<<<-- Originally posted by Rob Lohman :
2. true 16:9 (whatever method)
- resolution and FoV increase in 16:9 compared to 4:3
- 4:3 is lower resolution than 16:9 (that is the whole idea)
-->>>

Rob, if DV is 720x576 (or 720x480), whether it is 4:3 or 16:9, why do you say there is an increase in resolution in 16:9 compared with 4:3? I would agree there is an increase in resolution if you compare native 16:9 to stretched 16:9, but not that one set of 720x576 samples is higher resolution than another. Am I missing something?

Richard Hunter

<<<-- Originally posted by Richard Hunter : <<<-- Originally posted by Rob Lohman :
2. true 16:9 (whatever method)
- resolution and FoV increase in 16:9 compared to 4:3
- 4:3 is lower resolution than 16:9 (that is the whole idea)
-->>>

Rob, if DV is 720x576 (or 720x480), whether it is 4:3 or 16:9, why do you say there is an increase in resolution in 16:9 compared with 4:3? I would agree there is an increase in resolution if you compare native 16:9 to stretched 16:9, but not that one set of 720x576 samples is higher resolution than another. Am I missing something?

Richard Hunter -->>>

The concept is that the more pixels that are sampled from the CCD the higher the perceived resolution is, regardless of the actual "DV" pixel count. To give an over simplified example I take a high res photo taken from a 35mm still camera and drop it into a DV piece I am editing on my PC. When I cut from the actual DV camera footage to the 35mm shot there is a huge difference in the resolution and clarity of this shot. IT is obviously a much higher qulaity source image. This proves that regardless of the DV compression, it is possible to see more information if the source material is more detailed.

Therefore a 940x480 16x9 source image from the CCD on the XL2 has the potential to look more clear and precise than an image acquired from a 720x480 sample from a source CCD on other prosumer level cameras, regardless of the compression after that stage.

Make sense?

Hmm. Well said there, Marty!

Hi Marty, thanks for the explanation. OK, there are probably other good reasons why the image from 35mm film is clearer than those from a DV camera, but I get what you are saying. Even so, the 940x480 resolution would apply only for a system such as used in the XL2 and not to native 16:9 per se, right? For example, if the CCD is 16:9 aspect ratio and has 720x480 pixels, it would still be native 16:9 but I don't see that it would have higher resolution than 4:3 at 720x480.

Richard

Besides the excellent point made by Marty you also have an
actual increase in resolution: the vertical resolution. Let me
clarify by a short example:

Normal NTSC DV is 720 x 480 pixels.

A fake 16:9 camera that does an anamorphic stretch does the
following:

1. crop the signal to 720 x 364

2. stretch that back out to 720 x 480 (upsampling)

(or it can do the stretch first and then a crop, but that's the exact
same thing)

So you are now working with a 720 x 364 pixel image instead of
720 x 480! Which looses you 116 lines of resolution (which would
be the same if you letterboxed it for example)!

A true 16:9 camera like the Canon samples the image in 16:9
mode at 960 x 480: http://www.dvinfo.net/canonxl2/articles/article06.php

So the only thing this camera has to do is:

1. stretch the signal back to 720 x 480 (downsampling)

In this case you "loose" resolution in the HORIZONTAL (since you
go from 960 to 720 pixels per line). However, the VERTICAL can
stay the exact same.

If you compare this to the faux method you see that you gain the
116 lines of resolution that you lost there.

So you have two things to gain from a true 16:9 camera or a
camera with an anamorphic attachment that records in DV:

1. an increase in VERTICAL resolution

2. a higher sampling resolution which yields a richer image (Marty's point)

This is the exact same thing that happens with a DVD (the image
recorded there is 720 x 480 as well, anamorphic 16:9 or not!).
The increase is in vertical resolution and not horizontal or both.

Ofcourse the best thing would be to not re-sample/scale/stretch
the image at all and get the full 960 x 480 image, but that is just
not allowed in the DV standard (for bandwidth reasons at that
time etc.), so that's not going to happen.

The only thing one can do is go to a HD format for even greater
resolution, but even those sometimes have stretching.

