Is the Native Size 720p or 1080p

DavidNJ

DavidNJ

Carbonite Member
The HVX200, HPX170, and HMC 150 have three 960x540 sensors, with the green sensor offset half a pixel.

Does that make the native resolution after initial processing 1080p? Is there a second process to down scale it to 720p?

Curious...if there is it would add a second interpolation to add artifacts. On the HMC150 the recording bandwidth is fixed, so there is a tradeoff in additional compression. However, on the DVCProHD systems the compression is fixed and the bandwidth varies.

Does 720p add extra artifacts?
 
The system samples the analog signal off of the chips into a 1920x1080 digital frame. The chips are not digital, they're CCDs which are analog. So the system samples them in the initial A/D process into a 1920x1080 matrix.

All internal processing is conducted at 1920x1080.

If you put the cam in 720p mode, it'll downconvert before recording.

For answers to whether there's artifacts or not, no, the 720 is excellent, and you should judge it based on the footage.
 
Ok...has someone shot and posted a detailed still life (testing the down scaling and not the compression) in 720 and 1080 (speed doesn't matter since DVCProHD is recorded in a fixed bandwidth per frame regardless of frame rate.
 
Barry, do you remember where those were? Actually, for this charts won't do it. It isn't resolution...it requires a complex color image that challenges the scaling interpolation. You would need one of those multiple overlapping sine wave ring charts. A capture would allow a blow up of all sorts of detail.
 
I don't know how you'd intend to isolate it though. I mean, 1080 mode scales down to 1280x1080. 720 mode scales down to 960x720. So do you plan on evaluating the anamorphic images?

It would probably be better to use a 150 for this, because on the 150 it stores the native raster so there's no pre-filtering going on in the codec. And a still-life should eliminate any GoP issues, meaning that 1080/24p and 720/24p on a still frame, in 21mbps mode, should deliver on par with the best codecs out there (except for the 4:2:0 color sampling).
 
You are correct. This test may only work with HD-SDI output. The HPX170 has a constant compression, but down scales all images. The HMC150 maintains the image size, but has a constant data rate causing more compression at 1080p.
 
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