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24p hdv v hdcam


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#1 grant mcphee

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Posted 01 March 2007 - 06:10 PM

why is there such a price difference between 24p on pal hdv cameras and 24p on the f900 and the other large format cameras? can it be the same thing? if it is so cheap to do then why was 24p not available on the 750? and will there be any 50hz issues using filming at 24fps? thanks
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#2 Brian Drysdale

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Posted 01 March 2007 - 06:55 PM

why is there such a price difference between 24p on pal hdv cameras and 24p on the f900 and the other large format cameras? can it be the same thing? if it is so cheap to do then why was 24p not available on the 750? and will there be any 50hz issues using filming at 24fps? thanks


I don't think any of the European HDV cameras have 24p, they tend to offer 25p or 50i (The Canon has 25F). The HDV format is a consumer/prosumer format, which is the HD equivalent of MiniDV. Basically one is a mass market, whilst the F900 is a high end camera with less compromises in its design with customers who demand large amounts of backup.

The F 900 has larger number of pixels on it's CCD sensors compared to the HDV cameras and offers 1080p or 1080i together with a range of frame rates. The HDV cameras only offer 1080i or 720p - the latter being offered by JVC (25p). HDCAM has a lot lower compression than HDV, so you'll get less artifacts.

In Europe the HDW 750 is aimed at broadcasters who don't require 24p, they normally only shoot either 25p or 50i. It's a cheaper option than the F900.

The quality of the HD lenses for the F900 or the HDW 750 is much greater than any you'll find on the HDV cameras and that makes a vast difference.

You need to be careful with your shutter speeds if shooting with fluorescents etc and shooting PAL TV sets could cause problems. You'll also need to discuss with the editors regarding any post production difficulties, because in Europe most facilities are more set up for 25 fps than 24fps.

Edited by Brian Drysdale, 01 March 2007 - 06:59 PM.

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#3 grant mcphee

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Posted 01 March 2007 - 07:00 PM

thanks brian,

i'd be interested if you know why the 750 didnt offer 24p like the f900 if it is available on consumer cameras like the canon dv20? Apparently it is 'true 24p' but there must be some catch. can these domestic cameras really offer the same 24p as the high end versions?
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#4 Michael Nash

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Posted 02 March 2007 - 04:00 AM

i'd be interested if you know why the 750 didnt offer 24p like the f900 if it is available on consumer cameras like the canon dv20? Apparently it is 'true 24p' but there must be some catch. can these domestic cameras really offer the same 24p as the high end versions?


There are two main differences at work here:

1) the difference between 24P and 25P;

2) the difference between HDV and HDCAM.

Here's how I understand it (someone please chime in if I'm wrong). The Sony F-900 can record different frame rates by switching frequencies. In coarse terms they are 24 (for 24P), 50 (for 25P and 50i) and 60 (for 30P and 60i). The European 750 model however records only in one frequency: 50. At this speed either 50 interlaced fields or 25 progressive frames can be recorded. Applying this same technology to the US model would mean that the camera would record 60i and 30P. The problem is, there's very little use or demand for 30P. To allow 24P recording with the existing HDCAM technology would mean making the recorder be able to change speeds, which no doubt would drive the price of the product back up.

Canon consumer products don't record a true 24P as far as I know, at least not in any way like the Sony F-900 records 24P (as discrete, non-redundant frames). Canon instead uses a "24F" mode which takes an interlaced signal and de-interlaces it to produce a sort of "faux-progressive" signal, then creates a 3:2 pulldown pattern to spread 24fps over 60i. Add to this that the recording is in the HDV format, which is FAR more compressed than HDCAM. And the Canon is using 1/4" or 1/3" chips (depending on model), compared to the higher-quality, larger 2/3" chips used by the Sony F-900 and 750. And then there's the more sophisticated digital signal processing of the Sony Cinealta cameras.

So with Canon's consumer camera you're not getting the same signal, integrity, or recording pattern as the F-900. And with the fixed frequency of the Sony 750, you couldn't switch between 60i and 24P.

I do think that both JVC and Panasonic are taking a good track with their pro-sumer line though. JVC's 250/251 offers both true 720/24P and 60P, although only to HDV tape at those rates. Panasonic's HVX-200 offers variable frame rates and a better codec, but starting with a lower-resolution chip. Canon's approach isn't necessarily worse but differently weighted, offering a higher resolution interlaced signal in exchange for a compromised 24P, both with the HDV format.
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#5 Brian Drysdale

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Posted 02 March 2007 - 04:43 AM

thanks brian,

i'd be interested if you know why the 750 didnt offer 24p like the f900 if it is available on consumer cameras like the canon dv20? Apparently it is 'true 24p' but there must be some catch. can these domestic cameras really offer the same 24p as the high end versions?


