HVX200 PAL : Real 1080 25P ?

K

kuzco

Member
Hi everyone,

I've been reading all posts about the 1080 mode, and I still don't get it...
On the PAL model, is it a true 25 "P" mode ? Or is it just a fake 1080i/50 mode ? Do I really get 25P full images ?

I was planning on doing some editing on the Avid Xpress Pro system. But, il can only handle 1080i/50.
http://www.avid.com/products/xpresspro/featurelist.html

I just want to shoot and edit in a nice 25P mode, but I must be stupid, 'cause I'm lost.
Any help would be appreciated. Thanks !
 
Thanks eliotbaring.

I read that the 25P was carried through a 50i signal (however the two fields were recorded progressively). What difference does it make ? Am I missing something ?
 
Your not missing a lot 8-)

The CCD is an 1080 50p imager. That is, internally it gets an 1080 progressive image from the CCD's( I know, the CCD's are not actually 1080 themselves, but that's a different story...). This signal is the basis of all signals are outputted.

The 1080p25 is a true progressive signal. But it is carried over a 1080i50 signal. This does not degrade the signal. It has something to do with the specs of the 1080 standard.

And nowadays, Avid Xpress Pro handles 1080p25 ( PAL) nicely. Although no 720p50 yet...
 
Thanks eLeventy.

It's more clear now... :-) In fact, the two fields are the same, right ? When you edit your 1080/25P footage in an Avid 1080/50i project, you get a nice 25P ? The think that I didn't get, is that the two fields are identical. Am I right ?
 
Almost!
You right in saying that editing 1080p25 in an Avid 1080i50 project will give you a nice, true progressive image.

But the 2 fields are not identical. You get 1080 of individual lines, which is good. In fact, there are no 2 fields, just 1 frame. If it was an interlaced image, you'd get 540 even lines, and 1/50th of a second later 540 odd lines. If there is any movement in the image, objects appear jagged, because it has moved in that 50th of a second. There are different ways to deinterlace interlaced images, but they all end up blending the two fields, resulting in loss of detail.

If the image is progressive to begin with, you keep all the detail. And you can turn a progressive image easily into an interlaced one, but not vice versa.

Or, in Homer Simpson terms:
Progressive good. Interlace bad.
 
Ok ! I get it... You have one single progressive frame, splitted in two "fields".
Actually, you got 540 lines of your frame, and 1/50th of a second later, you've got the other 540 lines of your frame.
Only, it's the same frame, we're talking about. Nothing has moved, like it would have done in a interlaced image. Right ?

I found this in the operating instructions :


 
kuzco said:
Ok ! I get it... You have one single progressive frame, splitted in two "fields".
Click to expand...
Correct. A full frame imaged at one moment in time. Then it's split into "fields" for purposes of recording; it gets reassembled into a full frame in the edit suite.

Actually, you got 540 lines of your frame, and 1/50th of a second later, you've got the other 540 lines of your frame.
Click to expand...
No. That's how interlaced cameras work, this is specifically not what the HVX is doing.

The HVX images all 1080 lines at once. It just divides it into fields for recording purposes, because the recording format is interlaced.
 
Thanks for your post, Barry.

Barry_Green said:
Correct. A full frame imaged at one moment in time. Then it's split into "fields" for purposes of recording; it gets reassembled into a full frame in the edit suite.
Click to expand...
I finally get it. Yeah !

Barry_Green said:
No. That's how interlaced cameras work, this is specifically not what the HVX is doing.

The HVX images all 1080 lines at once. It just divides it into fields for recording purposes, because the recording format is interlaced.
Click to expand...
Ok. But I still don't get how the frame is divided ?
 
Barry_Green said:
Correct. A full frame imaged at one moment in time. Then it's split into "fields" for purposes of recording; it gets reassembled into a full frame in the edit suite.
Click to expand...
Barry_Green said:
The even lines get recorded as one "field", the odd lines get recorded as the other "field".
Click to expand...
1. Since the two "fields" are getting reassembled into a full frame, in your edit suite, they're always played "together", like one progressive full frame. Right ?
2. So, if odd and even lines are recorded separately, your 1080P image is splitted in two; 540 lines for one field and 540 other lines for the second field. Is this correct ?
 
Yes, but when it's reassembled it's reassembled into a full contiguous frame. Your edit system treats it as individual discrete frames. The "field" issue is merely a temporary transport thing; it's like disassembling your mattebox and rails system to ship your camera on a plane. It gets disassembled and stored for transport, and when you arrive at your destination you reassemble it. Well that's what happens to the 1080/25p frames; they get disassembled into pieces for recording, and reassembled in the editor for working on.
 
What I'm trying to say, is that there's no movement between the two "fields", because they were made from exactly the same progressive full frame. Am I getting this right ?
 
Yes that's absolutely the distinction. Both fields are imaged from the same instant in time, from the same progressive frame. That right there is the distinction between progressive scan and interlace scan.
 
Barry_Green said:
Yes, but when it's reassembled it's reassembled into a full contiguous frame. Your edit system treats it as individual discrete frames. The "field" issue is merely a temporary transport thing; it's like disassembling your mattebox and rails system to ship your camera on a plane. It gets disassembled and stored for transport, and when you arrive at your destination you reassemble it. Well that's what happens to the 1080/25p frames; they get disassembled into pieces for recording, and reassembled in the editor for working on.
Click to expand...
That's a nice explanation. Easy to understand.

Barry_Green said:
Yes that's absolutely the distinction. Both fields are imaged from the same instant in time, from the same progressive frame. That right there is the distinction between progressive scan and interlace scan.
Click to expand...
Great. I finally get it. One last question : when the frame is splitted in two, do you get 540 lines/field ?
 
Thanks for your help, Barry. You made me understand the hole thing.
I will order your book, in a few days, when I'll get my paycheck... ;-) Thanks also to eLeventy and electricpiq.
 
I think I understand why there's a certain loss in resolution when you go to a 25 shutter in 25p recording (in 1080i).

Since 1080i 50 dvcpro hd is interlaced, it can only see 50 fields. The 25p of the HVX does progressive embeded on those 50 fields, right? So theoretically, if you go to 25 shutter speed, you are recording only half fields of the 50 i stream- so it means you are recording half the progressive HVX frames. Can this be correct?

I say this because I shot with the HVX at night and can clearly see a resolution loss when going below 50 shutter. Can anyone confirm this?

I think that's why Panasonic recommends the 50 shuter speed...
 
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