actual sensor size in 720p/25 at DVinfo.net

Anmol Mishra · April 6th, 2008, 10:35 PM

If I use this camera in 720p mode, does it still use the entire sensor size ? Normally a smaller recording area is achieved by a camera by just cropping off the extra pixels.
So if 1080p is 2M and a 1/2-inch sensor
720p is 1M and only half the sensor is used i.e. 1/4-inch

Is this reasoning correct ?
Just wondering if I am better off with a 720p camera that actually uses all the pixels that it has on the sensor..

Eric Pascarelli · April 6th, 2008, 10:41 PM

720 is scaled from 1080, not cropped.

Both modes use all of the pixels.

You can demonstrate this by setting up a shot and then changing modes. The field of view is identical in all modes. If there were cropping, the 720 modes would have a narrower field of view.

Anmol Mishra · April 6th, 2008, 11:01 PM

I'm just wondering - is 720P better at 35 mbps compression then ? I am still skeptical about HDV..
Is there a study or experiment by EX1 owners about this ?
I am going to shoot a dance film and movement is mentioned as a problem with HDV compression..
So if I shoot 720p at 25fps. It reduces the data rate to 1M resolution. Thus would this be more accurate in terms of compression ?

Eric Pascarelli · April 7th, 2008, 05:29 AM

No question that 720p has lower compression "per pixel."

But as others have mentioned, 1080p makes compression artifacting (especially edge artifacts) smaller relative to the whole image.

In practice, I wouldn't be concerned about HDV style motion artifacting on the EX1 in either mode (as long as it's HQ). XDCAM EX remarkably clean and the codec does not break easily - it's a whole different world from HDV.

The EX1 has almost a 50% advantage in data rate over HDV, and for long GOP codecs, a marginal increase in data rate goes a long way toward reducing compression issues.

Look at the large library of sample footage on this site and you'll see there is nothing to be concerned about, even with lots of motion.

April 6th, 2008, 10:35 PM	#1
Anmol Mishra Major Player Join Date: Jun 2007 Location: Sydney Australia Posts: 401	actual sensor size in 720p/25 If I use this camera in 720p mode, does it still use the entire sensor size ? Normally a smaller recording area is achieved by a camera by just cropping off the extra pixels. So if 1080p is 2M and a 1/2-inch sensor 720p is 1M and only half the sensor is used i.e. 1/4-inch Is this reasoning correct ? Just wondering if I am better off with a 720p camera that actually uses all the pixels that it has on the sensor..

April 6th, 2008, 11:01 PM	#3
Anmol Mishra Major Player Join Date: Jun 2007 Location: Sydney Australia Posts: 401	720p at 35mbps better than 1080p at 35? I'm just wondering - is 720P better at 35 mbps compression then ? I am still skeptical about HDV.. Is there a study or experiment by EX1 owners about this ? I am going to shoot a dance film and movement is mentioned as a problem with HDV compression.. So if I shoot 720p at 25fps. It reduces the data rate to 1M resolution. Thus would this be more accurate in terms of compression ?

April 6th, 2008, 10:41 PM	#2
Eric Pascarelli Major Player Join Date: Nov 2007 Location: Los Angeles, CA Posts: 498	720 is scaled from 1080, not cropped. Both modes use all of the pixels. You can demonstrate this by setting up a shot and then changing modes. The field of view is identical in all modes. If there were cropping, the 720 modes would have a narrower field of view.

April 7th, 2008, 05:29 AM	#4
Eric Pascarelli Major Player Join Date: Nov 2007 Location: Los Angeles, CA Posts: 498	No question that 720p has lower compression "per pixel." But as others have mentioned, 1080p makes compression artifacting (especially edge artifacts) smaller relative to the whole image. In practice, I wouldn't be concerned about HDV style motion artifacting on the EX1 in either mode (as long as it's HQ). XDCAM EX remarkably clean and the codec does not break easily - it's a whole different world from HDV. The EX1 has almost a 50% advantage in data rate over HDV, and for long GOP codecs, a marginal increase in data rate goes a long way toward reducing compression issues. Look at the large library of sample footage on this site and you'll see there is nothing to be concerned about, even with lots of motion.