XDCAM progressive modes

[Simon Wyndham]

When the camera first came out there was some information going around that the XDCAM HD was using some sort of trick that lost resolution in order to get progressive scan. However I just found this comment by Clive Cannon over on the NZ Crews website where he said;

"Yes, they are interlace, but associated with each CCD is a DRAM frame memory that allows TRUE progressive readout from the interlace CCDs - clever huh? "

http://www.nzcrews.tv

[Alister Chapman]

I was told that there is no loss of resolution and they used a trick that offset the scans of the G and R/B chips to create the progressive image. My guess is that this process would involve the use of some form of memory buffer, so maybe were both correct.

[Nate Weaver]

I knew about the interlace, because when we did the Texas camera tests we got lower V res readings. so that big hint coupled with the hearsay flying around multiple boards kinda spelled it out.

Not that it matters. They did a great job with it.

If you turn the shutter off in 24p, the V res returns.

[Michael Knight]

What is "V res?"

Michael Knight.

(I'm not embarrassed about asking questions coz I ain't no dummy. My mother just dresses me this way....).

[Nate Weaver]

Vertical resolution.

To clarify even further, the ability to discern, say, a bunch of tightly spaced HORIZONTAL lines. Sometimes people can confuse just what the "vertical" is referring to.

[Simon Wyndham]

Just going to dig this one up again since there was no satisfactory resolve to it.

Nate, did you try the camera in 60i and 30p to see if the same thing happened with the shutter?

[Max Bettelle]

Originally Posted by Alister Chapman

I was told that there is no loss of resolution and they used a trick that offset the scans of the G and R/B chips to create the progressive image. My guess is that this process would involve the use of some form of memory buffer, so maybe were both correct.

You are saying that there is no loss of resolution.... but a progressive picture should be offering a gain of resolution, in comparison with the same interlaced one, don' t you think so?

[Simon Wyndham]

Just had some test shots back from Nigel Cooper. He recreated the shutter on/off test in 25p mode using DSC Labs resolution chart. There is some definite loss of resolution when the shutter is turned on in 25p mode.

Seemingly it isn't progressive scan mode itself that loses resolution. But something definitely happens when you turn the shutter on to 1/50th. Something that you have to do when shooting proscan footage in 25p to avoid motion smeariness.

[Nate Weaver]

Sorry I missed this first time around, but yeah, we definitely saw this at the Texas shootout.

It's not bad enough to make an impact in any real work, though. Non-issue for me.

[Max Bettelle]

Originally Posted by Simon Wyndham

Just had some test shots back from Nigel Cooper. He recreated the shutter on/off test in 25p mode using DSC Labs resolution chart. There is some definite loss of resolution when the shutter is turned on in 25p mode.

Seemingly it isn't progressive scan mode itself that loses resolution. But something definitely happens when you turn the shutter on to 1/50th. Something that you have to do when shooting proscan footage in 25p to avoid motion smeariness.

So i can get the best resolution available in 50i only? And in 25p the best results are with the shutter on to 1/50th or on to 1/25th?