EX1 > SD better than shooting SD?

[Rainer Mann]

Hi
I have to shoot an interview for a media company (they will cut the stuff) They want to have 4:3/SD. I told them I wanted to use the EX which I will get this or next week. But they called it a "prosumer cam" - it would be better to shoot with a "big" SD cam. Well, as far as I know, EX is not "prosumer" at all and converting HD to SD should get a quality as fine as shooting directly on SD.
I wanted to shoot on EX with 4:3 grid in the viewfinder, opening a SD timeline in Final Cut Pro, taking the EX stuff to that timeline and exporting to an external Rekorder.
But this morning I read a thread about the bad quality resulting by that way... "steps" in lines etc--- recommendations? I will own an EX1 and still would have to rent an SD cam to get the best broadcast quality in SD 4:3 ? Hm... if so, ok - no problem. But I am really wondering...

[Paul Kellett]

I don't use Final Cut Pro,but i do use Vegas Pro 8 to work with my EX1 footage and there's nothing wrong with the footage once it's output to standard definition,on a DVD.The best way to get SD is to record HD then downconvert to SD.Hopefully some Final Cut users will reply for you but i can't see it being crap quality using Final Cut as a pose to Vegas.
Paul.

[Rainer Mann]

Thank you Paul. Hope to get replies about the quality of downconverting with Final Cut Pro and the best way to do so... I just don't "want" to believe having to rent an SD cam - but at least I want to deliver the best result to my customer !

[Andrew Wilson]

I think the footage looks really good once downconverted to SD but do some tests first. I find I get the slight stutter on a SD CRT television set since I shot in progressive and it's converted inside FCP to an interlaced format.

I haven't tried shooting in interlaced on the EX1.

Honestly, I think the EX1 really straddles the line between prosumer and professional leaning toward the pro side. It's still a sub-$10,000 camera and (I think) the best one available for the money today by far. It clearly delivers professional results from a prosumer looking package.

There's that old school expectation of a really big camera with Anton Bauer bricks stuck to the back and tape that records in 422 HD is what they need.

If you're brave, you could explain to your client that the EX1 shoots in 'industry accepted' XDCAM at full resolution and that since so few of your customers are still asking for SD, they're going to have to incur the expense of renting older equipment that they feel is superior. Plus, if they're cutting it, you should offer to get equipment that they natively support. I had a similar experience with a national broadcaster here. For them it was HDCAM or nothing. So I lost the job - but I'm also not supporting a $40,000 camera.

[Jon Carlson]

I had to use my EX1 on a re-shoot for a project that was originally shot in SD. It looked so much better than the original footage that I had to beat it up pretty bad to get it to match... besides scaling it down, I had to desaturate it and drop my brightness and contrast pretty heavily to get it to match.

Granted, I was matching it to footage shot on a JVC DV5000... not the greatest camera out there, but clearly the EX1 yielded superior results for an SD project.

I did have some minor problems scaling (Premiere Pro user) with artifacts. I took the footage into After Effects to scale and it looked fabulous.

FCP may or may not give them those same problems.

The only way I would see a big SD camera preforming better is with its bigger chips. I still don't know if it will be able to match the images that the EX1 is producing. Anyone have side-by-side comparisons available?

[Rainer Mann]

The stuff which I have to shoot will be cut together with other SD stuff. I am sure the EX stuff will look great, but will it match? Well, that's the question...

[Alexander Ibrahim]

At the end of the day use what the client asks for. It doesn't matter if they are wrong or whatever- just that they pay their bills. So- if they want you to shoot Digibeta or DVCPRO 50, rent the camera, charge them for the rental adding in a bit of markup get paid and get on with life.

That said they are dead wrong. The EX1 intercuts wonderfully with full size HD cameras. I've already intercut it with an F900 and a Varicam.

It also intercuts wonderfully with SD cameras. I've cut with it with XL-2 footage, and Varicam shooting DVCPRO 50. As mentioned elsewhere the only problem is that the footage is too sharp. That's easier to handle in post than the opposite problem of the footage being too poor in quality.

Also, do remember that the camera puts out 4:2:0 video. If they are planning on giving the footage an extensive post treatment (doesn't sound like it) then a 4:2:2 SD camera will match better- which leads you back to Digibeta or DVCPRO 50.

I see no problem with the HD to SD workflow within Final Cut Pro. I've done that with plenty of material, including footage from an HVX200. It is wonderful.

That said with the EX1 I prefer to use the camera's downscaling at ingest if I am working in SD.

