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-   -   XL2 CCD block overview (https://www.dvinfo.net/forum/canon-xl-gl-series-dv-camcorders/28870-xl2-ccd-block-overview.html)

Chris Hurd July 13th, 2004 09:01 AM

XL2 CCD block overview
 
Several threads are already branching off into separate discussions about the XL2's one-third inch CCD's and how those chips are doing native 16:9 video. I've written an article with graphics which should help explain it:

Canon XL2 CCD Block Overview.

Please discuss it here, for ease of navigation for folks looking for it later! Thanks,

Steven-Marc Couchouron July 13th, 2004 09:43 AM

Thanks Chris for a very informative article which confirms what I had speculated.

Of course we'll have to judge by the image quality itself, but the fact that it uses less of the 1/3" CCD sensor doesn't seem like a good thing, resulting in narrower FOV, longer DOF and, possibly, less low-light sensitivity.

This is particurlaly true for the 4:3 mode.

Richard Alvarez July 13th, 2004 09:55 AM

Heated argument going on here at the shop. The boss says the old way of 16x9 on the Xl1 was a simple mask off of the 4:3 ccd. I am pretty sure Canon used some sort of algorithm to get 16:9 rather than a simple mask. Please explain the difference in 16;9 methods from the old Xl1 to Xl2. He is unconvinced that higher pixel count in a smaller target area will result in greater definition overall.

Guess we'll have to wait for Adam Wilt to give us the lowdown?

Rob Lohman July 13th, 2004 10:03 AM

Well your boss is basically right. It did you a "mask" and then
electronically stretched the footage back to full height.

On Chris' page you can clearly see how the new system increases
resolution. Look at the 4:3 rectangle in the middle. This "little
square" still contains *more* pixels than the old one does on the
XL1S. So the "new" way of doing 16:9 extends the range
horizontally by two columns (left and right).

The pixels in these columns get ADDED to the 4:3 image which
yields a higher resolution image.

However, both options do increase focal length on lenses a bit
due to the way Canon is using the CCD's. I'm not sure how DoF
will respond to this...

Boyd Ostroff July 13th, 2004 10:23 AM

It's nice to see that they've optimized the design for 16:9 video and are using the full chip width. You'd think that 4:3 would suffer and the active area must be closer to a camera with 1/4" chips. Bu t this should send a clear message to all those people who question the need for 16:9, looks like Canon's vote has been cast; we know what their priority is.

With the native 16:9 and progressive scan the results should be terrific (do we know for sure that it's real progressive BTW?) Will be fascinating to see some user reports as to whether this design has some of the problems of other high pixel count camcorders, like increased vertical smear.

Dan Uneken July 13th, 2004 11:39 AM

Rob,

The 10% decrease in image area will increase dof accordingly in my opinion.
Good for P+S.

What totally baffles me is why they have those non-firing pixels on the chips anyway. Or am I missing the point altogether?

Steven-Marc Couchouron July 13th, 2004 11:45 AM

Because if they did use them in 4:3 mode, that would change the focal length of the lens when you switch modes, which wouldn't be very practical. At least that's my guess...

Rob Lohman July 13th, 2004 11:45 AM

I can think of two reasons:

1) this is some standard sensor and it would've cost more to make one with those pieces chopped off

2) it is for a future extension to the XL2 line like HD?

The current 960x720 is pretty darn close to the standard HD
resolution of 1280x720. Who knows what kind of chips are
really in that camera. Then again, it just are 960x720 chips
and they put em in due to possibility 1 above.

Steven: I think he is asking the question why something is there
that is not used at all. Most manufacturers probably would just
have said the chips where 960x480 instead of 720 pixels. The
question as I saw it was why they aren't chopped.

Steven-Marc Couchouron July 13th, 2004 12:01 PM

Maybe they are there so that the DVinfo whizzes in Alternative Imaging can develop special software which could make them active ! :-)

Russell Newquist July 13th, 2004 12:19 PM

I ran the math on the CCDs. If they're using 1/3" CCDs, then masking out the 16:9 and then masking that out to get 4:3, then the 4:3 image area measures exactly 1/4" diagonally. So it should behave exactly the same in terms of depth of field, etc.

Somebody also mentioned in another thread that the higher light requirements vs. XL1s was probably because of high pixel count, but I don't think so - I think it's because they're using a much smaller portion of the CCD on the XL2. This should result in a much sharper image, given the huge increase in active pixels, but it would give it trouble in low-light situations. You'll probably also have to relearn all your f-stop, shutter speed, and filter settings to readjust to the new CCDs.

Unless you specifically need low-light shooting, I'd take the tradeoff any day.

