Hello all.

The topic of HD acquisition is new to me, or rather it is only recently that I have really started to look into which HD camera would be suitable for me.

First of all, like most, I have been waiting for something from Canon in the area of HD. Seeing that they were late in the market, one would think that something like the Pansonic Hvx 200 would have been released.

This brings me to the purpose of this thread.
In all the hype surrounding the affordability of HD under 10k, it appears that even with the Canon release that the Hvx 200 is the only true HD camera.

The rest appear to be "Glorfied SD."
When material records at 25mbps we truly have SD with an HD look and feel. Hence the term HDV I suppose.

As I have read through all the threads, newsbits, etc., the fact that true HD appears to be lacking, and that everyone seems to think they are getting an HD camera from the likes of Canon for 10k is a bit disconcerting.

I will admit freely that I am not a camera expert by any means, as stated at the beginning of my post.
So when I alluded to Canons apparent lack of true HD capabilities, know that I refer to the fact that it records, in camera, directly to 25mbps tape.

Now I have seen people record DVCPRO 50mbps material to DVCPRO 25mbps tapes. And apparently its true 50mbps on the 25mbps tape, with the only difference that it eats up twice as much tape when recorded on the 25mbps.

In saying that, perhaps you could have a canon record to DV 25 tape with 50mbps (still not hd is it? dont you need minimum 100?)

The other thing is pulling a good key.
It has been stated you need minimum 50mbps to pull a good chroma key.

So if we have a 10k canon that records to 25mbps tape (though it has the "look" of HD/film) then what good is it for serious stuff when its time to key?

(Now I dont understand what benefits the SDI might have in the studio for this camera in terms of quality. It appears you can get 50mbps, but I am trying to stick with the scenerio of what it records in the camera when in the field.)

All this to say, that the closest thing to true HD that i have found was the Panasonic Hxv200. I wasnt really looking at panasonic, but discovered it throught this board, ironically, while awaiting info on Canons H1.

The fact that the Hxv200 records to a P2 card is cool. (yes expensive, etc., but this is something all these guys should have gotten into...collaberated on to get the cost down.)

But seeing that Canon is part of the HDV consortium with Sony, its no wonder they didnt try true HD like Panasonic who is not part of their group.

Well, any clarification on the issues mentioned about the 25mbps rate would be appreciated. I know a lot of you are still trying to understand what all this means yourselves, especially since no one has really had a chance to even look at one.

Gods Peace

dAlen

The MiniDV tape would not be able to stand up to the increased speed needed for 50mbps recording.

HDV to me is a desperation format. The price of technology isn't really avaialble to give consumers/prosumers high def as yet, so something was built on the back of an existing format.

Tapeless formats are the way things are going, but there again the prices are still not there for the average Joe. These are all reasons why I will not jump through hoops to get buy a HD camera (aside from the fact that other than my own indie projects I haven't got any clients for HD).

...(Now I dont understand what benefits the SDI might have in the studio for this camera in terms of quality. It appears you can get 50mbps...)

Well how about uncompressed 4:2:2 to HD-SDI at 1.485 Gbps as opposed to HDV at 4:2:0 and 25mbps using 15 frame GOP via MPEG2 compression. I believe you'll notice a difference in quality there.

HDV as glorified SD. The Sony shoots a 1440X960 image. You can put 4 SD pictures in the space of 1 HDV. Makes a difference for sure. That was demo'd at our Apple FCP meeting.

But by all means, buy the Panasonic if you feel that's the right camera for you. Just make an informed choice and try to get hands on with any camera you are considering. The Panasonic is going to put out some beautiful stuff, but it's a fixed lens non-shoulder mount camera. IOW, you hold it out in front of you like the Sony PD-170 or DVX100A. That can lead to operator fatique in fairly short order.

-gb-

SDi is an okay option. But look at the kind of storage you would require! You'd be hauling a truck behind you everywhere you went! The camera is still only 1/3" too, which limits it quite severely.

No. The real HD revolution will come about once solid state media comes down in price.

Personally I think, like Ikegami, manufacturers should start using the AVID HD codec for storage on a tapeless format. Far more sensible.

