Oversized CCD chips

[Peter A. Smith]

Hi everyone,

I was just looking over the camcorderinfo first impression review and in there is a statement that the XL2 is using 3 oversized chips in creating the "native" 16x9 in the camera.

http://www.camcorderinfo.com/content/Canon-XL2-First-Impressions-Camcorder-Review.htm

Then I read a person in another forum who says he slightly tested the camera and commented: "the chips are new and native 16x9 as they used larger chips to start and so the 4x3 mode is the the same size as before"

According to this info it seems the actual CCD chip size is not 1/3" but larger and by cropping down for 4x3 it's 1/3".

From the specs alone a few would assume that the chips are 1/3 but when cropped for "native" 16x9 and 4x3 that the used size is 1/4 or less.

My curiosity is stirred. Does anybody have any info or heard anything about oversized chips in the XL2?

[Chris Hurd]

Hi Peter,

Thanks for your interest. What you want to do is look over my XL2 CCD Block Overview. Then, if you have any questions about what you read there, just post 'em to this thread, which discusses the article. Hope that helps,

[Don Berube]

Hi Peter,

The CCD's of the XL2 are not oversized. Trust me on this one.

The XL2 uses three (3) 1/3" CCD's, each containing 680,000 pixels. The XL2 uses two different "target areas", depending upon whether you set it to 4:3 or 16:9, which are pulled from within the 1/3" CCD. The largest target area used from within the 1/3" CCD is 960x480 (when in 16:9 Aspect Mode), which is not using the entire surface area of the 1/3" CCD.

Rather than going into this all over again in detail for you, let me point you to the facts. Chris has already done a decent job at drawing this all out at http://www.dvinfo.net/canonxl2/articles/article06.php

Please take the time to read the article carefully and thoroughly. All of the information you need to understand how it is done is contained within the article.

Here's something for all to consider: Regardless of the size of the actual surface area used in the CCD, the truth is in the image output. Period. You need to see the footage which has been shot with the XL2 so far and then decide whether it will fill your needs or not. Canon has been very upfront on how they are achieving the aspect ratios and there is no smoke and mirrors being deployed. This is certainly 'new technology' as far as CCD's go, at least it is for Canon. There is a great degree of resolution and detail in the output of the XL2, which is significantly more resolute and more sensitive to light than previous models. It is simply yet another way of creating a high quality digital video image. Some manufacturers prefer to crop & stretch, some prefer to electronically interpolate. Other much higher priced DVCam platforms use true 16:9 chips. Regardless, look at the image output and then decide which you prefer and move on and shoot something. Rent if need be.

- don

[Peter A. Smith]

Thanks Chris and Don for your quick replies and for this great site.

Yeah those are the only sources I've read that ever commented about "oversized" chips which runs against what info you guys have. That's why I need at least 3 references to have me even consider something as possibly factual.

My curiosity stems from my experience with the PDX10 which happens to get 16x9 the same way the XL2 does. In that camera the 16x9 IMHO outputs better images than its bigger brother the PD150 in certain conditions (especially 16:9). Sony says the PDX10 chips are 1/4.7. Yet, learning from the threads here, I learned that the actual chip area used is reduced, but that doesn't stop the PDX10 from being one of the best buys out there still.

No matter what the chip size, I do look forward to the XL2 reviews and hands on accounts (even though it is out of my price range).

Peace

[Dan Vance]

I think a lot of this "oversized chip" confusion stems from an error on the Canon spec page which says the diagonal in 16:9 mode is .289". Since this is outside the focal plane diameter of the Canon lenses (it's about .240"), this would cause serious vignetting if it were true. Once we know the true measurements, it will all make more sense.
Hopefully Canon will update/fix that page soon.

[Barry Goyette]

Dan...

Where did you get the information that the image circle of the Canon lenses is .24 inches? I've never heard this before, and although I've never known canon to publish the image circle dimensions for its xl series lenses, I would assume that that number would be something slightly larger than .33.

Thanks

Barry

[Chris Hurd]

Hi Barry

It's on the Canon XL2 Specifications page, scroll down to 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

Gotta be a typo there.

