Canon XL2 CCDs are 4:3. at DVinfo.net

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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, 03:36 AM   #1
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Canon XL2 CCDs are 4:3.

Admin's note: Paul is new to DV Info Net and
therefore may be unaware that this subject has
been extensively discussed here months ago
when the XL2 was first released.


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I went to the canon xl2 camera overview at DVExpo WEST last week, and learned much valuable information. It's probably already been declared, but the canon xl2 does NOT have native 16:9 CCDs!
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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."


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If you take the lens off and look at the CCD, you'll find it's shaped like a 4:3 CCD.
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Admin's note: Actually there are three CCD's; if you
take the lens off and look at the camera head, you're
seeing a prism block on which all three are mounted.
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. 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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Canon chose to go with 4:3 ccds in order to make it's price point of under 5k.
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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).


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They simply have turned off the top and bottom of the ccd, to get a 16:9 signal out of it.
--------------------------------------------------------------

Admin's note: this produces a
native 16:9 image at 960 x 480 pixels.


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To get 4:3 out of the ccd, they mask off the sides of the already smaller area!
--------------------------------------------------------------

Admin's note: this produces a
native 4:3 image at 720 x 480 pixels.


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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.


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Just thought I'd give the heads up.
--------------------------------------------------------------

Admin's note: just thought I'd clear up
these misconceptions. Thanks -- Chris Hurd.

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Old December 14th, 2004, 04:41 AM   #2
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I'm not sure how this is really news - this has been detailed quite nicely already and in much greater detail. See the following:

http://www.dvinfo.net/canonxl2/articles/article06.php

What matters rather more than the size of the CCD block is the resolution and bit-depth which it samples video at. I think you'll find the XL-2 is actually rather a nice camera all things considered.
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Old December 14th, 2004, 05:05 AM   #3
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My point was to address posts like this one:
http://www.dvinfo.net/conf/showthrea...threadid=36277

Which wonders why the XL2 does not perform as well in low light situations (the smaller pixel size on the CCD results in less light being picked up) as well as letting people know the depth of field will probably be deeper on the XL2 than all other 1/3" ccds
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Old December 14th, 2004, 07:03 AM   #4
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That's certainly true, Paul, but I guess most people (me too) will mainly use the (true!) 16:9 mode of the XL2 which means, you use a larger CCD area than in 4:3 mode.

However, you'll never have a really shallow depth of field with such small CCDs. Even the 2/3" chips of ENG cams leave somewhat to be desired in this respect.
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Old December 14th, 2004, 07:29 AM   #5
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First: what does DoF have to do with whether the chips are 4:3
or 16:9 (yes I know the DoF increases in 4:3 mode) versues 2/3"
ENG camera's? There is no pro-sumer camera in this price range
with 2/3", simple.

Second: I'm going to go against this, the XL2 has true 16:9.

Paul, what would be your definition of true 16:9?

Mine is:
Quote:
In true 16:9 mode your field-of-view (16:9) will increase compared to 4:3 mode and the camera will use more pixels to sample your image
Which is exactly what the XL2 and no other (non HDV) pro-sumer
camera in this price range does!

What if canon had chopped of the top and bottom portion of the
*CURRENT* CCD chips to get them into the 16:9 shape, would
that be true 16:9? (that's what the big boys basically do and that
is still the exact same procedure as what the XL2 does).

Canon just got a 4:3 sized CCD since it is CHEAPER.
If I'm not mistaken one of the HDV camera's does the exact same
thing.

Basically there are three ways (chip wise) to get 16:9

1. use a normal 4:3 chip and do a 16:9 stretch in post (loosing resolution and not increasing field-of-view)

2. use a normal 4:3 chip and get a 16:9 rectangle for it. The 4:3 rectangle is *INSIDE* this 16:9 rectangle and uses LESS resolution (this is what the XL2 does)

3. get a 16:9 shaped CCD which does the exact same thing as option 2

All in all the camera really does have true 16:9. And if you are
concerned about resolution. The camera has more resolution in
4:3 mode than most other camera's out there and this only
increases in 16:9 mode, so no concerns there either.
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Old December 14th, 2004, 07:39 AM   #6
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I can't wait to get my XL2!!
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Old December 14th, 2004, 08:33 AM   #7
 
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CCD block size has absolutely nothing to do with DOF. 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.
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Old December 14th, 2004, 08:48 AM   #8
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The smaller the target in any imaging system, the greater the depth of field. Super 8 film has much greater depth of field than 35mm. DV has much greater depth of field than video cameras with larger chips.