For example, the new Sony camera records at 1440 x 1080 instead
of the full HD 1920 x 1080 signal. What they have done is that
they are recording at a different pixel aspect ratio so that 1440
must be horizontall stretched (upsampled) to 1920 which ofcourse
looses you some resolution. Although it is still (much) more than
960 x 480 in plain SD resolution.


Richard: to answer your question: with such an attachment the
chips will not change and you can argue about resolution. In this
case you will still benefit from my point #1 in the list above (since
you get to keep the full vertical resolution) and point #2 is the one
you can argue about. In my opinion you gain in optical resolution
instead of true pixels like a true 16:9 CCD.

The end result should however be the same with a good enough
piece of anamorphic glass in front of your camera!


I hope this post has clarified some things!

RE: "This proves that regardless of the DV compression, it is possible to see more information if the source material is more detailed."

This statement, at first blush, appears to violate the sampling theorem. A sensor with 720 pixels in its horizontal dimension cannot represent more than 360 cycles per picture width. A sensor with more than that (e.g. the 960 in the XL2) can capture higher spatial frequencies but they cannot be correctly displayed if the image is downsampled to 720. "Proper" downsampling would require that all frequencies above 360 CPW be attenuated below the visibility threshold. If this is not done then those frequencies will appear as aliases. "Proper" downsampling requires a "brick wall" filter i.e. one whose response goes from unity gain at 359.9999 CPW to 0 at 360.0001. Such a beast does not exist. Practical filters must start to roll off gain well below 360 in order to have sufficient attenuation above 360. The wider this so called transition band the easier the filter is to implement i.e. the fewer "taps" it requires or, put another way, the shorter its impulse response needs to be. Impulse response duration is important when working with images because of its effects on the edges of the picture.

So why does 35 mm downsampled to DVD look better than the stuff coming out of our XL2's? I believe that the answer is that in the telecine process the frames are substantially oversampled which allows the interpolation filter to have a narrower transition band. Thus we get closer to 360 CPW, the fundamental limit of the medium than we do with the filter implemented in the camera.

What about 4:3 where there is no downsampling and we can't blame the low pass filter? I'm afraid the answer there is that the camera, though its chips have 720 pixels, is not capable of anything near 360 CPW resolution. This could be caused by MTF limitations in the lens or other optical components (which doesn't bode well for an HD version of the XL series) or by the infamous Kell effect or combinations of the above. I find the manufacturers very disingenuous when it comes to discussions of the resolutions of these cameras (and not just Canon). There's lots more to it than pixel counts! Why won't they show us resolution targets or MTF curves?

To summarize: The absolute limit of the DV system is 360 cycles per picture width. The fact that telecine video looks sharper on DV than XL2 video means that DV is not the limiting factor in the XL2's resolution. So in essence I agree with the quoted statement up to somewhat less than the ultimate limit which DV does impose: 360 CPW.

Synchronious sampling a CCD structure (e.g 720 hor samples for 720 hor pix) is not a nyquist problem. And indeed higher pix counts need to be downsampled with all the low pass filtering problems and limits involved. The basic problem is the optical sampling by the physical CCD structure: the scene is being sampled by 720 (hor) photosensors( simular story is true in vert direction). If this scene contains spatial (horizontal) components which can interfere with the pixalated CCD structure we get optical aliasing which cannot be reduced by whatever filtering on the electrical signal. So optical lowpass filtering (preferable steep) is the only way to go. Consumer cams quite often only have the MTF and/or diffraction limits as optical low pass filtering. Not at all steep and thus introducing alising vs res limits as a trade off. If we got a cam with an infinite number of pix there would not be optical aliasing, and just an ideal (digital) lowpass filter would result in 'perfect' DV samples. The approach on the optical oversampling (a multitude of 720 hor pix) and steep filtering is what happens in 35 mm telecine processing., and this makes the DV pix better.

<<<-- Originally posted by Rob Lohman : Besides the excellent point made by Marty you also have an
actual increase in resolution: the vertical resolution. Let me
clarify by a short example:

Normal NTSC DV is 720 x 480 pixels.