SDi is an okay option. But look at the kind of

Personally I think, like Ikegami, manufacturers should start using the AVID HD codec for storage on a tapeless format. Far more sensible.

Yeah - let's give Avid another monoply to rip us off with

SDi is an okay option. But look at the kind of storage you would require! You'd be hauling a truck behind you everywhere you went!

Yes, this is where I was trying to go with my post.
It would be nice to see more flexible & affordable HD cameras for sale under 10k.

Can you explain to me what the issue specifically is with 1/3"?
How does this affect an HD shoot?

On a side note, how is HDV marketed to a client?
You cant really tout that its HD.

I indeed am trying to learn as much as I can about this before making any purchases. It is exciting to watch as this market unfolds, and I appreciate the responces I have receieved thus far.

Gods peace

dalen

In defence of HDV. HDV is deliverable 25 Mbps HD. It is higher bitrate than any HDTV broadcast you are likely to receive, and it has the resolution to qualify as HD. It certainly looks one hell of a lot better than DV, or pretty much any SD format I've seen tested (including DVCPRO-50), thanks to the ingenious compression at work. In my attempts to break the codec, I've concluded that I can't do worse than DV by shooting HDV - I can only do better.

Further to this, if the principles of compression used to make HDV what it is were applied to every acquisition system, by the time you got to the 100 Mbps of an i-frame only codec you could be recording 4:4:4 1920x1080 and seeing significant gains in image quality. HDV is a very smart solution to a problem of limited data rates. By the time you get up to HDCAM SR rates, you could be cruising at 4:4:4 4k resolutions.

As for the "solid state media" revolution - I'm not so sure. The problem with solid state memory isn't exactly price - it's capacity. Even though Moore's Law probably still applies... other technologies are already faster, have an order of magnitude more capacity, and are obeying the same laws. If we're getting into the business of uncompressed or at least neglibly compressed video we will need many TB of space - and I'm not sure solid-state will be up to that task.

Just imagine for example if Apple got on the bandwagon, and started pumping out RAID iPods. Take 4 60 GB iPods and put them in a super-speedy RAID array, and you've got yourself 240 GB of capacity (config depended obviously) on the go. The current price of 4 iPods is less than that of a 4 GB P2 card... (or is it 8 GB? Does it even matter?) You've got a factor of 30 difference.

-Steve

Well how about uncompressed 4:2:2 to HD-SDI at 1.485 Gbps as opposed to HDV at 4:2:0 and 25mbps using 15 frame GOP via MPEG2 compression. I believe you'll notice a difference in quality there.
-gb-

From what I am gathering it sounds like Canon made a good quality studio camera. Which is probably going to reach their intended market initially.

Maybe later they will have a good field camera. (once solid state media comes down in price.)

Gods Peace

dalen

In defence of HDV. HDV is deliverable 25 Mbps HD. It is higher bitrate than any HDTV broadcast you are likely to receive, and it has the resolution to qualify as HD. It certainly looks one hell of a lot better than DV, or pretty much any SD format I've seen tested (including DVCPRO-50), thanks to the ingenious compression at work.
-Steve

I did not realize that there was 25Mbps HD. So when you record HDV on a regular 25mbps minidv tape you get a higher bitrate? Or do you have to buy a specific 25mbps HD mini dv tape? (never heard of the latter.)

According to your post, recording HDV onto minidv 25mbps tape is better than DVCPRO 50. (I dont remember the exact source, but I seem to recall someone saying that their issue with the new canon was that unlike DVCPRO 50 they could not get a clean key with the 25mbps...which I have known in theory to be true.)

Thanks

Gods Peace

dalen

I did not realize that there was 25Mbps HD. So when you record HDV on a regular 25mbps minidv tape you get a higher bitrate? Or do you have to buy a specific 25mbps HD mini dv tape? (never heard of the latter.)

According to your post, recording HDV onto minidv 25mbps tape is better than DVCPRO 50. (I dont remember the exact source, but I seem to recall someone saying that their issue with the new canon was that unlike DVCPRO 50 they could not get a clean key with the 25mbps...which I have known in theory to be true.)