The business about the XL2 having greater depth of field in the 4x3 mode is not quite right. To achieve 4x3 the XL2 simply lops off the pixels on the sides. The optics don't change. All the reflected light streaming in through the lens is washing over the whole chip. It's just that the pixels left in the middle display a 4x3 image. Shooting in 4x3 on the XL2 simply means that you're recording less information from the chip.

Many folks find the depth of field in DV excessive. The dinkiest little DV camera you can buy will have more depth of field than you can shake a stick at. The problem is that all that information can become visual clutter...you know...it is harder to get the viewer's eye to go where you want it to.

The point of this is to say that expansive depth of field is something you get by the yard in DV. Finding ways of getting less of it, like using the 20X lens on the XL2, is really nice to know about.
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Old December 14th, 2004, 08:58 AM   #9
 
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I don't think DOF is related to target size, but, rather, the aperture of the optic that was designed for a particular target size. A lens designed for a smaller target size will be smaller and have higher DOF as a result of the smaller max aperture. Note that if you keep the f/number the same, there is no change in DOF.

If what you're saying is right, then the center of a lens would have more DOF than the outer edges. I don't think this is correct.
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Old December 14th, 2004, 09:10 AM   #10
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Quote:
What about 1/3 inch CCD's having more DoF than 35mm film?

Just as the Target Size can vary as in the above paragraph, so can the size of the film stock or the size of the CCD image sensor. If the Target Size in front of the lens is to remain the same when we change CCD sizes, then DoF will indeed change.
Source: The Ultimate Depth-of-Field Skinny
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Old December 14th, 2004, 09:24 AM   #11
 
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The article referenced by Rob Lohman, above, states the following:

"If all formula variables stay the same and the Target Size (CCD) behind the lens changes, then DoF will not change. If the Target Size changes in front of the lens (by changing focal length or len-to-subject distance), then DoF will change."

In the context of this article, "target size" refers not to the detector size, but, to the image of the subject, i.e. target. That's quite different than the detector size.
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Old December 14th, 2004, 09:34 AM   #12
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Are you saying this to not confuse things with your posts Bill or
are you disagreeing that sensor size doesn't matter (compared
to other "sensor" sizes)?
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Old December 14th, 2004, 09:39 AM   #13
 
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LOL...
No, I really don't want to confuse things. This particular issue has been extremely confusing to me, as Jeff Donald will attest. I finally got it straight, tho'. I agree, Rob, sensor size does NOT matter. Image size on the sensor matters.
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Old December 14th, 2004, 09:52 AM   #14
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Well, yeah, but that's basically the same thing since the image size
is targeted to the size of the sensor.

But this also seems to be true if you mount a EOS lens and get
the 7.2 magnification, you still don't get a shallower DoF for
example.
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Old December 14th, 2004, 09:57 AM   #15
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<<<-- Originally posted by Bill Ravens : I don't think DOF is related to target size, but, rather, the aperture of the optic that was designed for a particular target size. A lens designed for a smaller target size will be smaller and have higher DOF as a result of the smaller max aperture. Note that if you keep the f/number the same, there is no change in DOF.

If what you're saying is right, then the center of a lens would have more DOF than the outer edges. I don't think this is correct. -->>>

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?

Just trying to understand the technicalities of it. I want to know if I'll be able to find work arounds in the future. I'm currently shooting my first video movie (did a few on film before that) and the deep DOF is driving me crazy. Just to do a pull focus from an object to an actor sitting at a table, I had to cheat with distances by using a tele focal length in order to crush all the planes together, and then put the object in front of the camera on a stool, several feets from where it should actually be in the scene normally. It works somewhat, but it's a real pain.

Can't wait to try a Mini35 adapter. Only problem for me is the price. But if I could decrease the DOF by using a normal PL to XL adapter and rent a few 16mm cine lenses, I would do it in a heart beat.
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