16x9 SD quality

F

frubsen

Member
Not sure where to post this but I have a question regarding 16x9 SD footage and am interested in hearing other people's thoughts.

In the DV world, both 4x3 and 16x9 use the standard 720x480(486 for broadcast) frame size. For 4x3, the pixel aspect ratio is 0.9. For 16x9, the pixel aspect ratio is 1.2. When playing them back you are technically squeezing the video horiztonally to get your 4x3 image and stretching it horizontally to get your 16x9 image.

My question lies here.

Say you had an HD 1920x1080 source. You take that 1080 source, crop the sides off to get a 4x3 image and downconvert it to 720x480.

You take that same original 1080 source and downconvert it to an anamorphic 720x480.

Now both this 4x3 and 16x9 720x480 video have the exact same amount of pixels. However on playback, you squeeze the 4x3 image and stretch the 16x9.

Should the 16x9 image technically not be softer due to the stretching of the image? I thought thought not. I figured the 16x9 image should technically be just as sharp as the 4x3 counterpart since they have been using this method to create dvds for 15 or so odd years.

However in my tests this was not the case. When I downsampled the HD video and played back both the 4x3 and 16x9 SD video, the 4x3 image was actually slightly sharper.

Has anyone else done a test like this and come up with the same or different results? Am I just stating a well known fact here, or am I completely in the wrong here?
 
The vertical resolution is the same for both, but you lose horizontal resolution due to the stretched pixels. I would scale the full 1080 version down to 854x480 EDTV format then squeeze that vertically to 720x480 to get the anamorphic 4:3 for DVD. May help a bit.
 
The question is more about broadcast. Trying to figure out if a 4x3 SD broadcast is sharper than a 16x9 SD broadcast.

The question stem from the news station where I work.

Currently, we shoot, edit, and playback in HD. However our control room and studio is still analog. Analog Production switcher, and analog routing switcher. Graphics, Weather system are all HD but downconverted to analog.
We've been told we won't be HD for at least another year. We've got our hands on a SDI switcher so the question is, if we go the route of 16x9 SD with this new switcher, will it technically look the same as 4x3, or will the image be softer since you are stretching 720x480 pixels to fill the 16x9 frame.

In my tests, I found that the 16x9 was indeed softer which I did not expect.
 
It's not really a valid comparison (apples and oranges) since you're effectively comparing different sources when you crop

Think of it this way: Both have the same 720x480 pixels now, but you have to represent more area from the original source in the 16:9 version in those same pixels. ie. You're only using 1440 of the 1920 pixels in the 4:3 version the way you are testing it now.

You would have to do letterboxed 4:3 DVD for 16:9 content to be a valid comparison, which will make that version much softer. (You're wasting pixels on the letterboxing)

SO if original content was 4:3 , then yes it makes sense to make it 4:3 DVD. Because 16:9 DVD would be pillarboxed (Now you're wasting pixels on the pillarbox). By the same token, if original content was 16:9, then it makes sense to do it the way you were doing it before, because the 4:3 letterbox version will look horrendous
 
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