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Canon XL and GL Series DV Camcorders
Canon XL2 / XL1S / XL1 and GL2 / XM2 / GL1 / XM1.


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Old December 14th, 2004, 10:07 AM   #16
 
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David Lach wrote:
"If it's the lens that determines the DOF, why doesn't putting a 35mm lens with a mechanical adapter in front of the XL2 decrease DOF?"

The answer goes back to the image size part of this equation. With an EOS lens, the magnification factor forces you to mave further away from the subject(target) in order to make it appear the same size on the sensor as with the standard lens(IOW you don't want to overfill the image frame). As soon as you move further away, the DOF increases so that whatever you gained by going to a 35mm lens, you lose by having to go further away. In the end the DOF stays the same.

The reason the mini-35 gives less DOF is because you're imaging a 2D ground glass image at a fixed distance from the lens, without changing the lens to subject(target) distance.
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Old December 14th, 2004, 10:28 AM   #17
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I you set a subject (like somebody's head) focussed, and you want a it at certain size relative to the total picture height (or width), then DOF will be shallower with larger "sensors" (CCD, film, ground glass..), and the total DOF range (near + far distance) will even be constant over a wide range of zoom settings.
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Old December 14th, 2004, 12:55 PM   #18
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Depth of field depends on lens focal length, aperture, focus distance and the acceptable diameter of the circle of confusion. Period. But the smaller the sensor is the shorter the focal length needed to cover it and the smaller the tolerable circle of confusion diameter so that the depth of field (which depends roughly on the square of the focal length and the first power of the circle of confusion diameter) will depend on the sensor size.

The hyperfocal distance is simply (focal-length)/(f-stop*normalized_diameter) with normalized_diameter being the diameter of the circle of confusion nomalized by the focal length. This number is approximately constant (because we want equal final image clarity at viewing size irrespective of the size of the film or sensor which recorded the image). The maximum depth of field is half the hyperfocal distance to infinity when the lens is focused at the hyperfocal distance. At other focus distances the dependence isn't quite so simple but the general principal remains the same.
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Old December 14th, 2004, 01:44 PM   #19
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Quote:
By definition, any CCD block which records in 16:9 is native, regardless of how much of the CCD block is used, or not used. Non-native, refers to obtaining 16:9 thru the use of letterboxing or an anamorphic lens.
Or digital stretching.
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Old December 14th, 2004, 02:51 PM   #20
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Just a quick follow-up, while I warmly welcome all new members to DV Info Net, I would ask for some basic research before stepping up to make sweeping technical assumptions in an open forum, especially when they turn out to be so inaccurate.

Nothing personal to Paul Gnuyen, and not to reflect badly upon him, but I did feel compelled to insert some corrections to his original post (the content of which has been left intact) in order to prevent the casual reader from getting the wrong idea about what's really going on with the XL2's CCD block.

Basically, the gist of it is this:

The shape of each CCD is completely irrelevant -- they could be circular, triangular, oblong, trapezoidal, 4:3, perfectly square, 16:9, star-shaped, macaroni-shaped, hexagonal, octagonal, or some other shape entirely. All that really matters is the TARGET AREA of the CCD, and in this case, the target area of each CCD in the XL2 is in fact 16:9.
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Old December 15th, 2004, 03:13 AM   #21
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A few points:
Quote:
--------------------------------------------------------------
Canon chose to go with 4:3 ccds in order to make it's price point of under 5k.
--------------------------------------------------------------

Admin's note: Incorrect. they choose to go with the
4:3 shape because that's all they could buy (Canon
must buy the CCD's from suppliers as they do not
make their own, and at the time, all 1/3rd-inch size
CCD's are made in a 4:3 shape).
David Castillo, Senior Technical Representative for Canon Video said in two sessions the reason the 4:3 CCDs were chosen were to keep the price point under 5k and going with NATIVE 16:9 CCDs would have brought it over 7k. He used this terminology of NATIVE 16:9 CCDs.

