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shooting 50 frames with hdcam and lightning


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#1 gokay gokulu

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Posted 11 March 2008 - 05:12 AM

hello, i will shoot a film at 50 fps with hdcam, and want to know which cameras i can choose to shoot it,(this will be my first hd experience),this is an professional production so we can hire any of the possible hd's
and my second question is, is there anything that i have to notice about lightning while working hd,and 50 frames,
these are the two examples that our work will be similiar;

http://www.reklamlar...N/P_P/rv/BHEKE/

thanks for your help and advises,
gokay gokulu
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#2 Andrew McCarrick

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Posted 02 June 2008 - 10:35 AM

You can't shoot at 50fps in HDCAM.... the fastest you can get is 30fps... the only thing you can call 50fps on HDCAM is 25fps, which uses a 2:2 pull down to record to 50 interlaced frames (which in all actuality is 25fps.).

Edited by Deleted, 02 June 2008 - 10:36 AM.

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#3 Ollie Bartlett

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Posted 02 June 2008 - 11:28 AM

Hi there,

From what im aware of you cant shoot 50fps on any sony at this present moment, unless you mean 25 frames recorded as 50 interlaced fields.

The closest thing you'll get to 50fps at that level of camera is with the panasonic varicam or HDX900, which can shoot upto 60 progressive fps, but only at 720 resolution. I believe it will give you a 1080i recording, but only via uprezzing the original 720 signal, so not full HD anyway, (although i may be wrong on this), or at least, not the HD youre looking for if youre wanting to use HDCam.

Hope this helps,

Ollie
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#4 John Sprung

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Posted 02 June 2008 - 02:21 PM

The closest thing you'll get to 50fps at that level of camera is with the panasonic varicam or HDX900, which can shoot upto 60 progressive fps, but only at 720 resolution. I believe it will give you a 1080i recording, but only via uprezzing the original 720 signal, so not full HD anyway,

1080i is only 540 lines. They're just arranged in interlaced fields. So, 720p gives you more data to start with, and will produce a better 50 fps image than upconverting from 540 lines with interlace artifacts. Neither is equal to full 1080p, but 720 is definitely more than 540.




-- J.S.
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#5 Ollie Bartlett

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Posted 02 June 2008 - 06:10 PM

jebus! i thought i had it then.

ok so, let me see if i got this...

1080i 50i would be 25 frames, each frame being built up of 2 interlaced fields of 540 lines of vertical resolution each. The first field is scanned lines 1,3,5,7,9 etc, then the second field is scanned as 2,4,6,8,10 etc

1080i 25p would be 25 frames, each frame being 2 interlaced fields, but each field being built up of either the odd or even progressively scanned lines... ie its is scanned 1,2,3,4,5,6,7,8,9,10, but then split into either odd or even field for capture.

720p 25p is simply 25 frames of progressive scanning, ie 1,2,3,4,5,6,7,8,9,10

1080p 25p is the same but with more vertical, and hence more horizontal resolution.

is any of this right? and does that mean that its therefore impossible to get a 1080p 50i signal because the very fact that its recorded progressively means it cannot have been scanned as an interlaced image?

:blink: :blink: :blink: :blink: :blink: :blink: :blink: :blink: :blink: :blink:

Ollie
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#6 John Sprung

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Posted 03 June 2008 - 12:49 PM

...1080i 50i would be 25 frames, ...
...1080i 25p would be ...
720p 25p is simply 25 frames of progressive scanning, ...
1080p 25p is the same but with more vertical, and hence more horizontal resolution.

First, there isn't any meaning that can be attached to "1080i 25p" Something is either interlaced or progressive, or it's progressive but softened for conversion to interlace.

1080i/50 is spoken of as being 25 frames, but in reality they're not quite frames if they were shot on an interlaced camera. The problem is that things can move between the time one field is shot and the next, so putting two consecutive fields together doesn't necessarily produce a picture. If the shot is absolutely static, that works. But if something moves horizontally, its vertical edges get "mouse teeth". If something moves vertically, there can be resolution issues if the rate of motion puts the scan lines on the same parts of it every field.

