To some extent you are correct. It's the total system from camera to projection system that defines the CoC values. And indeed video cameras oftenly employ optical low pass filters to minimise aliasing problems, that's why in some cases putting HD lenses on a SD camera isn't such a wise idea. Also of course the lens itself may be a limiting factor.

However all that's changed between the PD170 and the Z1 is the overall resolution of the system, the sensor is the same size, 1/3" and yet nobody that's shot with a Z1 and a PD170 or VX2100 would argue that the Z1 doesn't have a shallower DOF when the image is viewed properly.

Is this shallower DOF of much use, for my money no, if you want a 35mm like DOF pretty much useless. But it's a trap and that's the important thing, focus can become critical shooting with a Z1 or any HDV camera.

Looking at it another way around, can you get a shallower DOF by changing lenses. Not in a practical sense. Even if you could put the best glass made onto a PD170 you're not going to get an improvement, the sensor limits resolution and hence DOF. IF you could build a 4K 1/3" sensor and put that inside a PD170 you'd get reduction in DOF, pity the rest of the image parameters would be blown to garbage, one day maybe however CA would become a huge issue and there's no fix for that.

That's the other big limitation with small sensors, get over around F8 and you have another problem to contend with. That's why putting really expensive glass onto cheap 1/3" HD cameras makes no real sense.

By the way, since you bring up CA.....
one thing Adam Wilt didn't bring up in his camera comparison is lens quality. I'm really happy with my JVC GY-HD110...BUT...the 16x5.5 stock lens has quite a bit of CA when zoomed in all the way. I've replaced the 16x with a fujinon 17x5 and the problem of CA is better but not eliminated. Interestingly, the CA is VERY significant when out of focus. So much so that I use the amount of CA is a OOF indicator. The 17x doesn't breath like the 16x, and is constructed of all metal, rather than plastic. I suspect at $18k, the fujinon 18x is quite a nice lens, optically. You get what you pay for.

In still photography, there is software to eliminate the CA (using lookup tables to store CA for common lenses), and other optical aberrations can also be corrected automatically.

Digital cinematography has always been behind digital still photography in these areas because of the massive amount of processing and data shuffling needed, but with today's hard drives and CPUs it should be more practical. Still, it may be that the software will have to be rewritten for 4:2:0 color sampling (for those who shoot HDV).

>>>It's the total system from camera to projection system that defines the CoC values<<<

Here we have to be careful to differentiate between desirable and achievable diameters of the Circle of Confusion. The first portion of the article tells how CoC is derived and the second discusses what is achievable. In other words, the standards for CoC are based on specified viewing conditions and this in turn generates your DOF tables for specific lens focal lengths and apertures. However if your system performance cannot meet that standard, then you have to accept reduced viewing standards (view from further away or view smaller images) for a point to appear to be sharp. DOF is a subjective judgement and the better the system the more easily you can judge errors in focus. A poor system doesn't have greater depth of field, it just isn't in focus anywhere under standard viewing conditions.

Here's the way I look at it:

If you are shooting a documentary that's going to be shown in a science center theater, there is absolutely no comparison, the XD-Cam will blow the HDV stuff away. If you look at the same project on a 50" HDTV, the difference even down to the consumer level HDV stuff is really subtle to the average viewer. That's why Sony and Canon are taking the audio inputs off their consumer grade cameras. They're forcing people to go at least prosumer grade because the quality even on the low end HDV stuff is spectacular.

Laurence,
I think I haven't understood your point here. Your statement appears to be contradictory and I'm confused about it in relation to the points farss has raised..

My post is more related to the article linked in the first post, where a number of HDV cameras where compared, but an XD-Cam was thrown into the comparison. My point is that if you look at the cameras in the article, the HD-Cam is on a whole different level, but most viewers will not be viewing it in such a way as to make this relevant, whereas, all the HDV cameras (even down to consumer grade ones not mentioned) really exist on a separate plane that is highly compatible with the current batch of HDTVs. As further posts point out, there are optical issues related to the size of the sensors and the precision of the glass that a a certain format can make use of, but in the end, my opinion it is all related to what a project is presented on.

My point is that if your final presentation is theatrical, the larger 2/3" sensors, thirty thousand dollar glass, and the 10 bit dynamic range and lower data compression of XD-Cam all makes sense. I have recently worked on two HD-Cam shoots covering the red tide algea blooms off the coast of Florida. These are destined for Florida science center theaters and HD-Cam is exactly the way these should be shot. If we were to shoot such a project HDV, it wouldn't be of the quality that people expect in such a setting and the quality difference would jump out at you in that setting.

