1.1x Crop on A7s 4K?

If I am not mistaken the A7s has a sensor with 4200 pixels in width, that is what it shoots for stills. However the 4K resolution is 3840 pixels in width. If the A7s outputs 4K at 1:1 scale then it will have a 1.1x crop since it is basically taking a UHD crop from the slightly higher resolution sensor. Shoot a still image and a 4K video at the same time, if they look identical then the A7s is downscaling the whole sensor to 4K, if the video looks cropped comparted to the still then the 4K is a 1:1 pixel crop from the sensor and therefore has a 1.1x crop factor.

I believe the it is a 1:1 pixel crop in 4K but am not sure.
 
^ This
(I haven't had my a7S for almost a year now, but, if I recall correctly, it was like that)
 
https://www.dpreview.com/forums/thread/4059683#forum-post-58415293

I posted this question on another forum (sorry.) If you look at a7sastro's experiment, it looks like the a7s is taking all 4240px width and downsampling to 3840px width for 4k. No crop. Unless the 1.1x crop is so small, you can't see the missing width. @Samuel H are you positive it cropped 1.1x when recording externally?

Wouldn't the same crop happen on the a7s-mkII when recording INTERNALLY since both a7s' share the same sensor?
 
I never used an external recorder with my a7S. And I haven't had it for two years now, so no, I'm not 100% sure it was this way. I still think it cropped a bit when I hit record, but no, I'm not 100% sure.

(I always shoot in M mode, if you use video mode, the crop may happen when you switch to video mode, not when you hit record)
 
Last edited:
Thanks so much @ph2003 & @samuel H for your replies! @ph2003, if you find the time, would you be willing to put the a7s on a tripod, shoot 1080p internally then 4k externally and share a screenshot of both from the a7s?
 
Last edited:
there is no comparison, a7s external 4k quality is very high compare to the internal 1080p, maybe you will not see much difference in a close up shoot, but for wide angle shoot. its night and sky.
 
yea resolution and shapness. is that what you were looking for using an external recording? color vise there is not much difference.
 
No, I was originally curious if the a7s cropped when recording 4K to an external recorder. Given that the sensor is 4240px wide, and UHD4k is 3840px wide (400px difference)

I simply want to know; when externally recording UHD4k, if the A7s crops out 400 pixels of width?

Or does it record all 4240px width and then resize to 3840px width? Thus utilizing the ENTIRE width of the sensor for UHD4K?

Are you able to keep the camera stationary (don't move the camera,) and upload a frame grab from internal 1080p, and a frame grab from external UHD4k?

Thanks so much for all your help!
 
okay so your concern just the cropping, here is 3 frame grab in PP:

external 1080p
ex_1080.jpg
external 2160p
ex_2160.jpg
internal 1080p
in_1080.jpg
 
You must log in or register to reply here.
Back
Top