Quote:
Admin's note: Actually yes they ARE native 16:9 CCD's:
for a complete graphical description of what's really going
on, please read my XL2 Watchdog article, "Canon XL2 CCD Block Overview."
As I said earlier, it was specifically said by a canon representative who was on the Xl2 design team, that the Canon XL2 does not have native 16:9 CCDs. Maybe this forum uses a different definition of native, but I'm just reporting what was said at this canon sponsored event by canon people.

Quote:
--------------------------------------------------------------
The skinny is if you shoot in 4:3 on an XL2, you're using MUCH less of a 1/3" CCD than on the XL1, and as such, you'll get a much deeper depth of field!
--------------------------------------------------------------

Admin's note: the difference in DOF really
is not that remarkable -- as the following
discussion reveals.
Whether it is remarkable or not, it is an issue and was discussed at the event. You will get deeper depth of field using the same lenses shooting in 4:3 on an xl1 or xl1s than an xl2.
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Old December 15th, 2004, 03:14 AM   #22
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err that should be "more shallow depth of field"
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Old December 15th, 2004, 04:20 AM   #23
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Like Chris wrote, "native CCD" behavior doesn't relate to the form factor of the CCD sensor. It only means that the readout architecture of the CCD is representative for the system's vertical line number (480/576) interlaced or progressive. So XL2 has a native 16:9 behavier.
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Old December 15th, 2004, 04:52 AM   #24
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Okay, let's get this sorted out once and for all (I hope).

1. yes, the CCD's are not "native 16:9" as in the shape of the CCD's are NOT 16:9. Canon used NATIVE here to indicate the size of the CCD's, not the output signal. So let's use the word native for CCD size, and "true" whether we get the increase resolution / FoV.

2. as Chris indicated the shape of the CCD's has no bearing on whether the signal generated is a true 16:9 anamorphic signal.

3. keep in mind that an anamorphic attachment creates a true 16:9 signal as well, even if the CCD's/camera does not support it (that's the whole idea).

4. the definition of true 16:9 (as in getting a benefit) is an increased resolution in sampling and an increase field of view (fov). Contrary to popular believe, within the DV world true 16:9 does not increase the horizontal resolution (it does increase the horizontal sampling), but the vertical

5. vertical resolution is increase with true 16:9 in DV since the signal is still downsampled to 720x480/720x576. This yields a vertical resolution increase since you get the full 480/576 lines instead an upsampled one

In the end the size of the chips does not matter at all. What
matters is how they get the 16:9 signal and there are three ways:

1. an electronic stretch: this is what the cheaper/most camera's do and you loose resolution

2. using a larger area on the CCD: this is what the XL2 does and increases resolution and field of view (again, CCD shape/size has nothing to do with this)

3. using an anamorphic attachment: this will also increase resolution and field of view

So the only two methods that are true 16:9 are method 2 & 3.

To recap: yes the CCD's in the XL2 are not native 16:9 (ie, the
shape of the CCD's is 4:3), but the signal generated is full 16:9
anamorphic so it is "true" 16:9.
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Old December 15th, 2004, 07:10 AM   #25
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Sorry Rob, but even "native CCD's"(in your definition) only have a 16:9 readout area (just like XL2) but the global CCD structure has overhead pixels ( just like all CCD's have). So, a 16:9 shaped CCD doesn't exist. Only a 16:9 shaped readout area CCD does exist
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Old December 15th, 2004, 07:15 AM   #26
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Andre: that would be even better! But I could've sworn that
companies claim they are using native 16:9 (shaped) CCD's....

Ofcourse it still doesn't change anything in the story (as you know).
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Old December 15th, 2004, 10:25 AM   #27
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Hi Paul,

Quote:
David Castillo, Senior Technical Representative for Canon Video said in two sessions the reason the 4:3 CCDs were chosen were to keep the price point under 5k and going with NATIVE 16:9 CCDs would have brought it over 7k. He used this terminology of NATIVE 16:9 CCDs.
David and I were telling you the same thing. I stated that 1/3rd-inch CCD's did not exist in the 16:9 shape (they would have to be developed). He stated it would have been too expensive (they would have to be developed). Both of us are saying there was no such thing as a 1/3rd-inch CCD in the 16:9 shape available for the XL2. My take was that Canon would need to have them OEM'ed. David's take was that they could have had them made but it would have been too expensive. Either way it's the same thing: there was no such thing as a 1/3rd-inch CCD in the 16:9 shape available at the time for the XL2.