A fake 16:9 camera that does an anamorphic stretch does the
following:

1. crop the signal to 720 x 364

2. stretch that back out to 720 x 480 (upsampling)

(or it can do the stretch first and then a crop, but that's the exact
same thing)

So you are now working with a 720 x 364 pixel image instead of
720 x 480! Which looses you 116 lines of resolution (which would
be the same if you letterboxed it for example)!

A true 16:9 camera like the Canon samples the image in 16:9
mode at 960 x 480: -->>>

Hi Rob. I agree that native 16:9 is higher resolution than stretched 16:9, but what I was questioning was whether it is higher than native 4:3, if both are sampled at 720x480. I still don't really see that it can be so. Maybe your point is that most cameras will not offer both native 16:9 AND native 4:3, and must compromise on one of them? I would agree with that.

Regarding Marty's post, I think the example of comparing the quality of a 35mm image with DV footage is not so relevant. If I compare XL2 and VX2000 4:3 DV footage, I can also see differences in clarity that are obviously not related to resolution.

Even if we talk about sampling 16:9 at 960x480, it is proportionally the same number of horizontal pixels as sampling 4:3 at 720x480. Remember that the XL2 shows a wider view in 16:9 mode, and 1/3 more width than 4:3 requires 1/3 more pixels to maintain the same resolution. So how can we expect any more clarity or higher resolution from a 16:9 image sampled at 960x480 pixels compared with a 4:3 image sampled at 720x480. Even allowing for perfect downsampling (which is another can of worms), I thought the results should be exactly the same (except one is wider).

Richard

An interesting thread to follow. If one of you know the answer, I would be interested to know how the SDX900 acheive to provide the differents aspects ratios. Three 16X9 2/3" with a smaller patch for 4:3, or the same as Xl2 (but bigger CCDs of course)?

Richard: the XL2 offers both native 16:9 *AND* native 4:3

The 16:9 is NOT SAMPLED at 720 x 480, it is STORED at 720 x 480.

That is a WHOLE different thing. The CCD's are sampled at 960 x 480!

That is downsampled to 720 x 480. Again, if you want to strictly
talk resolution the INCREASE is NOT in the HORIZONTAL BUT in
the VERTICAL. You get 480 lines of (original) pixels instead of 364!

So the sampling IS higher and the end result IS better.

You are mixing horizontal with vertical. And yes, you are right
that the field widens so more information is in the horizontal
(which should perhaps yield a higher compression level).

Your comparison to the VX2000 actually has everything to do with
resolution since the sensors on the XL2 use more pixels (which is
whole other thing to talk about...) and the lens is probably sharper
as well. But that's for another thread <g>

Lets assume for a moment that the MTF of the lens is what limits the resolution and further assume that one views at the optimum distance where 1 horizonatal scan line subtends 1/60 degree. If one puts the camera on a tripod, frames a shot and records a few seconds in both 4:3 and 16:9 the image impinging on the CCD block will be exactly the same but the 16:9 horizontal data has to be compressed by 720/960 to fit into the 720 pixels DV allows so that a picture sample which covers 1 unit of width on your fovea in 4:3 covers 1.33 units in 16:9. The 16:9 picture is, thus, 33% blurrier in the horizontal direction but equally sharp in the vertical.

Hi Rob. As I mentioned, I am not comparing stretched and native 16:9, I am trying to compare native 16:9 and native 4:3. The vertical resolution is therefore fixed at 480 (for NTSC) so is not a variable in this case.

Even if there is no downsampling loss going from 960 to 720 samples (which I think is not feasible in real life) my point is that 960 samples for a 16:9 horizontal line is the same resolution as 720 samples for a 4:3 horizontal line, so I don't see how native 16:9 can be described as higher resolution than native 4:3.

Regarding the VX2000 and XL2 images, I am comparing 4:3 video from both cameras, not native 16:9 with stretched 16:9. I believe the resolution of both in 4:3 mode is 720x576 (I am using PAL) and the sensors are using exactly the same number of pixels. As far as I can see, the differences are not related to resolution at all. When you say that the sensors on the XL2 use more pixels, does this apply in 4:3 mode?

Richard

<< I don't see how native 16:9 can be described as higher resolution than native 4:3. >>

Well, strictly speaking, no it is not. But the main point here is that there's no loss of resolution in 16:9 mode, as there always had been in the past prior to the availability of native 16:9 camcorders such as the XL2.

