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General HD (720 / 1080) Acquisition
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Old August 7th, 2005, 04:09 AM   #1
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Are prosumers cams unable to utilize HD detail?

Somone showed me pics of downconverted dvpro HD to SD from a big gun camera. The result was a stunning amount of detail even in SD. Now HDV shows almost as much detail in HD, but when it's downconverted it doesnt look much different, or different at all to SD DV. Now I dont want to get into the argument of how downconverted HDV looks, that belongs on the other thread. But it seems to me the combination of mpeg2, a consumer lens and 1/3 chips don't allow downconverted HDV to be good as it could be, in that it does not preserve as much detail as the 1080 picture should even in SD.

I mean in HDV the detail is certainly there, but in SD it does not show that much an advantage. I think its the camera's fault, you really need a big lens, a big chip and better compression than mpeg2 as used in HDV.

Last edited by John Poore; August 7th, 2005 at 06:51 AM.
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Old August 7th, 2005, 10:01 AM   #2
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Well, putting aside the issue of HD, take a look at the difference in a 2/3" SD camera vs our prosumer 1/3" cameras. It's very noticeable to me. But then you don't really expect a $4,000 camera to look as good as a pro camera where the lens alone costs three times that much, do you? :-)
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Old August 7th, 2005, 10:06 AM   #3
 
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Quote:
Originally Posted by John Poore
I mean in HDV the detail is certainly there, but in SD it does not show that much an advantage. I think its the camera's fault, you really need a big lens, a big chip and better compression than mpeg2 as used in HDV.
Sorry, John, but you get a huge argument from me on this one. I don't know if it's your display, if it's your downconvert process, or something else, but the difference is crystal clear even with heavily compressed formats like MPEG 2 on the final output. I'll figure a way to get a file up on our website for you to look at that is shot as hdv, displayed as SD, and further, I did a zoom on the SD downconvert, and there is still a substantial difference. I do this sort of work every day, and whether I'm finishing in SD, or finishing in HD (which is rare) the difference is very clear and uncontestable.
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Old August 7th, 2005, 01:50 PM   #4
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Douglas, I take it you've seen the fine pattern pic I posted on the other discussion with HDV and DV split screened. That's what I am seeing and it's not just me.

I'd be pleased to see a frame grab of this quality you're talking about, but as I've said, take a look at the evidence, that's what I am seeing. It's nothing do with the monitor either.

Here it is, top 50% = dv, bottom 50% HDV downconverted.

http://www.greenmist.com/hdv/poore/hdv-dv%20testing.jpg
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Old August 7th, 2005, 02:49 PM   #5
 
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Screen grabs don't tell much of the story, especially when you're grabbing as jpgs, further corrupting the image.

http://www.vasst.com/streaming/HDV_downconvert.mpg tells a much better story, and although this is all done at SD, you can see more than one reason that shooting HDV and downconverting is better than shooting DV at any angle.
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Old August 7th, 2005, 05:35 PM   #6
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Thats really convincing douglas.

I know we had this discussions month ago, but still I don't get that good downconversions in Postproduction.

My workflow is: Capture from Z1 with Premiere Pro 1.5 (with the free hdv) or (even better) CapDVHS. Then immediately convert to TGAs.

In Aftereffects I use the right field order, scale it down and output progressive to DV AVI. But the result still doesn't look as good as the Camera-Downconversion of the Z1 or like your HDV_downconvert.mpg

How was that mpg done ?

Thanks!

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Old August 8th, 2005, 12:29 AM   #7
 
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The 1080i half/segment was captured as 1080i in Vegas, edited at 1080i, and rendered to 720 in Vegas.
The 480 half, was captured from the camera with the camera doing the downconvert, and then edited from there, always being SD. Both processes were done in Vegas.

I've got some better examples, just running out of time before leaving for a tradeshow, and keep having upload problems. We're at near capacity on our server with all the HDV and related clips up there...
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Old August 9th, 2005, 10:41 AM   #8
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I am still kind of new to this downconverting, why downconvert, why not wait ...edit native(fcp or avid) in hdv and then do a good downconvert? What is the best way ? how can you also possible compare them as you need a HD tv to see the one and an sd tv to see the other?
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Old August 9th, 2005, 11:51 AM   #9
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I think it would be best to capture and edit in HDV even though it may be slower. Then when you are finished you have more options.