Another thing you see very commonly in 1080i/50 is material that was shot on film or progressive HD at 24 or 25 frames per second. In making that conversion, each progressive or film frame gets turned into two consecutive fields, so you don't have the "mouse teeth" if you reassemble the right pairs. But the full progressive resolution can't be used in that conversion because you'd get intolerable interline or "small area" flicker. To reduce the flicker to a tolerable level, the vertical resolution has to be filtered down to about 65% of what it is for 1080p. (That's the reason interlace was invented in the first place. In the analog vacuum tube days, it was a way to get 65% of the resolution of progressive, but only using 50% of the bandwidth. In effect, interlace is an analog lossy compression system.)

You can put 1080i that came from film back together into progressive form, but with only 65% of the original resolution.

Given the massive interlaced infrastructure that existed during the development of HD, Sony invented a way to keep using the interlaced gear for progressive. What they call "segmented frame" is full progressive resolution video, just stored on tape in "segments", which are basically just like interlaced fields, only without the resolution reduction.

Back in the analog TV days, it was possible to increase horizontal resolution by improving the bandwidth of the system, but vertical resolution was limited by the number of lines scanned. In digital, that constraint no longer exists. The human visual system sees pictures with mismatched horizontal and vertical resolution has having the lower of the two resolutions, up to a ratio of about 2:1. (More than 2:1, and people see that the tops and bottoms are either softer or sharper than the sides.) So, what we want in a digital system is equal resolution in both directions, aka "square pixels".

1280 x 720 progressive is square, so is 1920 x 1080 progressive. But with 1080i, the 65% limit on the vertical resolution makes the full 1920 wide a waste. That's why original HDCam reduced the horizontal resolution to 1440, or 75%. They could have gone all the way to 65%, but chose to leave a pad in case anybody wanted to live with more flicker to get more resolution.




-- J.S.
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#7 Ollie Bartlett

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Posted 04 June 2008 - 04:23 AM

Right... so when an HDX900 tells me that the system mode is 1080i and the camera mode is 25p, what is essentially happening is that its scannning the image progressively, and then converting the signal into 2 seperate fields to be recorded as an interlace picture (albeit at lower vertical resolution)

Im not sure why this is seemingly so complicated for me :(
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#8 John Sprung

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Posted 04 June 2008 - 12:23 PM

It's complicated for everybody. It's just that some don't realise how complicated it is. They only think they know what's going on. After all, it takes a screen full of text to explain it.

As for the HDX900, It can't produce full 1080p resolution, because the chips are only 1280 x 720. The maximum you can get from those chips is just what you need for 1080i. Doing the math, 65% of 1080 is 702, plenty close enough for TV.



-- J.S.
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#9 Serge Teulon

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Posted 04 June 2008 - 01:39 PM

I can't wait for the day when the HD dust has settled.....
Otherwise we all have to be absolute technical geniuses like our very own John Sprung.
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#10 Andrew McCarrick

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Posted 04 June 2008 - 01:45 PM

I can't wait for the day when the HD dust has settled.....
Otherwise we all have to be absolute technical geniuses like our very own John Sprung.


HD will never settle... we'll just move right past it on to 2k/4k... and thankfully, that's purely progressive with no interlaced formats.
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#11 Robert Tagliaferri

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Posted 05 June 2008 - 03:35 AM

I think I sort of understand some of this (just sort of)... but could someone explain the DVCProHD format 720p60? It's not 60 FRAMES per second, but if it's a progressive format so it can't be 60 interlaced fields, can it?
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#12 Ollie Bartlett

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Posted 05 June 2008 - 03:51 AM

Dont quote me on this, as im proving to be frequently wrong on this subject, but 720p 60 on the DVCProHD format is 60 progressive frames per second, and as far as im aware a camera cant recond progressively and scan in an interlaced way. Im guessing, at its most basic reason, its because of some sort of difference in timing when scanning the vertical lines.