Rob Lohman July 13th, 2004 12:24 PM

Quote:

The three CCD image sensors are specifically designed to capture as much image detail as possible and for shooting under extremely low light conditions. In super low light, the XL2 captures crisp and clear digital data. Under extremely bright conditions, the XL2 greatly reduces vertical white streaks and smears

Russell Newquist July 13th, 2004 12:32 PM

Rob - I was referring to the post by Boyd Ostroff here where he states that the XL2 is rated at 5 LUX which is supposedly less than the XL1s. I can't find anything to confirm or deny this, but if it's true, it's almost certainly the CCD size that's responsible, not the high pixel count.

Dustin Cross July 13th, 2004 02:39 PM

Aloha,

If the CCD is 960x720 then I would think Canon in planning to make this an 720 HDV camera in the future.

A 960x720 CCD gives you an anamorphic squeezed 1280x720 image.

1.33 x 960 = 1276.8

Seems like it could be done with a software upgrade.

Russell Newquist July 13th, 2004 02:46 PM

It depends on how they're doing the masking to crop it down to 16:9. If they're doing that all via software or by just "turning off" the other pixels, as has been guessed, then yeah, they probably could do it with a software upgrade - AND a special animorphic lens attachment.

If they've physically masked off the chip somehow, which they may have done to prevent damage to the turned off areas, then a simple software fix wouldn't do it.

This also assumes that the onboard electronics are powerful enough to process a 960x720 realtime video stream.

Boyd Ostroff July 13th, 2004 04:01 PM

<<<-- Originally posted by Russell Newquist : I ran the math on the CCDs. If they're using 1/3" CCDs, then masking out the 16:9 and then masking that out to get 4:3, then the 4:3 image area measures exactly 1/4" diagonally. -->>>

I have not tried to run the math, and it may not make much difference in the end, however your base assumption is wrong. 1/4" ccd's do not measure 1/4" diagonally, these are nominal sizes with no linear relationship. The image diagonal of a 1/4" CCD is 4mm and a 1/3" CCD has a 6mm diagonal. Just looking quickly, I'd say your logic won't hold up since .33/.25 = 1.32 while /6/.4 = 1.5.

See my post at the very bottom of this page for more info on CCD size. If you look at the specs it may give actual measurements, for example the PDX-10 specs say 3.8mm (1/4.7 type) CCD. The manual for the VX-2000 just says 1/3 type CCD however.

Aside from the details though, your point is valid IMO.

Jeff Donald July 13th, 2004 04:19 PM

Smaller chips yield greater DOF if the image size (subject) is kept the same. Usually we try to keep the subjects head the same size (no mater what size camera we use) so the smaller chip camera needs to use a wider angle of view (wide angle lens) or move back (increase camera to subject and DOF increases). If it doesn't matter the subject is bigger on the smaller chip, then DOF will be the same.

Gints Klimanis July 13th, 2004 05:11 PM

>What totally baffles me is why they have those non-firing pixels on the chips anyway. Or am I missing the point altogether?

CCD yields may be greater if a manufacturer can programatically adjust the CCD "crop" .

Jeff Donald July 13th, 2004 05:24 PM

Non-firing pixels are used to establish a black level or zero voltage. the camera needs to know what true black is to make certain adjustments and set various levels.

Steve McDonald July 13th, 2004 05:35 PM

In my measurements of the 4:3 sensing area of the XL2 CCDs, the actual diagonal size comes out at .238 inch, or a bit smaller than 1/4-inch or .25-inch. In 16:9 mode, the diagonal measure is .32-inch or slightly less than 1/3-inch or .333 inch. These were taken using the CCD graphic image posted by Chris. The actual size of the sensing areas would likely be even less, as the CCD sizes are only nominal and correspond to the sensor sizes inside the old tube cameras. The smaller pixel size and overall sensing area obviously would decrease the low-light performance, unless improvements in CCD sensitivity are present in the new sensors.

According to the lens magnification increase ratios Chris posted, between the XL1 and XL2, the XL2 in 4:3 mode would gain 35% in magnification. So, if the old 16X lens from the XL1 was used on the XL2, it would produce 21.6X. So actually, the older lens is more powerful than the new one, that gives 20X. In the past, beginning with the L-1 in 1991, it has been almost as expensive to buy a separate camera body, without a lens, as to get a camcorder kit with a lens included. If a lenseless XL2 were offered at a fair reduction in price, quite a few current XL1 owners might choose to use their old lenses on it and save some money. Of course, the new lens has some significant improvements in features and what seems to be a better arrangement of controls.

I haven't noticed anything about still picture captures on the XL2 yet, although with the large amount of information flooding the site, I may have missed something. With 30p, the option of recording footage usable for both motion video and sharp still captures of moving subjects is greatly enhanced. There is still a horizontal pixel offset (pixel-shift in Canon terminology), but the vertical offset that the XL1 CCDs have, is eliminated. This should increase the camera-direct resolution and images captured on a memory-card, straight from the camera, could have a greater pixel size, than the 640 X 480 maximum of those grabbed later from tape footage. This is assuming that the XL2 is set up to do this??

