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HD, SD, Film and compression


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#1 Jason Outenreath

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Posted 20 August 2008 - 02:44 AM

I'm always a little intimidated posting, since there are so many great minds here, but I have a few (hopefully) quick questions...

Is there any point in shooting on HD if in the end you can only output to miniDV or DVD (i.e. mpeg 2)? Assuming you're not getting a 35mm transfer, is there really any point in shooting it, even if to put on HDcam SR or something, since you would only be able to screen it at its highest resolution at a film festival with an HDcam deck, and an HD projector? Like, you couldn't just pop it into the family HDcam deck or something...

Also, in DVD compression, how can you maintain the HD quality while presenting your film in a format that can be seen by as many people as possible? Because, I found when shooting, that HD requires an enormous amount of compression to fit onto a DVD, and the quality degradation makes me think I'm either not thinking about this the right way, or just shouldn't be shooting it unless I can afford a high quality transfer to film or something. Also, how do professional DVD's (generally) look extremely high quality, even though they must be incredibly compressed to fit all the information for a feature film onto the limited space of a DVD? I'm talking about, say, Road to Perdition, or the Conformist or something, where obviously it was shot at extremely high res, but has to be put onto a DVD so the masses can see it? Because even if a film is shot in 35 or 65mm, theoretically doesn't it still have to conform to a compression that would fit onto a DVD? I'm assuming that the difference is that the information in a 35mm print can simply respond much better to compression, and can handle more 'degradation' than a miniDV image (that is already highly compressed). Am I way off here?

Also, to apply this to shooting film. Is there any point in shooting 16mm if you output to miniDV, since you end up sacrificing an incredible amount of information that was in the negative?

Thanks so much in advance.
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#2 Scott Fritzshall

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Posted 20 August 2008 - 03:34 AM

The reason to shoot at a higher quality is that having more to start out with gives you higher quality in the end. There is a very noticible difference between material shot on 35mm, 16mm, and miniDV, even when all of them are being watched on a standard definition television. Assuming that everything else was equal, shooting on HD for an SD finish will give you a higher final image quality than shooting SD for SD. This is why primetime television shows have been shot on 35mm for years. They could just have shot on Betacam, but the much higher quality of film made such a diffence to the finished product that it drastically increased the apparent production values. The other benefit is that if you end up revisiting it later, with more modern and higher-quality distribution formats, you've got the quality to fill it. If you're re-releasing your movie or show on Blu-Ray but it was only shot on Beta to begin with, then you're stuck with standard definition, but if you had shot it on HD or film, you've got much more resolution that you can fill the screen with.

DVDs are a standard video format. They conform to either NTSC or PAL resolution, and have a certain range of MPEG-2 compression applied to them. Film gets transferred to video with a Telecine, which scans each frame with a CRT or CCD, and converts it into the desired format. For years, this was standard definition NTSC or PAL onto formats like Beta or DigiBeta or D1. Now we've got HD telecines that can read it at a higher resolution and put it onto HD tape formats like HDCam and HDCamSR. Again, film contains a massive amount of data to begin with, so in keeping with the principle I explained in the first paragraph, the end result to standard definition and with MPEG-2 compression looks better than the end result for something that originated on SD.

You cannot put anything other than NTSC or PAL video on a DVD and expect it to play on someone's TV. HD video requires HD-DVD or Blu-Ray. I'm confused by your statement about shooting HD to DVD; are you using a consumer camera that records directly to DVD? If so, you need to understand that this is a consumer format that is not intended for even remotely serious filmmaking; real HD production records to HD tapes like DVCProHD, HDCam, and HDCamSR, and now to data on solid state or hard drive recorders. HD distribution for theaters is typically done on tapes like HDCam.

Ultimately, your shooting format can be a complex decision, and it should be strongly influenced by your intended destination(s). If it's only ever going to seen on YouTube by your friends, then you don't really need to worry about what it looks like. If you want it to be shown in festivals and seen widely, then image quality can make a big difference, and investing in a high-quality capture format can make a lot of sense. Ultimately, it's a question of priority.

Hope that helps.
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#3 John Sprung

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Posted 20 August 2008 - 12:39 PM

shooting on HD for an SD finish will give you a higher final image quality than shooting SD for SD.

This is because of the Nyquist limit and optical low pass filtering. There's a diminishing returns thing that kicks in at twice the output resolution. For instance, if you shoot 4K and 2K side by side, they'll both produce equally excellent SD.



-- J.S.
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#4 Jason Outenreath

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Posted 21 August 2008 - 03:34 PM

Thanks so much, this does clear it up. No, I wasn't talking about shooting with a camera that records directly to DVD. I was just wondering what the point of spending a lot more money for HD was if the quality could not be feasibly and accessibly maintained. But this makes sense. Thanks!
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