[Ali Husain]

lol. the ex1 gives you 960x540 4:4:4. you have to corrupt it with a decimation filter to get it to look like 4:2:2or god forbid 4:1:1. by downresing the 1080p image by half you also cut the noise by a significant amount--is it 6db? so you end up with the ultimate SD camera shooting widescreen 4:4:4, with the ability to shoot in poor light and still produce a low-noise image, probably comparable or better than a pd-170.

vegas does a beautiful job of downscaling video. however there was a thread somwehre here a few weeks ago that concluded you get *slightly* better downscaled image quality if you use after effects.

[Ali Husain]

Originally Posted by Alexander Ibrahim

Also, do remember that the camera puts out 4:2:0 video. If they are planning on giving the footage an extensive post treatment (doesn't sound like it) then a 4:2:2 SD camera will match better- which leads you back to Digibeta or DVCPRO 50.

the ex1 can be corrupted to be 4:2:2

it is a 4:4:4 sd camera. for that matter the $650 hv20 is one too (except you'll get richer color and better lowlight for your extra $7000). :)

[Alexander Ibrahim]

Originally Posted by Ali Husain

lol. the ex1 gives you 960x540 4:4:4. you have to corrupt it with a decimation filter to get it to look like 4:2:2or god forbid 4:1:1. by downresing the 1080p image by half you also cut the noise by a significant amount--is it 6db? so you end up with the ultimate SD camera shooting widescreen 4:4:4, with the ability to shoot in poor light and still produce a low-noise image, probably comparable or better than a pd-170.

Uh... That is all wrong. Very very wrong. You do the entire community a disservice by posting such egregiously wrong information.

Well except your core notion that the EX1 is a fine, if unwieldy, SD camera.

The EX1 is 1920x1080, and its 4:2:2 if you capture live over SDI, otherwise it records XDCAM to SxS which is 4:2:0

The Panasonic HVX200 is 960x540, but that is also only 4:2:2. It does output 4:2:2 DVCPRO HD onto P2 though.

You can certainly record 4:4:4 video using the EX1 as a source if you want, but the sensors are 4:2:2. There is no way to get 4:4:4 video off this camera.

In fact you have to spend quite a lot of money to get 4:4:4 sensors. I don't recall if RED 1 has 4:4:4, but your next choice for 4:4:4 video is the Sony F950, Arri D20 and Panavision Genesis

[Alexander Ibrahim]

Originally Posted by Ali Husain

the ex1 can be corrupted to be 4:2:2

it is a 4:4:4 sd camera. for that matter the $650 hv20 is one too (except you'll get richer color and better lowlight for your extra $7000). :)

I already said it, but your information is so wrong I feel the need to refute it again.

The EX1 can NOT capture 4:4:4 video. Neither can the Canon HV20 or any other camera anywhere close to this price range.

[David Heath]

Originally Posted by Alexander Ibrahim

Uh... That is all wrong. Very very wrong. You do the entire community a disservice by posting such egregiously wrong information.

The EX1 is 1920x1080, and its 4:2:2 if you capture live over SDI, otherwise it records XDCAM to SxS which is 4:2:0

I think you're overlooking part of Alis post, where he says it gives 4:4:4 *AT 960X540*. On the face of it, I'd agree with those figures - the EX will record to card 1920x1080 luminance samples, and 2x 960x540 chrominance samples per frame - 4:2:0. Downres to 1/4 of the luminance samples and you're left with 3 rasters of Y,U,V, each of 960x540 - 4:4:4 960x540, as Ali says.

Whether the practice works out as sweet as that would imply may be another matter for all sorts of reasons, and those simple maths take no account of interlace effects, for example, or alias effects being left over from the downconversion. But colour space numbers are not absolute measures of quality, rather chrominance/luminance ratios, and the above example shows why quoting them without reference to the luminance figure can be misleading.

As far as the original question posed, then if they are editing the material, one point in favour of using a dedicated 4:3 camera is the convienience - shoot, hand over tape or whatever, job done. Client goes away, no waiting for ingest, processing, output back out.

[Ali Husain]

actually didnt' say anything about the sensors or about capturing at 4:4:4. if you downsample 1080p 4:2:0 by 2, the resulting image is 960x540 4:4:4, not 4:2:0. if you cut out an 852x480 portion of that image you've got 4:4:4 SD. if you want to get 4:2:2 SD from that, you have to make it worse by destroying chroma resolution in one direction.