Steve McDonald

Jeff Donald July 13th, 2004 05:38 PM

The 16x referred to is the zoom ratio from the widest setting to the longest setting. For example, a zoom from 10mm to 100mm is referred to as a 10x zoom. It does not refer to the magnification factor etc.

Barry Goyette July 13th, 2004 05:45 PM

Steve

From the Canon website

Number of Recording Pixels
approx. 460,000 pixels (962 x 480) x3 CCD, 0.289" diagonal
approx. 350,000 pixels (720 x 480) x3 CCD, 0.236" diagonal

The new lens is a 5.4 to 108mm (20x ...or tele is 20 times the widest zoom setting). The old lens is a 5.5 to 88 (16x). So the new lens is substantially longer.

Damn, jeff beat me to it. He always does that.

Barry

Steve McDonald July 13th, 2004 06:41 PM

Barry, the new lens may have a longer zoom range, but since the CCD sensing area of the XL2 is smaller than that of the XL1, the magnification effect at full zoom should be greater on the XL2 than on the XL1. In fact, Chris posted specs that showed that the magnification increase when using the old 16X lens of the XL1 on the XL2, was 35%.

Something doesn't add up with these lens specifications. The new lens that comes with the XL2 is labeled as 20X, so that's obviously all the more it delivers on the new camera. If the old lens gives 16X on the XL1, that has a larger CCD area, it has to give more magnification when used on the XL2. But yet, as you stated, the zoom range of the old lens has a shorter zoom ratio from wide to tight?? Is there some other variation in the relationhip between the lenses and CCDs of the two cameras, that I'm missing?

Steve McDonald

Barry Goyette July 13th, 2004 06:58 PM

Steve,

The 20x and 16x designations on a lens do not refer to the magnification, or length of the lens, only to the relationship between the widest setting and longest (or most telephoto) setting..so theoretically a 20x zoom could have a 1mm-20mm range, and not get very "telephoto" at all.

That said, if you look at the specs I copied into my last message, you will see that the new lens has a maximum length of 108mm versus the older lens which has a length of 88mm. The longer the lens the narrower the angle of view, thus the higher degree of "magnification. Yes the 16x lens is effectively "longer" on the xl2 than it was on the xl1s, but the 20x is longer still.

Barry

Steve McDonald July 13th, 2004 08:22 PM

Barry, I'm getting redundant here, but if the new lens is 20X and is longer than the old lens and the old XL1 lens has a 35% increase in magnification when used on the XL2, then that would mean that the magnification effect of the new lens would be much greater than that of the old lens. Just what would be the magnification of the new lens on the XL2?
Or is there any way that magnification, as a separate specification, can be simply expressed for any camera/lens combination?

Since most ordinary camera users interpret zoom range to be the same as the magnification effect, this would mean there's been a great general misunderstanding of how much magnification they're actually getting with various cameras and lenses. It would seem that videocamera manufacturers would establish a common magnification measuring standard, probably in relation to 35mm film image size, as well as giving the zoom ranges of the lenses. Of course, the great variation of the sizes of film prints and video screens, further complicates this.

How about picking a 35mm print size and relating it to a video screen size, to establish the magnification standard? Or forget the 35mm film size and just relate the magnifications of all videocamera/lens combinations to the size of a video screen a subject of a certain size fills at full zoom, when shot at a certain distance. Such a magnification value could acquire a simple recognition, that wouldn't need any other specifications to accompany it.

In fact, why just talk about some unspecified standards committee doing something like this? I'm going to set up such a magnification measuring standard myself, using as many cameras and lenses
on which I can get my hands. The magnification values I'll produce will be in numbers such as "6" or "8.5" or "20".
I'll state the arbitrary screen size, subject size and shooting distance I selected and nothing more should be needed to establish relative magnification power ratings.

I'll call them the "MX" ratings. These numbers could be easily used to compare the magnification capability of any camcorder and lens with any other. I'll experiment and choose screen and subject size and distance that will produce MX numbers that will come as close as possible to matching the familiar "X" ratings of the zoom ranges of the lenses. But, I would expect that with some camera/lens combinations, the MX numbers would be somewhat different.

Whatever anyone does in this regard, there needs to be more simple and less confusing specs and explanations of them, regarding lens capabilities on different cameras.

Steve McDonald

Jeff Donald July 13th, 2004 08:40 PM

Steve, don't reinvent the wheel. In 35mm still photography a 50mm lens is considered "normal" because the image it produces is roughly the same angle of view and objects appear to have 1X magnification vs. the actual scene. So a 600mm lens in 35mm photography is said to have 12X image magnification (don't confuse image magnification with zoom ratio) because 600 divided by 50 equals 12. The normal focal length is approximately the diagonal of the image plane. The diagonal for 35mm film is about 43mm. I hope this helps in you quest for determining magnification factors.

