A7SII Aliasing in 1080 50p at DVinfo.net

Chris Stevens · March 10th, 2016, 03:28 AM

When shooting 1080 25p there is very little aliasing in the image, however switch to 50p and there is noticeable aliasing. Why should this be? The frame size is the same... Would a separate recorder be the answer? In other words is it a bitrate issue?

Chris Harding · March 10th, 2016, 07:56 AM

Hi Chris

With my EA-50's I used to get it really bad at 50P but clean at 25P ... it has been said that 50P needs a minimum bitrate of 50mbps to give a clean image so I used to shoot in 25P which is less taxing on the codec. It was also worse in the AVCHD codec too ..On my Pannys I can shoot in MP4 with no issues but in AVCHD on the Sony I used to get problems as well with pixellation and even posterization issues on overexposed portions of the image ... Do you have to shoot at 50P??? Does the A7S have other formats you can use ..might be worth testing them??

Noa Put · March 10th, 2016, 08:27 AM

As I recall that pixelation problem was because of a certain preset that was used, I don't remember having any issues with 25p vs 50p on my nex-ea50 though.

Quote:

however switch to 50p and there is noticeable aliasing

I don't have a answer to that but had a similar problem on my panasonic g6, when I shot at 25p it looked exactly the same as my gh3, but as soon as I switched to 50p the image became softer. It was up until I shot a resolution card that I could see the resolution drop as soon as I switched to 50p and all other settings where the same, my gh3 did not have that problem. Never found out what the issue was.

Khoi Pham · March 10th, 2016, 03:41 PM

It is like that with Sony A7s also.

Ivan Mosny · March 14th, 2016, 12:38 PM

There is no enough speed/power/cooling to make full pixel readout at 50P by full frame. So there is line skipping like in other cameras. You can have very clean 50P i APS-C mode.

March 10th, 2016, 03:28 AM	#1
Chris Stevens Regular Crew Join Date: May 2007 Location: UK Posts: 44	A7SII Aliasing in 1080 50p When shooting 1080 25p there is very little aliasing in the image, however switch to 50p and there is noticeable aliasing. Why should this be? The frame size is the same... Would a separate recorder be the answer? In other words is it a bitrate issue?

March 10th, 2016, 07:56 AM	#2
Chris Harding Inner Circle Join Date: Jul 2009 Location: Perth, Western Australia Posts: 8,441	Re: A7SII Aliasing in 1080 50p Hi Chris With my EA-50's I used to get it really bad at 50P but clean at 25P ... it has been said that 50P needs a minimum bitrate of 50mbps to give a clean image so I used to shoot in 25P which is less taxing on the codec. It was also worse in the AVCHD codec too ..On my Pannys I can shoot in MP4 with no issues but in AVCHD on the Sony I used to get problems as well with pixellation and even posterization issues on overexposed portions of the image ... Do you have to shoot at 50P??? Does the A7S have other formats you can use ..might be worth testing them??

March 10th, 2016, 03:41 PM	#4
Khoi Pham Major Player Join Date: Nov 2004 Location: Dallas Posts: 747	Re: A7SII Aliasing in 1080 50p It is like that with Sony A7s also. __________________ Khoi Pham www.proeditproductions.com

March 14th, 2016, 12:38 PM	#5
Ivan Mosny Regular Crew Join Date: Sep 2007 Location: Poland Posts: 141	Re: A7SII Aliasing in 1080 50p There is no enough speed/power/cooling to make full pixel readout at 50P by full frame. So there is line skipping like in other cameras. You can have very clean 50P i APS-C mode.