<< When you say that the sensors on the XL2 use more pixels, does this apply in 4:3 mode? >>

Yes, see the comparison chart at www.dvinfo.net/canonxl2/articles/article06.php

It may be getting down to semantics but if resolution means the ability to resolve then there is a loss of horizontal resolution in the XL2 in 16:9 mode relative to 4:3 because the same number of pixels are being used to cover 33% more world in the horizontal direction. If you hang a resolution chart on the wall, frame and focus and capture some video in 4:3 then change to 16:9 without changing anything else then upsample the captured images so they have the same number of pixels vertically (resulting in more samples in the horizontal direction for 16:9) and compare you will get something like this:

http://www.pbase.com/image/37816574

These images are crops from the centers of the captured images and have been upsampled to be 400 x 400 pixels each. The 16:9 sample is on the left; the 4:3 on the right. That the horizontal resolution is better with 4:3 is quite clear from examination of the Group 1 vertical bars. What you get in return for this lost resolution is more picture. Now it is true that we are appreciably better off than in the XL1 where 16:9 was obtained by tossing out lines at the top and bottom of the picture.

I'm not sure I follow what you're demonstrating here. Are you saying that you digitally resized (up or down) the 16:9 image? To what purpose -- just to maintain the same visual aspect ratio? Because the resizing process may account for some of the difference here...

A fundamental difference between 16:9 and 4:3 is that they use the same # of pixels, but the shape of the pixels is what changes. To be a fair test of what is actually being resolved by the camera, I'd think you shouldn't do any resizing of the image, just let one be fat and the other be skinny and let's see what the actual pixels look like.

(btw, I do think your original premise is correct, and that there should be an overall slight loss in resolution in 16:9 as vs. 4:3, due to the 960->720 pixel conversion. I'm just not sure I understand quite what you've done here and whether that reflects it properly).

<<<-- Originally posted by Chris Hurd : << I don't see how native 16:9 can be described as higher resolution than native 4:3. >>

Well, strictly speaking, no it is not. But the main point here is that there's no loss of resolution in 16:9 mode, as there always had been in the past prior to the availability of native 16:9 camcorders such as the XL2.

<< When you say that the sensors on the XL2 use more pixels, does this apply in 4:3 mode? >>

Yes, see the comparison chart at www.dvinfo.net/canonxl2/articles/article06.php -->>>

Hi Chris. I think you are comparing native and stretched 16:9 again, which is not what I was questioning.

For the sensors pixel count in 4:3 mode, your comparison table shows just under 2% fewer pixels for the VX2100. All other things being equal (which I totally accept is not the case when comparing the XL2 and VX2000) I would not expect this difference in resolution to be very perceptible. If I am wrong, then the resampling from 960 to 720 horizontal pixels for 16:9 mode would give a huge reduction in perceived resolution, (notwithstanding the argument already put forward that we can still see more clarity from a high quality source image that has been downsampled to DV resolution). There just has to be a quality hit when going low rez, otherwise the solution to delivering high definition video at low bit rates would be very easy - just downsample it.

Richard

canon's ccd?
 

sorry if this was already asked before - in this case, please send me just simple link to corresponding issue (subject).

who is producer/provider of canon's xl2 ccd?

i read (heard?) before it was panasonic (for XL1), but cannot confirm it. anyone knows?

when i tested both cameras dvx100A and brand new canon xl2 on ibc in amsterdam last september, the look and feel was almost identical - very similar color interpretation, especially when difficult colors are presented (i had special carton wiht bluish green which is my "ultimate" color tester), and the result was very similar if not identical.

so, my question is - is canon's ccd panasonic's one?

thanks,

filip

What deLanghe compares by these transformed images is in fact the angular screen resolution as seen from a fixed distance at fixed picture hight. And indeed the number of cycles/degree is in favor of the (smaller) 4:3 picture if the basic number of pixels/lines is fixed in the images.