Quote:
As I said earlier, it was specifically said by a canon representative who was on the Xl2 design team, that the Canon XL2 does not have native 16:9 CCDs. Maybe this forum uses a different definition of native, but I'm just reporting what was said at this canon sponsored event by canon people.
Well, it certainly is no secret that Canon USA's marketing division is quite frequently its own worst enemy. You've just provided a perfect example of this problem. Fortunately for Canon, there are people like myself and many others on this board who at least attempt some degree of diligence by following in the wake they create and trying to repair their own self-inflicted damage. This thankless job is done for the sole purpose of providing our readers with the most accurate technical information possible, in order to aid their selection and proper use of the tools of the DV trade. Sadly there are occasions where there is a conflict between what we tell you and what a manufacturer tells you. That doesn't happen very often, but when it does, it's definitely in your best interest to believe us over them.

Canon USA does not make the XL2. The camera is made in Japan. Canon USA does the marketing and selling for a chunk of North America, and sometimes they know what they've got and sometimes they don't. It's really too bad that I can't be around to rescue them from every instance of bad semantics, but what you were told with regard to "not having native 16:9 chips" had more to do with their SHAPE than anything else. Of course the XL2 produces native 16:9 digital video. And as I've previously stated, the shape of each CCD is completely irrelelevant to its actual target area. It could have triscuit-shaped CCD's but still give you native 16:9 from its actual target area. It could have 8" by 10" size CCD's but still give you an actual target area of only 1/4 inch.

Quote:
You will get deeper depth of field using the same lenses shooting in 4:3 on an xl1 or xl1s than an xl2.
Paul, I understand that the original intent of your post was to point out that the smaller physical size of the XL2 CCD's target area yields the equivalent of a 1/4-inch CCD when shooting in 4:3 mode. You are correct about that and there is no argument here. What I'm taking issue with is, why complain about the lack of a shallow DOF with 1/4-inch chips when that lack is already present at 1/3rd-inch. In other words, my point is that you're really not gaining much DOF control by going from 1/4-inch to 1/3rd-inch. Neither size is good for achieving shallow depth of field. If you want shallow DOF, you need to use the proper tools to create shallow DOF. In the case of the XL2, that would involve the rental of a P+S Technik Mini-35 converter and the appropriate choice of 35mm motion picture lenses. Now there's your shallow depth of field.
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Old December 15th, 2004, 02:46 PM   #28
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Regarding "native 16:9" and all the confusion and all the definitions...

May I humbly submit that "a difference that makes no difference, IS no difference"? I mean, who cares whether it's technically this or technically that, as long as the picture being delivered to the frame is full resolution?

The XL2 delivers full resolution. So does the PDX10. So does the FX1. The XL2 and PDX10 use 4:3 CCD's, the FX1 uses 16:9 CCD's... but who cares? You're still getting the full resolution, and that should be the determining factor: do you get the full resolution of the video frame?

On a camera like the XL1 or VX2000 or whatever, you don't get the full resolution, you get an electronically-stretched image that doesn't provide full resolution. Let's make that the dividing line: do you get full resolution or not? If you do, it's "true" or "native" 16:9. If you don't, it's "fake" 16:9.

If you want to pick on the XL2, say it's a 1/3" camera in 16:9 mode and a 1/4" camera in 4:3 mode. But that has nothing to do with the "native" or "true" 16:9 discussion.
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Old December 15th, 2004, 03:16 PM   #29
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Barry, what do you meam by "full resolution"? I first suppose we are talking about vertical resolution. Further on, do you mean 480/576 lines with active video? Then also uprezzed pics have ""full resolution". In all cases whether it's uprezzed video or native, there is vertical aliasing and vertical resolution limitation. The only difference is that that besides the optical aliasing (straddling...) and resolution limitations you get additional aliasing from the in camera uprez. So I thinkyour "full resolution" is as fuzzy as the "native" approach.
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Old December 15th, 2004, 03:27 PM   #30
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Just call it 960 by 480. Nothing fuzzy with that, right?
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