The reason why is market led. Shooting at 25p or 50i, they're aiming the camera at European broadcasters and the HDW 750 is basically a slightly lower spec camera than the F900 (it's not just the format choices), so the purchase price (and rental) is lower.

That's not to say people can't shoot feature films or shorts at 25p, it's been done for years on Super 16 shooting at 25fps.
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#6 grantsmith

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Posted 07 March 2007 - 08:35 AM

I've been reading the article on frame rates in paul wheelers 24p hd book.

He lists 24fps as exactly replicating the cinema projection rate
and then 23.98 as replicating film shot for ntsc where the 3:2 system is used.

How do these systems differ. I would imagine all the hdv consumer cameras use the later version of having 24fps. It seems to be a bit of a cheat to call them true 24fps cameras.
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#7 Brian Drysdale

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Posted 07 March 2007 - 09:50 AM

I've been reading the article on frame rates in paul wheelers 24p hd book.

He lists 24fps as exactly replicating the cinema projection rate
and then 23.98 as replicating film shot for ntsc where the 3:2 system is used.

How do these systems differ. I would imagine all the hdv consumer cameras use the later version of having 24fps. It seems to be a bit of a cheat to call them true 24fps cameras.


In practise, at least in NTSC countries, people shoot at 23.98 fps even for theatrical feature films that will be projected at 24 fps. No one is going to notice the difference and I suspect this may well be within the normal speed tolerances of cinema projectors.

The 3:2 is only applied in post production on the HDCAM cameras like the F900 for TV distribution, so they actually shoot 23.98 progressive. The 24p is actually often more marketing than reality - 23.98P hardly slips off the tongue. The JVC HD 100 series shoots 24p (really 23.98p) HDV without any pulldown. In Europe 25p is normal for television.

The F900 does has the option of 24p fps, but I expect it might be only used in post production facilities in PAL countries that only handle audio for theatrical productions shot on film at 24 fps. I've shot 24p in Europe, however, it's something that has to be discussed with the post people, otherwise you can find yourself in difficulties.

In the USA shooting 23.98p fps is the norm.
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#8 grant mcphee

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Posted 09 March 2007 - 07:11 AM

The JVC HD 100 series shoots 24p (really 23.98p) HDV without any pulldown.



thanks brian.

do you know how this works? I've searched google but could only find info on the pulldown method. I'm assuming that the other 'true 24p' domestic cameras use the same system.


if this is 'true 24p' then, why if it is so cheap was it not used on the ntsc f730 and f750?

it would make sense that it was somehow based on the pulldown method as it is only available for ntsc cameras.


thanks
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#9 Brian Drysdale

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Posted 09 March 2007 - 10:09 AM

thanks brian.

do you know how this works? I've searched google but could only find info on the pulldown method. I'm assuming that the other 'true 24p' domestic cameras use the same system.
if this is 'true 24p' then, why if it is so cheap was it not used on the ntsc f730 and f750?

it would make sense that it was somehow based on the pulldown method as it is only available for ntsc cameras.
thanks


HD isn't NTSC.

The decision as to which frame rates a camera will use the market driven and I expect they didn't want to step on the F900's 24 fps market. The US HDW 730 & HDW 750s are lower priced cameras aimed at broadcasters who don't shoot progressive, while the 24p market is covered by the F900.

The European HDW 750s can shoot both both 25p and 50i, so you find that the broadcaster and productions for broadcast and they tend not to use the F900.

The JVC uses HDV1 (720p), rather than HDV2 (1080i) found on all the interlace consumer/prosumer cameras.

The JVC records the progressive frames.

http://www.jvcpro.co...hdv.pdf?id=6133

The Progressive segmented frame as used by the Sony progressive cameras has a progressive image stored as two separate fields. The fields of the Psf are then combined as one image. On interlace, the fields are not combined, so contain two separate images which are shown one after the other. They don't record a pulldown.
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#10 Michael Nash

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Posted 09 March 2007 - 06:36 PM

if this is 'true 24p' then, why if it is so cheap was it not used on the ntsc f730 and f750?


Because it's not so cheap to have the HDCAM recorder change speeds. The Europen version of the 750 can do 25P or 50i without changing speeds. The US model couldn't do 24 and 60 that way.

And like Brian said, the models are aimed at different markets.
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#11 Brian Drysdale

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Posted 09 March 2007 - 08:09 PM

Because it's not so cheap to have the HDCAM recorder change speeds. The Europen version of the 750 can do 25P or 50i without changing speeds. The US model couldn't do 24 and 60 that way.

And like Brian said, the models are aimed at different markets.


HDCAM records at 77.4mm/s at 24p and 96.7mm/s at 59.94i/29.97p.
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