Barry,

Fair enough. The original frame grabs are at http://homepage.mac.com/ajdel/FileSharing7.html. A couple of things folks need to think about when viewing these. They are both 720 x 480 which is 3:2. To see them as they would be seen on a TV screen they need to be re-sampled to, respectively 16:9 and 4:3. That's what I did in Photoshop using bicubic interpolation with the final picture heights being the same in each case. Also, when you look at them on a computer monitor you have to be cognizant of the fact that resampling is taking place and that both the algorithm used by the viewing application and the interpolation (if any) done by your graphics card come into play. Photoshop is a good tool for viewing these frames because there is an "actual pixels" mode in which one pixel in the file goes to 1 pixel on your monitor and when scrutinized using the magnifier tools individual pixels are blown up to "tiles" so that the individual pixels in the original can be clearly discerned.

Happy Holidays to all!

Okay, I am officially in the A.J. deLange fan club now... I understand exactly what you're saying, I agree, and I can demonstrate it as well.

Here's an extraction from the XL2. This was an Accu-Chart, which is a high-definition test chart. We shot this exact same chart on the XL2 from a locked-down tripod shot, the only thing that changed at all was the switch on the XL2 from 4:3 to 16:9.

I took the horizontal resolution section and extracted a patch and compared them side-by-side, no resizing or anything.
http://www.icexpo.com/XL2-16x9-vs-4x3.JPG

The XL2 is quite clearly capable of resolving horizontal detail much more clearly in 4x3 mode than it is in 16x9 mode. In 4x3 mode the lines marked 500 are crisp, sharp, and cleanly resolved, and 600 looks pretty good as well. It even did a fair job at separating out the lines marked 700. In 16x9, 600 is not resolved well at all, and 700 turns to complete mush on the right side. I would tend to think the 960->720 downsampling has something to do with it; it would be interesting to see how the FX1 performs on the same chart, seeing as it has 16x9-shaped CCD's with wide skinny pixels (but also 960 of them).

I think I have that shot here somewhere, I'll have to look for it...
(edit: I don't have that shot. I do have an in-camera down-rez of shooting the Accu-Chart as HDV, and recording the firewire output as DV. In that mode, the FX1's horizontal resolution looks basically the same as the XL2's 16x9 mode).

(for reference, the Accu-Chart lists different horizontal resolution numbers depending on whether you're shooting 16x9 or 4x3, to take into account the effect of "TV Lines" of resolution. According to the accu-chart, the XL2 is showing about 450 lines in both 4x3 and 16x9 mode.)

Thought there would be some replies to this by now. Anyway, I'd just like to say thanks to Barry and A.J. deLange for carrying out these tests and posting the results. This is the best way to get closer to the truth.

Richard

Great article in this months DV magazine by Adam Wilt on widescreen and CCD sizes. His comment regarding the XL2's use of 4:3 chips, is that the results are "Just as good" as if the company had used 16:9 chips.

AJ and Barry,

Although I don't understand all of the technical things you are discussing, I do understand what you're saying about the resolution chart results.

I was momentarily taken aback by this apparently proven reduced resolution of 16:9, until I realized that though the result may be technically correct, it is sort of comparing "apples to 1.33 apples" and is inherent to the fact that 4:3 and 16:9 are -- obviously! -- different aspect ratios.

Just so folks don't misunderstand and start saying, "Aha, the XL2's 16:9 sucks after all" please allow me to expand on what I know you already know and, I'm sure, would agree with:

The same subtended arc sees less percentage of the widescreen image in the XL2 than it does of the 4:3 image. Your results compare the horizontal resolution of the full width of a 720x480, 4:3 image against 75% of the width of a 720x480, 16:9 image. So it isn't at all surprising that the 16:9 image looks 25% smaller and resolved fewer lines in your test jpg...less of its width and fewer of its pixels were used in the test.

Without having done any such tests myself, I'm quite confident that if we compare images of equal horizontal or areal percentage, the 16:9 will resolve just as much detail as 4:3, if not MORE...again, since the image aspect ratios and PARs are different, one really needs to compare the whole images, or at least equal percentages of the images, to do a practical comparison.

Please don't get me wrong. We all greatly appreciate the work you are doing and sharing with us. I just didn't want that point to be confused...it briefly surprised me, but I was willing to stop and think it through. However, not everyone might be so inclined. Didn't want anyone going on to misinterpret your interesting findings.