1. You can export the project as HDV back to tape for a HD master.
2. You can down convert in software and make a DV master.
3. You can down convert in software and make a SD DVD.
4. Down converting in software will give you better chroma resolution.

If you capture and edit as DV and then in the future if your client wants a HD version you will have to edit the project all over again or make plans for doing a new edit by making an EDL.


One point as to why software down conversion is better than in camera down conversion or shooting native DV is the color space. When you shoot DV or down convert to DV you end up with 4:1:1(NTSC) or 4:2:0(PAL) color space. No matter what the BBC says software conversion will always give you better chroma detail because you are not throwing away chroma detail. When you use software to down convert you can end up close to 4:4:4. It isn't perfect but it is a lot closer than DV color space.

I think the reason why the BBC doesn't see much of a change is because HDV and PAL use the same type of color space.

NTSC is actually pretty bad for DVD since mpeg2 uses 4:2:0. converting 4:1:1 to 4:2:0 can kind of leave you with a 4:1:0. Encoding SD DVD's with a 4:2:2 or better source will give you much better results. Even for PAL starting with 4:2:2 or better would give slightly better results. Even though both use 4:2:0 PAL and MPEG2 use a different line order for chroma samples so the chroma could get interpolated.

Down converting in camera can kill a lot of chroma detail as well as add regular DV compression artifacts. Using software conversion can give you a high quality uncompressed master.
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Old August 10th, 2005, 09:22 AM   #10
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thanks for the info...that makes a lot of things clear...
I have a few questions for you 1) how do you downconvert in the camera?
It does different formats but that can not be downconverting I think..Is there a setting to downconvert? I havnt found it...
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Old August 10th, 2005, 03:46 PM   #11
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Hey John,
I'm going to have to disagree with your original statement. Sounds like the samples of the down-converted dvcHDpro footage where done correctly, and that most of the HDV you've seen has not been done correctly. Here's a video I put together for 1gracing. They are the US importer for Noble.

http://www.1gracing.com/images/noble-m12.mov

Everything in that video was shot on an FX-1.
Now tell me, could that be done with a DVcam? Did the DVCproHD look better than that?

Any of the footage that was in slow motion already had it's resolution cut in half due to splitting the fields to get 60p frames. Yet even after that loss it still looks incredible!

So I guess my point is, it's not the camera's problem. It's the person using it that causes the difference.

My 2 c,
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Old August 10th, 2005, 04:51 PM   #12
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David,

When you shoot HDV, but then set up the menu to export DV, that's downconverting. Read up on the menu settings.
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Old August 11th, 2005, 03:09 AM   #13
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Hi, I havnt been able to download anybody's video here, simply because I don't have the bandwidth to do it right now, but I'd love to see frame grabs, if anyone has bothered to do a scientific comparison, in the manner I have made an example of. I find it tough to tell the difference with anything in .mov format anyway, and what is it relative to? I am saying we need to see HDV/DV side by side to make an accurate comparison. I am not saying people are not apparently getting better quality, and there may indeed be ways to do it, for example as Douglas strongly advocates, if you use a strict workflow of Sony only products, then blammo, it all comes together. After this we have the opinion of some fellow called Eric James who feels in his considered opinion I have no idea how to operate a camera and that is enough reason to dispel the argument.

I have posted an example of a direct DV/HDV comparison, the HDV being downconverted in-camera, judge for yourselves or offer something similar to disprove it, not simply your favourite clip, you can't tell anything from this on its own.
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Old August 11th, 2005, 04:27 AM   #14
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I am currently testing the jvc GY-100, its a great little camera, the professional features and so on...but the MPEG conversion of HD makes the quality of the picture not much better then my old Xl1...When viewed side by side...
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Old August 11th, 2005, 06:45 AM   #15
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John,
You don't have to take it personally. If your not willing to look, then how can you make comments like that?

Here is a screen-grab in SD from the same thing. I don't have a version that was shot in DV, but take a look and tell me if you think any DV cam could capture this image as well:

http://www.expertmagic.com/dvinfo/nobleframegrab.jpg

All I was saying is that the difference between the DVCpro footage you saw and most people's HDV is what they do with the image once it's captured. Most people using prosumer HDV camera are not going to do nearly as good of a job as people shooting on pro equipment. Not because of the equipment, but because of WHO uses it.

A good example of this is the movie "28 days later". Many people with the same camera could never get anywhere close to how good it looked for DV. What's the difference? The person using it!

My 2 c,
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