Thanks

Gods Peace

dalen


Dalen, DV and HDV both record at the same data rate (25Mbps) onto standard MiniDV tape. HDV tape has been released that is claimed to be higher quality. This does not improve picture quality, it only reduces the likelyhood of dropout and digital breakup on the recording.

DVCPRO50 is good for keying because it records in 4:2:2 colour rather than HDV's 4:2:0. This means the colour is recorded at half the luma resolution on DVCPRO50 and only 1/4 on HDV. You need good colour resolution to be able to pull an accurate colour key, for obvious reasons.

HDV may outperform DVCPRO50 when viewed in HD, but it is very unlikely to do so if you are downconverting it to SD.

It isn't all about datarates, the efficiency of the codec is very important too. HDV is a pretty efficient codec, being able to record a "reasonable" HD (1440x1080) picture into just 25Mbps. There are newer codecs that are even better, like H.264, but are not being used in cameras quite yet. There are some cameras being released soon that use MPEG4 compression.

DVCPRO50 is good for keying because it records in 4:2:2 colour rather than HDV's 4:2:0. This means the colour is recorded at half the luma resolution on DVCPRO50 and only 1/4 on HDV.

All true. The only thing that needs to be clarified is that DVCPRO50 records SD 720x480 4:2:2, and HDV records HD 1440x1080 4:2:0. There is more than enough information in an HDV stream to render out 720x480 4:4:4.

However, because HDV doesn't actually have 50 Mbps of real data, it is likely not going to perform as well on a mathematically intensive application such as keying. In SD resolutions though, it may very well be perceptually comparible or superior to DVCPRO50.

HDV may outperform DVCPRO50 when viewed in HD, but it is very unlikely to do so if you are downconverting it to SD.

I disagree. At SD resolutions they should be very comparible. At HD resolutions, the softness of upsampled DVCPRO50 ought to be equally offensive as compression artefacts in the HDV signal. The efficiency of the MPEG-2 GOP structure is rated somewhere between 2x and 4.5x, which places the effective data rate of HDV well near the 50 Mbps (or higher) of DVCPRO-50. The same can be said for a comparison between DVCPRO-HD 720p and the HDV1 720p standard.

I highlighted "perceptually" a little earlier - which is an important point to make. The objective of a compression algorithm is to lower the data rate without affecting the perception of the image quality. It is most definitely a fine art.

-Steve

Yeah - let's give Avid another monoply to rip us off with

Why a monopoly? The Ikegami cameras can already record to the Avid codec. On top of this you can download the Avid codec reader for free meaning that you can get any NLE software from Premiere to Vegas to read the files. On top of which it is a damn good codec that allows editing of full resolution HD files without needing a computer the size of a warehouse to process it.

Dalen, if you do, I just wanted to point out that all of the HD that you watch over cable or from a sattelite provider is usually 12Mbps or lower, and never higher than 18Mbps. So you are saying that this is SD?

HD has nothing to do with bit rate, that is a codec thing, it is only about resolution. Anything that is 1280x720 or larger is HD even if the data rate is 1Kbps. Of course I wouldn't want to key 1Kbps HD and not even 1080i HDV.

Can you explain to me what the issue specifically is with 1/3"?
How does this affect an HD shoot?
[QUOTE]

The issue, as I have mentioned many times before is that a 1/3" camera at HD resolutions cannot give anywhere near HD detail above around f5. Apparently the Sony Z1 etc have an option to stop you going above this f-stop for this very reason. Here is the technical explanation why http://forums.dvdoctor.net/showthread.php?t=35244&page=1&pp=10

[QUOTE]On a side note, how is HDV marketed to a client?
You cant really tout that its HD.

I'm not sure where this idea comes from? HDV is 1440x1080. That is high def by anyones standards. If you shoot HDV you *are* shooting high def. Its just that you are not shooting very high end high def. I feel that HDV was developed as a rush to market as a way for the manufacturers to help justify making us purchase new televisions capable of high resolutions. The technology isn't really here yet for efficient HD production at the lower level. But the electronics manufacturers want to sell more new televisions and they need a new selling point.

HDV is a limiting factor. Any camera worth its salt should record and compress individual frames. If P2 comes down in price soon enough and Panasonic introduce much lower end HD cameras that use it, I cannot foresee HDV lasting much longer. I can't see anyone choosing 25Mbps HDV over 100Mbps DVCproHD.

