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Old March 7th, 2010, 06:23 AM   #1
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HPX 171 best recording workflow

Hi all! I was wondering: what is the best recording setup whit the HPX 171 to fully utilize the cameras 4:2:2 codec? . I've briefly read something about the HPX sub-sampling to 960 x 720 when shooting in 720p and that it's better to shoot 1080p and then down-convert to 720p in post... Is this true?
I don't fully understand pixel shifting so excuse my ignorance in this matter.

Last edited by Sanjin Svajger; March 7th, 2010 at 07:24 AM.
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Old March 7th, 2010, 10:09 AM   #2
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All cameras recording on DVCPRO HD will sub-sample 720p to 720X960, 1080p or i is sub-sampled to 1080X1280, a 3/4 horizontal sub-sample using anamorphic(rectangular) pixels.

This has nothing to do with pixel shifting done with the HVX200/200A/HPX170/500. If you are talking about recording more samples to gain luminance and chrominance information, then, yes, shooting in 1080 could be beneficial. The cameras above have native 540X960 CCD's, they are shifted to produce a 1080X1920 sample, then downconverted to 720p if that is the wanted recording resolution, then the DVCPRO HD codec will sub-sample from there.

Most of my clients shoot in 720/24P or 30P Native modes in order to get 2.5 minutes per Gb of recording time vs. the 1 minute per Gb of recording time in 1080.

If you're doing green screen work, or whatever kind of live action, best thing to do is test the camera in both resolution modes and compare the work flow and quality of your final delivery.

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Old March 7th, 2010, 11:16 AM   #3
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So, let me see if I got this right. The HPX 171 shoots no mater what format selected in 1920 x 1080p and the down-converts to the selected format in camera (I actually knew this but forgot) which is lets say 1280 x 720p. Then in the process of recording the material to a firestore or a P2 card the DVCPRO HD codec (if selected) sub-samples the recorded image which is now at 1280 x 720p to 960 x 720p. Am I getting this right? But wouldn't this mean that the image would be cropped or squeezed?
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Old March 7th, 2010, 11:45 AM   #4
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It is squeezed. The DVCPRO HD codec has always been an abbreviated raster codec, 960x720 for 720 and 1440x1080 for 1080. This goes all of the way back to the original Varicam.

Dan
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Old March 7th, 2010, 05:38 PM   #5
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Okey... But what does all this mean in terms of actual quality loss?
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Old March 7th, 2010, 06:56 PM   #6
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Quote:
Originally Posted by Sanjin Svajger View Post
So, let me see if I got this right. The HPX 171 shoots no mater what format selected in 1920 x 1080p and ......
It's not really correct to say it "shoots" in 1920x1080. It processes the three 960x540 chip outputs in a 1920x1080 matrix, then resizes each frame to what is to be recorded. Together with the way the green chip is physically offset from the red and blue, processing in this way means it achieves a luminance resolution of about 1200x650, though chrominance resolution can't be better than the 960x540 of the chips.

The reason for the 1920x1080 matrix is really to make the processing easy on the maths, it won't achieve anything like that resolution.
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Old March 7th, 2010, 11:52 PM   #7
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Quality loss? What quality loss? Have you used the camera? My suggestion would be to wean yourself of all of these relatively meaningless numbers, measurements and specs and go shoot something with the 170 and or the EX1 and whatever other cameras you are considering. The proof is on the screen, specs are incredibly overrated. One of the unfortunate side effects of hanging around user boards too much is the tendency to "measurebate" and obsess over specs that really are close to meaningless for the majority of users. IMHO, specs are really not very important, how the picture looks to you when you light and shoot well with it is by far more important than full raster versus abbreviated raster. color space and other such meaningless trivia.

I have the 170, it looks amazing and I have made some great pictures with it, some exhibited last year at the IMAX Theater in Copenhagen on a 65' screen through a 4k data projector. Nobody in the audience knew that the footage was shot on an abbreviated raster camera, the images looks great. I have shot lots of broadcast stuff with the EX1, it too can look amazing. When you are talking cameras in this level, all are capable of very high quality pictures if you are up to the task of composing, lighting and pointing the camera at them.