Pete,

See if you agree with this. You have a perfect camera i.e. one in which all that engineering stuff you referred to works at its theoretical limit. It's got lots and lots of pixels in both the horizontal and vertical directions and all its resampling algortithms work really, really well. The camera puts out DV. It's scheme for doing 16:9 is the same as the XL2's. It just takes samples from a wider area in 16:9 than it does in 4:3 and the height from which it takes samples is the same.

You frame a picture of a picket fence in 4:3 such that the vertical extent of the frame just fits the vertical length of the pickets. The pickets are spaced an amount equal to their width and there are 360 of them in the frame. When this image is converted to DV there will be 360 vertical rows of white pixels, one for each picket and 360 vertical rows of dark pixels, one row for each space between pickets.

Now you switch to 16:9 mode. The image captured by the camera now covers 480 pickets and 480 spaces. The picket height is still the same number of pixels. The camera resoves these new pickets as well as it did before because all that has changed is that you are switching more pixels on. But, and here's the heart of the matter, the camera has to down sample in the horizontal direction to the same total of 720 in order to put out DV format. You no longer have just 1 picket or space per column of pixels but rather 1 picket and 1/3 space. Thus the pickets are not as well resolved. In return for having to look at aliased pickets you get to see more of them. To get rid of the aliasing you would have to move in closer so that you only have 360 pickets in the view finder again. This would no longer permit you to capture the tops and bottoms of the pickets.

No, the message is not that the XL2 sucks in 16:9 mode. It is just that it's ability to resolve in the horizontal direction is a little less than in 4:3 for the same level of vertical resolution.

AJ, that's an outstanding "thought experiment!" As before, what you've said is entirely logical and I don't disagree with a word of the experiment. I would just phrase the conclusion a little differently. Let me try again, taking a slightly different approach. See if you guys agree with this, then:

It isn't the XL2's "limitation" per se. What I think you guys are driving towards is that DV 16:9 images are inherently different than DV 4:3 images. They're different geometric shapes composed of differently shaped pixels and you can't really make a generalized comparison of them in one dimension only...16:9 has a 1.2 PAR and 4:3 has a 0.9 PAR. You could conversely say that for a given width, the vertical resolution of 4:3 is only 75% the resolution of 16:9...hence the 360 pixels of "squeeze mode" wide screen in the previous generation of cameras. Thus, one could do your awesome picket fence experiment in the vertical and say the same thing about the XL2's 4:3 that Barry's horizontal experiment causes you to say about 16:9.

Since what we really look at onscreen is a two dimensional image, let's compare 16:9 and 4:3 images of equal area: a 144 square cm screen. The 16:9 image is, simply enough, 16cm wide by 9cm high; the 4:3 image is 13.8564cm wide by 10.3923cm high. Both of them will have (at theoretical limit) 720x480 pixels; the pixels are just shaped differently and thus collectively occupy a differently shaped area. But viewed from the same distance, the images will overall, on average appear equally as sharp because they contain the same amount of image information. The two different geometries will have slightly different strengths and weaknesses, and lead to artifacts under somewhat different circumstances, though...such as horizontal and vertical picket fence tests!

Again, I am not at all saying Barry's experiment is faulty. It is showing specific (valid) results that I think speak to the geometric limits of DV rather than the quality of this or any other particular camera. But, once we can compare 1 apple to 1 apple, then the quality of the CCD block, etc, etc becomes fair game. I wonder...has anyone devised a whole-image "resolved pixels" test? If not, maybe it is time?

Hi Pete. I would agree that shrinking down the 16:9 image will make it a bit sharper, but the main point is that for the same vertical image size and resolution the 4:3 image will be sharper than 16:9 since the 720 pixels represent a smaller width.

I'm not so sure of your point about the artifacts, however. The 16:9 will have downsampling artifacts such as those in the picket fence example. The 4:3 has not been downsampled at all, so it will not. Are you saying that the 4:3 image will suffer from some other form of artifacts that the 16:9 image will not?

Richard

<<<-- Originally posted by Richard Hunter : Hi Rob. As I mentioned, I am not comparing stretched and native 16:9, I am trying to compare native 16:9 and native 4:3. The vertical resolution is therefore fixed at 480 (for NTSC) so is not a variable in this case.