I believe HDV is an interim format. The development of solid state and optical recording is such that there will be a lot more flexibility.

This brings to mind the question "How good is the implementation of MPEG 2 on this camera?" As we all know codecs range from pretty decent to abysmal. In software we have the option of changing encoding parameters or of buying another software package. With a camera the algorithm is cast in concrete (well, silicon actually) so a good implementation is most important for anyone planning to use the camera untethered to a device which can take the SDI output. So, guys on the floor - please try to check this out for us!

<<<In defence of HDV. HDV is deliverable 25 Mbps HD.>>>

I have heard this argument before. Does this mean if you are delivering on
DVD you want to acquire footage at 6.4 mbps? Not me brother.

IMO, the HD I've seen via cable looks fine until someone turns his/her
head or smiles and then you see HORRIBLE macroblocks. Talk about
jaggies, the Olympic's looked hideous as soon as the action started.
I want to see beautiful people's perfect teeth and eyes, not a mosaic.

I plan to acquire my footage at the highest possible
quality I can afford and THEN deliver/compress it in whatever low resolution
format is required. I don't want to start with the lowest bandwidth at
the beginning of the production process.

Just spotted this:
[QUOTE]

The issue, as I have mentioned many times before is that a 1/3" camera at HD resolutions cannot give anywhere near HD detail above around f5. Apparently the Sony Z1 etc have an option to stop you going above this f-stop for this very reason. Here is the technical explanation why http://forums.dvdoctor.net/showthread.php?t=35244&page=1&pp=10


The reasoning here and at the referenced URL is backwards. The spread of the Airy disk (a perfect point source is spread on the image plane by diffraction so that it isn't a point but a disk with rings - the spread pattern is called an Airy disk after the first Astronomer Royal) increases as the aperture decreases. Thus if a lens is diffraction limited at f/5 you cannot use it a apertures smaller than f/5. At larger apertures it would be OK. It is true that a smaller CCDs require smaller apertures for a given image size and exposure so that the diffraction limit may be reached at high f stop numbers.

You can do a crude demonstration of this by taking two pieces of paper and forming a slit right in front of your eye while looking at a light background. The gap will appear to be filled with dark lines. The narrower the slit the farther apart these lines are. As you pull the pieces of paper apart these lines ((diffraction fringes) get closer together and collapse into the edges. The deal with a lens in the circular extension of this principal.

[Edit: unless of course by "above" f/5 they mean a larger numerical aperture and a smaller hole in which case the thinking is right though I guess I don't really think that a 5.4 mm lens is difraction limited at f/5 wrt a 1/3 inch CCD. No point in asking Canon for MTF data on this lens, I suppose but as people are there....]

Saying HDV isn't HD is like saying a DVD isn't SD or that DV isn't real SD because it is only 720x480 instead of 720x486.

What makes HDV not real HD for some people?

Is it the 1440x1080 resolution compared to the full 1920x1080 spec? Well HDCAM also uses 1440x1080 with 3:1:1 color.

DVCPROHD only uses 960x720 or 1280x1080.

So in terms of resolution 1080 HDV is just as good and 720 is actually better.

While keying may not be perfect with HDV it is a lot better than it was with DV. In the past however with DV we never had an option for uncompressed output. With HDV we now have options. If you really don't want to capture via SDI or component for HD then why not use SD uncompressed? It would be much better than DV and even DVCPRO50. You can even capture through an SDI card for $300.00 on the Apple as DVCPRO50 turning the XLH1 into a DVCPRO50 camera.

HDV is a limiting factor. Any camera worth its salt should record and compress individual frames. If P2 comes down in price soon enough and Panasonic introduce much lower end HD cameras that use it, I cannot foresee HDV lasting much longer. I can't see anyone choosing 25Mbps HDV over 100Mbps DVCproHD.

I believe HDV is an interim format. The development of solid state and optical recording is such that there will be a lot more flexibility.