Another issue is broadcast. The way it was explained to me is that when a show is broadcast on say Discovery HD, it gets compressed at a very high ratio for broadcast. By the time a viewer watches it, it looks quite similar to a project shot on HDV. However, if they were to compress a project that was already highly compressed such as HDV, the double compression would be quite noticable. The reason I'm bringing this up is because, even if you stuck $30,000 glass on an HDV camera and if that camera had the 2/3" chips you need to make use of this glass, you'd still have this issue.

For most of the projects I am involved with however, the best that anyone will ever see them is a 50 or 60 HDTV and they will be viewed at best on an HD-DVD or BluRay player. Currently I am playing back HDV stuff as raw m2t files on a Playstation 3 connected to an HDTV, and so I am already looking at the quality that will be the delivery format of choice for the next few years. That quality is just wonderful by the way. Anyway, if that is the best medium I have to worry about, all sorts of compromises are possible with minimal noticeable difference. The quality compromises of 1/3" chips, prosumer grade glass and the 8 bit HDV format are just not an issue for me at all unless the final playback is going to be either theatrical, or I am looking at needing to supply a quality master that will survive the damage of broadcast compression.

Sorry if I seemed (or still seem) to be self contradictory or rambling off course.

Bob (Farss) -

I hear what you are saying vis a vis PD170 vs Z1, totally agree with your observation, but don't agree at all with your conclusions.

And (before I jump into my thoughts), there is still ANOTHER issue that we have yet to discuss that is vital to all this.

Ordinarily I wouldn't even continue this thread (as a writer), but I'm SO engrossed with sharpness and delivery right now, that I'm becoming somewhat of an experiential expert, simply by virtue of experimentation and "hair pulling".

So the following are NOT "referenced authority" facts; rather they are my own personal observations.

1 - We are in the midst of a huge media ACQUISTION and DELIVERY revolution. As cinematographers (or really Videographers or more correctly Digiographers) it is our duty to learn to control the media with which we are working.

2 - The ACQUISITION has moved (for us) from film, to analog videotape, to SD Digital cameras to HDV (and HD) cameras.

3 - The other side of the picture that has also radically changed is DELIVERY. Never discussed but totally obvious (the big elephant in the room) - and that is; we have all moved from CRT interlaced projection (within the tube) to Plasma and LCD "line-free" imagery. No Scan Lines. Big difference - what was once acceptable now becomes ugly.

Your issues about the "DOF" of the Z1 vs the PD170 are not correct in this respect. It's not a more limited DOF that you are experiencing. It's a limitation of the len's resolving power being exposed. The HDV camera has a 4x greater resolving power than the SD camera. At the same time, we are VIEWING these images on a far better platform - the plasma/lcd panel - at a MUCH higher VIEWING resolution that what we have traditionally "shot" for. A 50" LCD panel (at 1440x1080) is a hell of a lot shaper than a 50" CRT at 720x480. In fact, a 50" CRT is just plain ugly.

So your camera better be sharper, too.

I believe that the limited "Depth of Field" that you are commenting on in the HDV vs the SD is not that at all. It is simply the revealing that what we used to shoot wasn't all that sharp in the first place - we simply couldn't see it. Now the emporer has no clothes.

The higher resolution of HDV coupled with the new viewing devices, all at a dramatically higher resolution demands a more critical focus. That is not depth of field. That IS circle of confusion. It's also a "bitch" to deal with.

So.... one last time. Depth of Field is the amount in front and behind your subject that is "soft". In a limited DOF situation (like a tight head shot with a long lens) virtually EVERYTHING in front or behind the head is soft. That is the "35mm film" look and it is a useful tool that I dearly miss. (Isolate the person in the frame, visually) In a wide DOF situation (same tight head shot but with wide angle lens), essentially EVERYTHING in the frame is in focus. Again a visual tool that we utitlze for dramatic and practical reasons. (Hey Everything's in focus - use it).

To get a greater amount of control of your DOF, you need a larger image surface - not more resolution.

Now - one other thing - utilizing this amazing new resolution, I SHOULD be able to do a 4x optical zoom-in from my HDV footage and get the exact same image as my SD.
In fact, I can't - because the lens isn't up to it. And there in lies the rub.