[Matt Davis]

Originally Posted by Rainer Mann

But this morning I read a thread about the bad quality resulting by that way... "steps" in lines etc--- recommendations? I will own an EX1 and still would have to rent an SD cam to get the best broadcast quality in SD 4:3 ? Hm... if so, ok - no problem. But I am really wondering...

I've just come from a job cutting a project shot on 2/3" (a DSR-450 with $18k lens) & DVCAM, with a Z1 as B-Roll. We also happened to have a loaner EX-1 which I played with whilst waiting for the shooting crews.

Firstly, with the current software from Sony, everything zips into Final Cut quickly and easily. Astonishingly fast compared to my P2 experiences last year. Once detail was turned off and colour saturation raised a little, nice rich images.

I was interested in 720 at 50p, which I though would provide the benefit of longer shooting times and perhaps more success in becoming 50i when downsampled, yet easier to scale initially because of being natively progressive.

Just throwing 720p50 onto a DV PAL timeline and rendering it out provided results that didn't quite match the DSR-450 (that's an example of English Understatement). It wasn't horrible, just disappointing in comparison.

The image was lovely, luminsecent, radiant, rich in tonality. It just lacked the sparkle and zing of the original 720p footage. The zing and sparkle was in the DVCAM footage from the DSR450, and I would have said the EX1 matched it at native 720p (and you could buy two EX1s and more for just the DSR's lens).

I think the problem was in the scaling method, and possibly that I should be working with 1080 down to SD, not 720. It will require a resize from 1280x720 to 960x760 (distorting the pixels from square to CCIR-shaped) then an edge crop to 720x576 to get 4:3 PAL.

I will try custom settings in Episode, Compressor, QT Pro and Sorenson Squeeze. Just one little variance in a setting with compression software can mean the difference between art and compost.

My other alternative was to shoot 25Mbps quasi HDV and use an M15 deck to downconvert it to DV a-la-Z1, but taking the quality of the glass, Exmor chip and progressive nature with it. But I didn't get round to testing that, and now the EX1 is back with its rightful owner.

[Alexander Ibrahim]

Originally Posted by Ali Husain

actually didnt' say anything about the sensors or about capturing at 4:4:4. if you downsample 1080p 4:2:0 by 2, the resulting image is 960x540 4:4:4, not 4:2:0. if you cut out an 852x480 portion of that image you've got 4:4:4 SD. if you want to get 4:2:2 SD from that, you have to make it worse by destroying chroma resolution in one direction.

Wrong. For different reasons than I originally thought, but still completely wrong.

You make one fatal assumption... that downsampling will throw out only those Y' (luma) samples for which there are no corresponding Cb and Cr samples.

Turns out you can't do that.

Y' is a calculated value, not a sampled one. The camera sensors sample R G and B. Then they gamma correct that to give R' G' and B'. These are given a weighted sum to lead us to Y'. There is no actual green data in a video signal in either rec 601 or rec 709.

So... if you did resample the image in the non-linear fashion you suggest you would seriously harm the Y' component. So, your reduced resolution image would not be 4:4:4 but rather 2:2:2.

Now, in other places on this forum I talk about the fact that the relative values of chroma subsampling matter a great deal for digital compositing.

However for visual perception the absolute value of the Y' sampling frequency is paramount to the sensation of "sharpness" in an image.

For some test images this method of chroma resampling you suggest would in fact work splendidly. The image wikipedia uses to demonstrate chroma subsampling is just about an ideal example.

http://upload.wikimedia.org/wikipedi...ing_ratios.png

Also, solid fields of colors difficult to represent in 4:2:0 or 4:2:2 would benefit.

Most images however are quite irregular, and would suffer from having green "samples" misaligned. In other words it would be as if you'd applied a slur to the resampled image.

This is why video systems don't resample and rescale an image for lower resolutions, but instead simply downscale them. Its better to preserve the correct alignment of the green samples and the resulting Y' value than to try and create color information from thin air.

Perhaps more esoterically, if we were to follow your method we'd have to account for the fact that Kb and Kr have different values for SD and HD imagery. This would introduce errors in the conversion that would alter luma even further. The point being that not only will you throw away your resolution, but when you convert to SD from HD you are likely to distort colors, thus obviating the reason we started all these gyrations.

I suppose it is important to point out that a camera such as the EX1, could in fact sample 4:4:4 960x540 video with modest adjustments to its sensors and A/D conversion circuitry. The image would be biaxially pixel shifted and probably very pleasing. The moderating point is that these adjustments would have to take place in the camera before the image was recomposed as Y'CbCr. (Probably before it was converted to R'G'B'.)