I agree, HDV is not perfect for pro users, but P2 and DVCPROHD is FAR from perfect in lower end cameras. P2 is not going to be selling to consumers any time soon, as you are not going to be able to fit more than an hour of 1080i/p on P2 until 2007! Even then, you'll need 2 32GB cards which will be around $3000, WAY out of consumer territiry JUST FOR THE CARDS! Competition may bring prices down slightly, but don't bank on it.

Pany have started to introduce low end SD cameras which take SD memory cards, but may move on to record HD on SD cards - that'll really confuse consumers!

HDV is interim in the way that it records HD onto miniDV tape because no manufacturer was willing to develop a new tape mechanism when tape is nearing the end of its life cycle. Whether HDV's MPEG2 codec continues to be used on solid state remains to be seen, but it is then not technically HDV so for sure, HDV will die, but first it is going to completely dominate the low end HD world like DV has done since the mid 90's with SD.

I will quite happily bet that in 5 years there will be far more cameras shooting HDV than DVCPROHD, probably by a factor of 10.

I also believe that HDV will outlive DVCPROHD, which is already showing its age.

I am waiting for MPEG 4 cameras, with codecs like H.264. Even at 25Mbps that would look great!

<<<I also believe that HDV will outlive DVCPROHD, which is already showing its age. >>>

How old is MPEG2 again?

<<<I am waiting for MPEG 4 cameras, with codecs like H.264. Even at 25Mbps that would look great!>>>

Or at least a LOT better than HDV!!!

<<<I also believe that HDV will outlive DVCPROHD, which is already showing its age. >>>

How old is MPEG2 again?


Bitrate wise though, DVCPRO is not that efficient anymore. MPEG2 use is certainly increasing rapidly, and will continue to do so for some while.

Personally I would like to use something newer, we have better codecs, why not use them - Maybe it is just a question of processing power..?

Just spotted this:
[Edit: unless of course by "above" f/5 they mean a larger numerical aperture and a smaller hole in which case the thinking is right though I guess I don't really think that a 5.4 mm lens is difraction limited at f/5 wrt a 1/3 inch CCD. No point in asking Canon for MTF data on this lens, I suppose but as people are there....]

Yes, we mean above f5 as in numerically.

Alan Roberts, the guy who wrote the reply to me at that site, made his living out of that kind of thing. Walter Graff has also been commenting on this problem, which was the reason why I asked Alan about it. AFAIK the Sony cameras even have an option on their menues to limit the f-stop settings for this very reason.

I am waiting for MPEG 4 cameras, with codecs like H.264. Even at 25Mbps that would look great!Me too. A general rule of thumb is that MPEG4 requires about half the data rate of MPEG2 to achieve the same image quality.

What makes HDV not real HD for some people?


This is what makes it not real for me:
[Quote from Jacques Mersereau in earlier post]

IMO, the HD I've seen via cable looks fine until someone turns his/her
head or smiles and then you see HORRIBLE macroblocks. Talk about
jaggies, the Olympic's looked hideous as soon as the action started.
I want to see beautiful people's perfect teeth and eyes, not a mosaic.

I plan to acquire my footage at the highest possible
quality I can afford and THEN deliver/compress it in whatever low resolution
format is required. I don't want to start with the lowest bandwidth at
the beginning of the production process.

[End Quote]

This pretty much sums up the issue I think

If you really don't want to capture via SDI or component for HD then why not use SD uncompressed? It would be much better than DV and even DVCPRO50. You can even capture through an SDI card for $300.00 on the Apple as DVCPRO50 turning the XLH1 into a DVCPRO50 camera.

This is not a bad option, but it is only useful in the studio.
Not really practical in the field.

So, how old is MPEG2?

All this is theory, fact is shoot HDV bump it to uncompressed 10 bit and I have found ZERO issues with artifacts, we use HDCam as well and in terms of picture quality(not theoretical picture quality), once you've bumped HDV up to 10 bit the quality of the HDV material comes surprisingly close to the expensive cameras.

HDV is a revelation, some of you may turn your noses up at it saying it's not REAL HD, but I'm earning money with it now and I am very, VERY happy with the quality. The Panny cam may be good, but P2 and even the firestore (worlds most expensive hardrive) stinks for our docco workflow.