16:9 can be described as higher resolution than native 4:3. -->>>

I don't think that has ever been said. What everyone was saying
was that native 16:9 has a resolution increase over fake 16:9.

You either want 4:3 or you want 16:9. If you want 4:3 then shoot
in 4:3 since it will indeed have more resolution (but not more
sampling) than 16:9 mode.

If you need 16:9 then it is better to shoot in a true 16:9 form than
it is to do a stretch or letterbox since you increase (vertical)
resolution and you loose some horizontal resolution, but you gain
a wider field of view and a higher horizontal sampling.

So yes, you are correct in that the horizonatal "overal" resolution
will be lower in true 16:9 compared to 4:3 on the same camera.
However you get an increased sampling (which might appear as
a higher resolution) and a wider view in return, ofcourse.

Richard,

My point is that both images end up as 720x480. Both will theoretically show up to 360 pickets horizontally. That's it; no more. If you turn the camera 90 degrees, both will show 240 pickets. That's it; no more. It has nothing to do with downsampling, CCD blocks, or glass; it is simply the limit of DV.

So Barry's test was entirely predictable: it compared the full 720 pixel width of a 4:3 image with 75% (540 pixels worth) of the width of a 16:9 image. So the 16:9 image looked smaller and less sharp in that test. If you turned the camera 90 degrees, you could show the same result against 4:3. You could oversample by a billion pixels and use a Cray computer for downsampling...and still not get better results because that's all that DV can give you.

It doesn't matter that it is 16:9 or 4:3. They just happen to be different shapes derived from a grid of 720x480 pixels that are shaped differently...0.9PAR vs 1.2PAR. For anti-aliasing algorithms, maybe DCT (don't know about that), and such, the edges of pixels may be located differently and that may make a small difference in the final image.

Now, if we look at the full width (or height) of an image and our camera is giving us less than 360 (or 240 for height) pickets, then we are starting to talk about the capabilities of our cameras.

I hope that helps clarify.

I agree with what Pete is saying, completely.

It is important to keep in mind that the 4:3 picture is showing more detail in the picture, but is showing less overall picture. The 16:9 shot was showing more, overall.

There's nothing wrong with the XL2's 16:9 mode, I hope people aren't drawing the conclusion that there is! It's a different shape, and as such it's... well, things are going to be different when you're shooting 16:9 vs. 4:3!

About the only thing that could be conclusively drawn is that you shouldn't shoot 16:9 with the idea that you could pan 'n' scan crop down to get a 4:3 extraction, unless you're prepared to have a lower-res 4:3 version. If you want a fullscreen 4:3 image you'll get better results by shooting in 4:3, than you would by extracting a 4:3-shaped patch out of the 16:9 image. (Not that anyone was discussing doing so, but it's really the only conclusive decision I can draw from the test results!)

Yup. Pan-n-scan would suffer, just as "stretch mode" 16:9 suffers. Is it possible we have reached consensus on a topic at DVinfo? How often does THAT happen! Mark your calendars! ;-)

Barry, thanks again for doing testing on real rez charts. If I've missed some links along the way, point me to them, but I haven't noticed too much objective testing posted, like the test you placed in this thread.

Are those who have actually done resolution testing on the XL2 satisfied that in either mode it shoots fairly near theoretical limit? It SEEMS to based on the beautiful videos, but it would be interesting to see more rez chart results like Barry's.

<<<-- Originally posted by Rob Lohman
2. true 16:9 (whatever method)
- resolution and FoV increase in 16:9 compared to 4:3
- 4:3 is lower resolution than 16:9 (that is the whole idea)

-->>>

Hi Rob. Don't want to belabour the point, but what I was questioning was the statement above that has nothing to do with fake 16:9. If this is not what you were saying, then we (probably) don't disagree after all.

Pete, I agree with what you say. I just don't agree that 720x480 16:9 can be higher resolution than 720x480 4:3, which is what I interpreted the quote from the post above as saying.

I also agree that the reduction in horizontal resolution is not any limitation of the XL2 in 16:9 mode. It is a direct result of the DV spec that only allocates 720 pixels even when the width has increased by 1/3.

And by the way, I am very happy with my XL2. :)

Happy New Year?

Richard