[Boyd Ostroff]

No idea about image size, but don't confuse those chip sizes with actual diagonal measurments. They are nominal sizes that go back to the vacuum tube days - see http://www.dpreview.com/news/0210/02...ensorsizes.asp

Standard 1/3" 4:3 CCD's are supposed to have a 6mm diagonal measurement. So 6mm x .03937 = .23622 inches. I think that was his point, as reinforced by Chris.

[Luis Caffesse]

Barry,

Hope you don't mind my jumping in to attempt an answer to this one. I've been emailing Dan on this topic all day, and he's probably tired of hearing about it.
:)


The image area of a 1/3" chip is roughly around .216 inches (or .236 inches depending on who you talk to).

Check out this explanation on Edmund Optics site:

Section 4.3 CCD Sensor Size

Either way, it wouldn't make sense for the image circle of the XL lenses to be any larger than .240 inches, seeing as they are made for 1/3" chip cameras.

Hope that helps.

-Luis


EDITED TO ADD:
Damn you guys all post quickly!

[Barry Goyette]

Luis

Damn...you beat me to it...but I'm going to post my post, and add some hyperbole to it as well.


Ok, Dan, Chris, everybody....stop the presses. I just did a little calculation, based on the spec sheets included with my lenses...Dan, you were pretty close....Canon refers to the 1/3" image size as 3.6x4.8mm. I did a rough conversion and that comes out to a diagonal of .236. Ok...now I think that this is not the image circle measurement that dan is referring to, but the otherwise unpublished sensor size of the xl1s.

So if I'm not hallucinatin', then the depth of field worry warts, have nothing to fear about this sensor, as the 4:3 size on the new sensor is the same.... .236.

Regarding the image circle though, my guess is that it is significantly larger than the .236 diagonal (this would be indicated by canon's ability to utilize a .28 16:9 sensor area) typically lenses project a circle much larger than their intended imaging size...to minimize distortions and vignetting near the corners.

What I'm curious about is why anyone who should know this information (at canon) hasn't corrected all of us bemoaning the new sensor size. (where's jan crittenden when you need her--i know wrong company). If this information is correct...then the xl2 is also a "true, or native" 16:9 camera as well.


Barry

[Chris Hurd]

Nice link there, Luis. They're simplifying things a bit, but there's a pretty important thing to note: "The nomenclature of these standards dates back to the Vidicon vacuum tubes used for television, so it is important to note that the actual dimensions of the chips differ."

In other words, the size usually assigned to a CCD is not a measurement of its diagonal, but rather it's the diameter of a circle (tube size) that it would fit into. CCD's commonly referred to as 1/3rd-inch, 1/4, etc. are actually quite a bit smaller than that even.

[Luis Caffesse]

"the 4:3 size on the new sensor is .236"

Barry,

The chip itself has a diagonal of .236 inches.
BUT, the image area used by the XL2 would have a diagonal closer to something like .17 inches in 4:3 mode.
The entire chip is not being used.

In 16:9 mode, it seems that the XL2 has an active image area of .211 inches, slightly less than what you would expect from a 1/3 inch chip (which makes sense).

"this would be indicated by canon's ability to utilize a .28 16:9 sensor area"

I think the point you may be missing Barry is that it seems that the specs on Canon's site are wrong. You cannot draw any conclusions from those specs, as they don't make sense.

If the sensor area were actually larger than .240 inches, then the old XL lenses would show significant vignetting in 16:9 mode.

-Luis

[Barry Goyette]

Luis..

see chris's post above...specs from canon. Now why would they have posted the pixel and area measurements together if they weren't referring to effective areas?

Barry

[Luis Caffesse]

"see chris's post above"

Yes Barry, and right underneath those specs Chris wrote, "Gotta be a typo there"

The XL lenses were made to work with 1/3" chip cameras.
We've already gone through it, and we all agree that the diagonal image area on a 1/3" chip is .236 inches.

So, the image circle of a 1/3" lens is made to cover .236 inches, and maybe a little more for wiggle room.

If the 16:9 area on the XL2 actually measured .289 inches, then you would see vignetting on the sides when using the old XL lenses.

Basically, the specs on the Canon site are wrong.
We know that because the old lenses work on the XL2.

-Luis

PS.
To clarify, it is the DIAGONAL that is wrong on Canon's specs.
The Pixel count seems to be correct.

[Chris Hurd]

Somebody call the Product Manager!