But, in fact, that's exactly how it has ALWAYS been. That's why when we had the bucks (budget) we'd always opt for Cooke lenses vs Angenieux. They were just BETTER. And you could see the difference - immediately. The difference in cost might be $12,000 vs $70,000. Still a long way from from whatever the manufacturers can supply in a $5,000 camera.

I agree with Wilt and with Laurence. If you're delivering to a DVD audience - the equipment that we've got today, is absolutely "up to the job". In many situations, you won't even be able to "tell" if the movie was acquired with a $5,000 or $50,000 camera. If you're hoping to project bigger - you're going to need better.

And (my thoughts), if you want that 35mm film look, and the beauty of limited (or more correctly more controllable DOF) - the P&S and Red Rock are the only real available solutions, today.

v

Another thing:

If you go into your local electronics superstore and come out with the biggest, best Plasma TV you can afford, the chances are pretty good that it will be a 720p model. Not that this is bad. The image is still spectacular. It's just that slight softening of the 720p downrezzing makes the difference between full HD and HDV even harder to see.

If you look at full HD cam on a broadcast monitor, it really is spectacular. One thing you notice is that there is no moire effect on sunsets: just a gradual blend from color to color. You look at HDV on the broadcast monitor and you'll see lines where the color makes the jump from one rounded off number to the next. Now if you look at the same sunset on an LCD HDTV, you'll see the moire pattern no matter what it was shot on. It just doesn't make any difference. HDV is just fine. Now take an HDV project into a science center and project it accross 60 feet and those moire patterns and compression blocks that were impossible to see on the best HDTV at Best Buy will just jump out at you.

For me personally, I just aim for a decent HDTV and don't worry about things beyond that. With that in mind, I'm just fine with HDV cameras, $300 widescreen adapters, 501c heads, $400 microphones, etc. It is kind of like the 10% rule that electrical engineers use when specifying components. As long as everything is within an acceptable range, the project as a whole will be within that same range.

When I watch my own projects in my living room in HD with the project playing a 1080i m2t render off a DVD-R in my Play Station 3, the quality looks just wonderful, and I am confident that it will look that good in living rooms everywhere (once the HD-DVD vs BluRay battle is played out that is).

Every so often I get hired on as an assistant camera guy on a full HD shoot and I still am in absolute awe of the format. Some day soon I hope to see this Red Tide project that I have been working on recently in a science center somewhere around Florida. When it happens, I'm going to invite all my friends. We'll go to the science center, watch the show and have a big party afterwards. Watching a project I worked on in that setting will be one of the artistic high points of my life. It will be way beyond anything that I and my HDV level equipment are capable of. I am very aware however, that if at some point if it is possible to go to the science center giftshop and buy a BluRay disc of the movie, when I take it home and watch it in that setting, that the difference between it and my own small scale HDV projects will be subtle at best.

>>>we simply couldn't see it. Now the emporer has no clothes.<<<

Vic, I agree and that's what I said above (but more boringly!).

Serena

Now if you look at the same sunset on an LCD HDTV, you'll see the moire pattern no matter what it was shot on. It just doesn't make any difference.

I think you've been looking at old 6-bit LCDs. Doesn't happen here.

Plasma screens are harder to make in higher resolutions, so yes, they're more likely to be 720p than LCDs that are relatively more easy to crank up to 1080p.

What's the difference between MPEG-2 compression blocks from HDV and MPEG-2 compression blocks from cable or satellite showing F950 "full HD" footage?

:O)

Victor,
I could go into lots of technically stuff about how CoC is what's used to define those DOF charts that you referenced before but I'll pass :)

So long as we all understand that for whatever reason we have to take a lot of care with focussing when shooting HDV if we plan on HD delivery on a big screen, I'm happy.

One thought that has entered my mind on this too that probably affects what you're saying about zooming in on HDV. I suspect the other issue is sharpness, these HDV cameras are doing some degree of electronic edge enhancement, I think a bit of the Wow factor with HDV is it looks sharp, on a big screen it can look sharper than 35mm. But if that's because of some degree of digital voodoo it would come unstuck when you try to zoom in on the image.

I've noticed this on some "HD" TVs, from a ways back they have a real "look at me" kind of image but when you get up close (zoom in!) the image really falls apart with ringing on the edges etc.

Bob.