<<<All this is theory, fact is shoot HDV bump it to uncompressed 10 bit and I have found ZERO issues with artifacts>>>


Interesting. I know HDV does a good job most times, but
what kind of shooting and/or content do you acquire? You claim you
have never had a single artifact recorded to tape because of
HDV's compression? Is that what you are claiming?

If so, has HDV *ever* made you alter your shooting 'style' in order to avoid
compression artifacts?

<<<All this is theory, fact is shoot HDV bump it to uncompressed 10 bit and I have found ZERO issues with artifacts>>>


Interesting. I know HDV does a good job most times, but
what kind of shooting and/or content do you acquire? You claim you
have never had a single artifact recorded to tape because of
HDV's compression? Is that what you are claiming?

If so, has HDV *ever* made you alter your shooting 'style' in order to avoid
compression artifacts?

Jacques, with regard to mis-quoting, you'll find it much less likely if you reply using the quote button on someone's post. You don't have to include the whole thing but more importantly, if someone then quotes your post, any earlier post you quoted in it won't get carried forward and cause the scenario you referenced earlier.

Just a friendly wrangler tip for ya...
-gb-

HDV is a lot different than HD mpeg2 broadcast. A lot of times the bitrates used for broadcast are much lower.

Take 720p broadcast for example. Here we have a mpeg2 signal lower than the bitrate for HDV but on top of that it is compressing 60p instead of 30p. That means that even if you had a broadcast at 19.7 Mbits/s that video quality gets cut in half because of the double frame rate.

I know the Olympics were 1080i. Does anybody know what the bitrate was for that? I am sure it was lower than 25Mbits/s.

When 1080i is broadcast is it at 1440x1080 or 1920x1080? If it is 1920 then that means a 25Mbit broadcast would have slight lower quality than a HDV would due to the extra pixels. I think usually 1080i is around 12 or 15 mbits but I don't know for sure. It depends on the station.

For the most part the only people I have ever seen complain about the quality of HDV are those that haven't used it yet.

There was some footage recently on here shot with an HC1 at 1080i bouncing up and down some stairs with the camera shaking all over the place. The video actually held up very well with all of the messy motion going on. This was a heck of a lot more motion than you would usually see in a shot which shows that HDV can work very well.

A 1080i/p HDV video is about equal to a DVD encoded at 5.5 Mbits/s
A 720p 30p HDV video is about equal to a DVD encoded at 7.3 Mbits/s

A 1080i broadcast at only 15Mbits/s is about equal to DVD at only 3.3 Mbit/s

For example, our last shot was at an air display, so a combination of world war 2 aircraft, helicopters and fast jets, we filmed them taking off at speeds of about 100mph and then flying past at up to 400.mph. Takeoffs should be particularly tricky for compression, because when shooting from a tower there is a lot of ground reference including grass in the foreground. But even when panning at speed we found NO artifacts at all, certainly there was a very slight softening of the image, but this occurs with HDCam in a fast pan too.

We don't pay any attention to the theoretical limitations of HDV when we shoot and so far, it hasn't caused any problems.

<<<In defence of HDV. HDV is deliverable 25 Mbps HD.>>>

I have heard this argument before. Does this mean if you are delivering on
DVD you want to acquire footage at 6.4 mbps? Not me brother.

IMO, the HD I've seen via cable looks fine until someone turns his/her
head or smiles and then you see HORRIBLE macroblocks. Talk about
jaggies, the Olympic's looked hideous as soon as the action started.
I want to see beautiful people's perfect teeth and eyes, not a mosaic.

I plan to acquire my footage at the highest possible
quality I can afford and THEN deliver/compress it in whatever low resolution
format is required. I don't want to start with the lowest bandwidth at
the beginning of the production process.

HDV doesn't have that kind of problem. I am no big HDV fan, I dislike the format in fact, but lets give credit where credit is due.

You see the kind of artifacting you are talking about even for material acquired on 35mm. It isn't even an issue with the encoding to HD 12Mbps.

Its a failure of digital transmission.

Analog transmission has its own problems, but when it failed it did so much more gracefully.

The best channels (image wise) on my local cable are the popular ones which are still being sent down the wire as analog.

HDV's real failure is not as a format for acquiring moving pictures for display, but rather when those pictures must be manipulated. Try a difference key with a "clean plate." I don't know whether to laugh or cry when I think of that.