Steve McDonald July 13th, 2004 08:58 PM

Clarification of my "MX" Ratings
 
After reading some recent posts, I realize I should make it more clear about the "MX" ratings for measuring the magnification power of camera/lens combinations that I proposed on my last message.

As others have pointed out, "magnification" can be an ambiguous or relative term in regards to videocameras and lenses. However, with the MX ratings I propose to do on various cameras and lenses, the magnification measurement would be based on an absolute standard.
Each camera/lens combination would be rated using the same size subject at the same shooting distance and the results displayed and measured on the same size screen. This way, each camera and lens could be compared to any other, regarding how much they magnify subjects, at full lens zoom. This may seem too simple to please lens Gurus, but it is a missing rating specification that I believe is needed.

The zoom range and CCD sizes wouldn't be a part of figuring the MX rating. Neither would the high end of the
Xmm to Xmm measurement of the lens. The only thing considered for an MX rating number would be how large the subject is made to appear on a video screen, under identical shooting circumstances, as I described.

Steve McDonald

Barry Goyette July 13th, 2004 08:58 PM

Steve

I think there are several ways that the industry has tried to designate "magnification" in terms that people can understand. One has been to relate the relative zoom setting to the 35mm slr lenses that many of us are familiar with. Chris has given conversions somewhere here today, and I think canon has also referred in its literature to the new lens being something like a 1436mm lens on a 35mm camera.

The simplest way to is to note the relative length of a lens. A lens that is twice as long would have twice the magnification and half the angle of view, given identical viewing area dimensions (CCD, film, whatever).

If what you are looking for is a hard and fast number, there is one.The correct term for what you've been calling magnification is ANGLE of VIEW...because this is a much more precise way of describing what is going on. Most lens specs will refer to angle of view, although I'm not sure that I've ever seen it on a consumer video lens spec sheet.

Hope this helps. Cause I'm off to dinner!!

Barry

Rich Lee July 13th, 2004 11:56 PM

all this is great, love the idea of shooting in 16x9. my only question right now is how the hell does it get on the tape? can a dv tape hold a 960x480 frame? im confused....

Chris Hurd July 14th, 2004 12:43 AM

You guys are giving me a headache. Plus it's 2:45am.

Didn't y'all see my Lens Guide chart at http://www.dvinfo.net/canonxl2/articles/article04.php?

Compare that data with the chart on the original XL1 Watchdog at http://www.dvinfo.net/canon/articles/article58.php.

I need to add the new 20x to the old XL1 / XL1S chart.

Fields of view are tighter on the XL2 than the XL1. That's all it boils down to really, but Jeff is the optical science teacher here, not me.

G'night,

Steve McDonald July 14th, 2004 02:27 AM

Thanks for the Education
 
Thanks indeed, to Barry and Jeff for finally getting me to understand some basic things about lens specifications and performance, that I should have known before. As I mentioned previously, I believe I was in the majority of video users, who don't grasp the full meaning of "zoom range" and confuse it with magnification power, or more properly, "angle of view".

Steve McDonald

Steve McDonald July 14th, 2004 02:39 AM

XL2 CCD Performance?
 
Has Canon made any statements about improved CCD performance with the XL2?
With the greatly increased pixel numbers and their reduced size, relative to those of the XL1, as well as a smaller CCD sensing-area, I wonder what the low-light performance will be?

When Sony introduced the VX2000 and the VX2100, they made a big issue about how much more sensitive their CCDs were and promoted their increased low-light capabilities.

If Canon uses new CCDs that have similar increases in sensitivity, this might more than offset the effective size reduction.

Steve McDonald

Rob Lohman July 14th, 2004 05:18 AM

Steve: as quoted previously by me:
Quote:

The three CCD image sensors are specifically designed to capture as much image detail as possible and for shooting under extremely low light conditions. In super low light, the XL2 captures crisp and clear digital data. Under extremely bright conditions, the XL2 greatly reduces vertical white streaks and smears
It is all in the specs! There is also a new thread specifically on
this topic. So perhaps we need to continue to discuss the low
light capabilities there? click here for thread

Rich: I've also explained this a couple of times. But to get my
most detailed explenation on true versus fake 16:9 and how
this is stored, click here to go to that post

Rich Lee July 14th, 2004 09:20 AM

ic, i hadnt seen an explanation on how the xl2 did 16x9 till now, sorry.

so from what it sounds like, the xl2 will do a squeeze, much like an anomorphic to get a 16x9 image?

ok, thanks for the info. cant wait to see some images from the cam, all very exciting!


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