How is the size of ccd measured, is it a diagonal meas. or the meas. of one side.

Discussion in 'Professional Video Production' started by steve, Aug 28, 2003.

1. steveGuest

Well the companies specify say a 1/4" ccd or a 1/3" ccd . What are
they measureing? Is it the diagonal? Or one of the sides of the
rectangle? How can you figure the area? There are ccd now on the
consumer camcorders that specify the size and the pixel count and how
many are used for video. But now there is native 16:9 being done and
sometimes there is top pixels above image that get used for Digital
image stabilization and certain types of progressive similation of
video. So how can you conclude what the exact shape of the ccd is to
make conclusion on the size measurement specification given by the
manufacturer?

In other words my point is this: How can you make a comparison of ccd
size from a number such as 1/4", if the actual shapes vary, and the
1/4" is refering to a diagonal measurement?

steve, Aug 28, 2003

2. Richard CrowleyGuest

"steve" wrote ...
Why would the shapes vary? Standard TV is 4:3 aspect
ratio and HD is 16:9
Yes, that is the diagonal measurement.

Richard Crowley, Aug 28, 2003

3. DKGuest

I think what the OP meant was if the 1/4" meant a vertical or horizontal
measurement, how could you tell for sure what the actual size is?

For that matter, 1/4" diagonal at a 4:3 aspect ratio would be a different
size overall than 1/4" diagonal at 16:9

DK, Aug 28, 2003
4. Richard CrowleyGuest

It doesn't mean the vertical or horizontal measurement.
It always means the diagonal. (Unless someone has a
counter-example.)
Now THAT is a good question!
My assumption would be that any dimension is a diagonal
measurement of the equivalent 4:3 portion.

Richard Crowley, Aug 28, 2003
5. Richard MeltonGuest

The specified size of a CCD does not refer to an exact diagonal, horizontal,
or vertical measurement of the CCD, but rather on the lens size that the CCD
is designed for optimum performance. This might be confusing for new users,
but it goes back to the days when imaging devices were vacuum tubes. For
extreme high end video applications, usually the diagonal imaging area of
the tube was 2" or 1 and 1/4". As the technology continued to develop, it
was possible to acquire acceptable video with 1" and 2/3" inch tubes and
later 1/2" tubes. Smaller tubes were used for home and industrial use.
Whatever the size of the tube, a lens had to be designed to properly
position and focus an image on the surface of the tube. The lens became
"typecast" so to speak as to the size of tube it was designed for. During
the changeover from tube to CCD devices, in order to avoid confusion, the
CCD size was specified by which size lens it was designed to work with so
that an end user with a mixture of lenses and cameras would know that a lens
from a 2/3 inch tube camera would work properly with a CCD camera with a
"2/3 inch" CCD, or whatever size the camera and lens size might be.

It is possible to use a larger lens size on a smaller than specified CCD,
but the image area aspect of the lens will not be as specified. In a zoom
lens, the maximum zoom and wide ranges will not be as specified. However, if
a smaller than specified lens is used on a CCD, the image will have a
vignette and/or soft focus on the edges of the image.

Richard Melton, Aug 28, 2003
6. MitchGrossGuest

To expand upon Richard's very lucid explanation, a 1/4" format sensor is not
actually 1/4" in any of it's dimensions; it is in fact smaller. This is true
of all the formats. While a 16:9 2/3" sensor may sound at first to be almost
the same size as a Super-16 mm film frame (which by the way, is NOT 16mm in any
dimension), it is in fact smaller, closer to a 12mm size.

In certain ways these numbers are almost arbitrary, because they measure off a
reference system that is only relative to their sensor size, and larger in
relativity to that too boot. A sensor for 16:9 2/3" is larger than a sensor
for 4:3 2/3", but neither measures 2/3" in any dimension.

Mitch

Mitch

MitchGross, Aug 28, 2003
7. Chris FGuest

To the original poster, to add to what everyone has stated, there is a
standard for measuring, so in short, the bigger the CCD, the better the
camera.

Chris F, Aug 29, 2003
8. steveGuest

Thanks everyone. I would have never guessed the answer.

steve, Aug 29, 2003
9. David WinterGuest

And now, you have the wierdest measurements like 1/4.6"

Perhaps the time has come for this wretched dimension to be standardised?

DW

: Thanks everyone. I would have never guessed the answer.

David Winter, Aug 31, 2003