So, how old is MPEG2?

I think the format was agreed upon in 1994... I think. That might be when the DVD Video standard was agreed, I can't remember.

MPEG was 1992 and then MPEG 4 was end of the 90's, I think one version in '98 and one in '99.

Please feel free to correct me!

I agree that if you stuff 5 mm focal length and f/5 into the Rayleigh limit formula you would get a resolution of .004 mm for red (700 nm) light which means that a 1/3 inch chip could resolve about 1100 points along its long dimension. The XL2 would be right at the diffraction limit by that reckoning and thus if this was the correct model the new 20X couldn't be any better. This model assumes a simple 5 mm focal length lens with a 1 mm diameter stop in front of it. That is not what we have with these zoom lenses. A modern zoom lens has a section where the light is nearly collimated and this is where the stop is usually put. This stop does not have to close down to 1 mm to give an entrance pupil of 1 mm. To get a better feel for what I am describing take a modern zoom lens, put it in manual mode (off the camera) and look in the back end. Stop the iris down to the point where you can see the blades. Now rotate the zoom ring. The diameter of the iris will not appear to change (or if it does it will only be slightly and that will be due to the lenses - you won't see the blades move). This is done to convince you that the iris isn't coupled to the zoom ring. Now look into the front end. You will see an image of the blades. Rotate the zoom ring. The image of the iris (entrance pupil) will change dramatically in diameter with the zoom setting. Although the mechanical stop isn't changing the entrance pupil is. This lets the effective aperture of the lens remain constant as you change its effective focal length. It also lets you have a physical stop large enough that the Rayleigh limit is not reached.

The point is that though the effective focal length of the lens may be set to 5 mm and the entrace pupil may be 1 mm the physical stop is never that small. Light rays never get stuffed through an aperture small enough that they interfere with each other (in reality they do, of course, but in a good design this will reduce sharpness less than the myriad other ills which plague the lens designer).

As I said before, I doubt the new lens is diffraction limited - at least not at an aperture as large as f/5.

The new XL 20x HD lens goes to f/9.5 before closing completely. The previous 20x L IS lens for the XL2 goes to f/16 before closing.

Ouch! Another stop and a half gone. Even if I don't agree with these gents exact numbers I am beginning to see their point! Guess we'll have to get used to the idea of controlling exposure more with ND filters and less with the iris.

I guess I would consider the image softening on a pan (or otherwise)
to be a clever way to mask HDV bandwidth choking. Given the choice,
I prefer to be the guy adding blur to a clip as opposed to having
it occur whether I want it or not.

I guess what bothers me is that the promise of HD was *more resolution.*
This whole 'jumbo' compression thing is very much like "lawyer-ese". The
real truth doesn't matter, it's what you can make people believe.
Ulitimately, it is what you can get away with is all that really matters now.

Yes, much of what HD we see is sent at even lower bandwidth than 20mbps.
but WHY oh WHY do am I now starting to pine for a good old fashioned,
interlaced, composite NTSC signal?

The digital HD broadcast revolution has been hijacked and I am bummed.

[QUOTE=Thomas Smet]HDV is a lot different than HD mpeg2 broadcast. A lot of times the bitrates used for broadcast are much lower.

Take 720p broadcast for example. Here we have a mpeg2 signal lower than the bitrate for HDV but on top of that it is compressing 60p instead of 30p. That means that even if you had a broadcast at 19.7 Mbits/s that video quality gets cut in half because of the double frame rate.]

I am not sure these apparent relationships between 30P and 60P , and also between 720 and 1080i hold linearly true. In fact I am certain they do not. Mpeg2 makes good use of the fact that as you increase resolution there is MORE similar data both in time and space, so the compression becomes more efficient. For this reason HD needs about ONLY twice the data rate for about 4 times more picture content.

So, for example increasing the frame rate from 30 to 60 will not have a very big effect on the data required for the SAME picture quality as the frames change LESS between images. You may only have a 2 to 5% reduction in picture quality for this major change in picture rate, with the SAME final data rate.