My follow on question (providing of course theres not massive issues with my answer), would be this: Ive been using a HDW-750p for a while now but somehow am only starting to address these progressive / interlace issues properly. Can the 750p record in 1080p? Or is it still a 1080i recording thats scanned 25 times progressively and then split into the corresponding 50 fields for tape?

Cheers,

Ollie

Edited by Ollie Bartlett, 05 June 2008 - 03:52 AM.

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#13 Serge Teulon

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Posted 05 June 2008 - 04:14 AM

HD will never settle... we'll just move right past it on to 2k/4k... and thankfully, that's purely progressive with no interlaced formats.



All the better....lets just get there sooner rather than later and lets just stop fooking around with these pseudo-hd formats!
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#14 Ollie Bartlett

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Posted 05 June 2008 - 04:41 AM

All the better....lets just get there sooner rather than later and lets just stop fooking around with these pseudo-hd formats!


Hang on, hang on... i havnt figured out this one yet.
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#15 Serge Teulon

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Posted 05 June 2008 - 04:43 AM

Hang on, hang on... i havnt figured out this one yet.



What do you mean?
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#16 Ollie Bartlett

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Posted 05 June 2008 - 09:45 AM

What do you mean?


Essentially i mean 'can the industry please hold on for a little while longer whilst i get upto speed on our current brand of HD. Then, when i'm experienced enough with various aspects of 1080 capture, we can all move on to 2k/4k/beyond as one happy family, hand in hand if neccessary.'

Its a big ask i know

(Im joking by the way)
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#17 Serge Teulon

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Posted 05 June 2008 - 12:32 PM

Essentially i mean 'can the industry please hold on for a little while longer whilst i get upto speed on our current brand of HD. Then, when i'm experienced enough with various aspects of 1080 capture, we can all move on to 2k/4k/beyond as one happy family, hand in hand if neccessary.'

Its a big ask i know

(Im joking by the way)


LOL! I suppose it gets like that when trying to take in ALL the different info at the same time.
Just don't get too bogged down by it!
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#18 John Sprung

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Posted 05 June 2008 - 12:46 PM

Dont quote me on this, as im proving to be frequently wrong on this subject, ...


You're right on this one, 720p/60 is in fact 60 progressive frames per second.

Old time tube cameras scanned, but CCD's basically don't scan at all. The best ones are the frame transfer CCD's. They expose the whole frame, then shift the entire image very quickly into a masked part of the chip, identical to the light sensitive part. From there it gets read out into memory while the next frame is exposing. Once it exists as data in memory, you can take it as-is for progressive, or read it out in whatever order you might choose, such as interlace or "segmented frame" in Sony's language for full progressive resolution.

I haven't seen the 750p in person, it's specialized for the 50 Hz markets. It appears to be similar to the 900's, and should shoot progressively, but record in their "segmented" mode. But don't take that as gospel, I could be wrong.




-- J.S.
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#19 Ollie Bartlett

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Posted 06 June 2008 - 05:06 AM

I haven't seen the 750p in person, it's specialized for the 50 Hz markets. It appears to be similar to the 900's, and should shoot progressively, but record in their "segmented" mode. But don't take that as gospel, I could be wrong.
-- J.S.


Just checked it out in the menus and yes youre right... PsF it is. I take it that would be the same path the Varicam or HDX-900 would take aswell when not recording in 720p, albeit that Panansonic would have to call it something else due to Sony's copyright addiction (seriously... you cant copyright 'memory stick'!).

Is there any camera in that sony panasonic bracket (f900/varicam type systems) that can record in true 1080p, or do you need to take the step up to things like the f23, genesis etc? Not that i can get my hands on them but just curious!

Ollie
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#20 Andrew McCarrick

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Posted 06 June 2008 - 01:56 PM

Is there any camera in that sony panasonic bracket (f900/varicam type systems) that can record in true 1080p, or do you need to take the step up to things like the f23, genesis etc? Not that i can get my hands on them but just curious!


HPX3000 ($48k) and HPX3700 (Varicam 3700) ($60k).... both record 1080p with AVCIntra to P2.

Edited by Andrew McCarrick, 06 June 2008 - 01:58 PM.

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