Good luck,

Dan
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Old March 8th, 2010, 01:52 AM   #8
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Yes Dan, I have the camera at home, for the third week now. I've tested it in many ways - even shoot a music video with it. I can't say that 100% happy with the material (don't like the soft-ish look). I do understand the point your making about getting obsessed with specs and stuff on the boards - but still, I do want to buy the best camera that's gonna suit my needs. And that's the reason I'm asking this.
I'm also interested in this matter no matter if I would be buying a camera or not...
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Old March 8th, 2010, 06:39 AM   #9
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Then, can you please define your requirements first? We know nothing about that aspect.
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Old March 8th, 2010, 09:02 AM   #10
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No requirements. No nothing! If I wanted to open a topic about me buying a camera I would have done so and there I would have stated my "requirements" (I've actually done this in the general HD forum). Here, I'm just inquiring about this specific question. And that's all.

--- I'm buying a camera EX or HPX. This inquiry is related to me doing this. Currently I'm in the process of figuring out if the HPX is going to meet with the HD standards (comming in a year) here in our little land (Slovenia). I know what the standards are, so no need for me to bother you with that. I just need to figure out how this camera works and then I'll be the judge. --> This topic doesn't belong here, but now you know. ---
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Old March 8th, 2010, 09:06 AM   #11
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I see. The best way for you to judge will be to actually use the camera to produce footage that you can judge yourself. I have a HPX172 here - PAL version. Excellent stuff.

All these codecs and numbers mean nothing - you just have to see the quality of the footage to compare. AND more important, the camera handling as well. It is useless to make a superior camera if it does NOT handle well.
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Old March 8th, 2010, 09:55 AM   #12
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Hi Sanjin:

Your comment that the HPX171 footage looks "soft-ish" means you will probably favor the EX1 IMHO. I have never heard that description applied to EX1 footage. On the contrary, the footage from the Sonys is razor sharp, even too sharp for my taste, but a lot of people in this business like that hyper clean sharp look.

FWIW, your perception of sharpness on the 171 probably has nothing to do with the abbreviated raster specs of the DVCPRO HD codec. It probably has everything to do with the fact that the HPX171 uses pixel shifting from lower resolution imagers and features a fixed lens. If you look at footage from the HPX2700, 3700 or even the original Varicam, it would probably not strike you as soft-ish.

The DVCPRO HD codec looks great as a camera codec, it is not so great as an editing codec though. I think what you are seeing is simply that the imaging system on the 171 is not what you are looking for.

Dan
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Old March 8th, 2010, 10:05 AM   #13
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Yes, EX1 or HPX300 would be sharper than a 170, plus a superior codec for the 300 vs. EX1, due to AVC-Intra 100. It has better ergonomics than palmcorders, albeit larger. The EX1 has 1/2" CMOS sensors, so very good in low light, DOF a bit shallower, but codec is low bit rate, Long GOP, 4:2:0. AVC-Intra is the only camera under $35K that offers internal 10-bit recording.

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Old March 8th, 2010, 10:57 AM   #14
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Yes, that soft-ish look is from the low res chips - but I just heard about the sub-sampling and wondered what's it all about :)

The HPX300 - I don't know, I've never used it - but I don't like the fact it has fulres 1/3 chips - but also haven't seen any footage from it, so I'm not to judge. If I would buy an EX3 cam, I would definitely buy the NanoFlash with it. And that would add up to approximately the same amount as the HPX300 goes for. Hence I don't care about the form factor (short films, commercials, music videos) I would definitely go for the EX3.
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Old March 8th, 2010, 11:26 AM   #15
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Yes, nanoFlash with EX1 is a good combo, however, it's still 8-bit, external recording, non-write protectable media. The EX1 is very good in low light, around ASA 640, depending on resolution(720/24PN is fastest)/frame rate/shutter vs. ASA of 320 for the 300, but I think you should at least check out the 300. No 8-bit codec can handle the amount of color correction and grading that a 10-bit codec can. I prefer Panasonic fleshtones over those of the EX1, YMMV.

Also, AVC-Intra has lower noise than DVCPRO HD and this helps get more latitude from the camera. DVCPRO HD looks very good with an HDX900 or HPX2700, even though it's sub-sampled, but AVC-Intra 100 is a big step forward, offering full sample Native progressive recording and better tonality than 8-bit codecs.

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