Mpeg2 is a remarkably good codec at reasonable data rates and most broadcast artifacting appears because of statistical multiplexing limiting a given channels bandwidth...this causes horrible artifacts because mpeg2 then becomes inefficient. On a tape system the problem is different: the data rate is CONSTANT so if the codec and input filtering is optimal HDV will give good results...and does. Most of the time they will be better than DV because the stream really is retaining more overall information...the temporal reduction becomes very beneficial in these situations.

Even on a CUT such coding can be very good at spreading the data changes over lots of frames. The 19meg of HDV is more than sufficient for most real world situations.

Some real world relationships that seem initially obvious to us, simply don't apply to coding algorithms, this is why CODING continues to improve, and decoding was always what was specified first.

I guess I would consider the image softening on a pan (or otherwise)
to be a clever way to mask HDV bandwidth choking. Given the choice,
I prefer to be the guy adding blur to a clip as opposed to having
it occur whether I want it or not.


Well, there are a lot of factors that go into whether or not HDV or any other codec creates blur.

First off, you may be seeing exagerrated motion blur that has nothing to do with the codec. I see a LOT of that in DV and HDV produced materials. I am ashamed to say I see it in my own work ocassionally. It is due to bad technique.

Secondly and often in combaination with above, you may be seeing vectorized quantization. That is definitely a feature not a bug. What happens is the codec determines the direction a pixel is moving and applies motion vectors to it. You may be familiar with this from some high end MPEG-2 DVD compressors. The net effect is that the codec can replace lots of data with a bit of nifty math. (And its one reason you oget so much better performance from Altivec rather than MMX/SSE equipped processors on MPEG-2 video. Yes SSE3 made great strides)

DVD didn't use vectorized quantization anywhere near as much as HDV. That's why DVD so famously breaks up into blocks on motion, and why we end up having to increase the bitrates.

HDV on the other hand depends on cheap fast processors to use vectorization instead.

So, you have your choice of evils: Big blocky stuff on motion or some directionally correct blur. I'll take the latter.

Now, I would much rather have intraframe compression at higher bitrates, but considering what this buys I'll take the tradeoff.

I guess what bothers me is that the promise of HD was *more resolution.*
This whole 'jumbo' compression thing is very much like "lawyer-ese". The
real truth doesn't matter, it's what you can make people believe.
Ulitimately, it is what you can get away with is all that really matters now.


Well, that depends a bit on what flavor of HDV you are using.

1080i and 1080F/p flavors really show higher resolution.

720p flavors have it, but it can sometimes be hard to see. Of course having to use less bandwidth for the image data means less agressive application of the HDV codec, so with the same data rate you should get fewer compression artifacts.

IIRC there was a proposed 480p version of HDV which would have amounted to a inraframe DV. Prettier to look at, but with all the editing disadvantages of HDV. I think that was discarded early on in the codec standards process. It would have made an interesting comparison though between DV25, DV50 and HDV 480p.


Yes, much of what HD we see is sent at even lower bandwidth than 20mbps.
but WHY oh WHY do am I now starting to pine for a good old fashioned,
interlaced, composite NTSC signal?

The digital HD broadcast revolution has been hijacked and I am bummed.

Well HDV is what it is. I think of it as more related to DVD than what we are used to in an edit format. It is a great software engineering feat. We could do a lot worse than adopting it as the standard for next generation HD media to replace DVD.

Of course, MPEG4 has great advantages over MPEG2, and some newer codecs like H.264 deliver great results at lower data rates, but at the cost of more processing than you can expect to get into cameras and decks for a while. I am not sure if any PC solution can encode MPEG4 H.264 in realtime for HD resolutions, and I am likewise unsure how long it will be before we can.

Has the digital resolution been highjacked ? I don't think so. We are just very early on the road. Manufacturers didn't need to give us anything as capable as HDV, especially when it is so clearly an interim solution with a short shelf life.

I espect we will get a DV100 codec, like DVCPRO HD into these systems. DTE systems, like hard drives, will make this possible, but expensive. We will need a VERY high capacity media to archive footage. A 50GB BD-ROM (Blue Ray) will hold about 68 minutes of 100Mbps signal.

Anyways, I thin kwe agree on the symptoms of HDV and current HD production, but not about the overall market direction.

I think we are on the right road for now.