60 fps then the sensor is read directly at 3840 pixels rather than 4.2K to make the readout simpler and faster. So now we are reading 0.4K fewer pixels from the sides of the sensor which is 10% of the total pixels and we get a 10% narrower FoV above 60fps as a result.

As I said at the start, perhaps I’m splitting hairs. I certainly don’t think this detracts from the FX6 in any significant way. But if it’s a camera you are thinking of getting, you should be aware of this.