Steve's Digicams Forums

Steve's Digicams Forums (
-   General Discussion (
-   -   CCD and CMOS, Prices don't make sense (

Starstreams Sep 28, 2005 2:27 AM

1 Attachment(s)
Peter Is this geometry?

I attached an image:

How are they getting 8.93mm on that horizontal line?
And how would you convert it to 1/1.8?

I don't get where the 1 comes from in the 1/1.8?
Is that the vertical dimension of the capture device in inches?

Carrots Sep 28, 2005 2:48 AM

Interesting article.

The 8.93 mm is the diagonal size of the actual sensor. Convert it to inches by typing the following in google:

"8.93mm in inches"

Then you get 0.35 inches.

Then they go on to say, that they dont quote sensor sizes using that measurement. They rather give you the size ( outer diameter)of the "casing" of the sensor. That would be the circle you see surounding the square sensor.

They also say that there is no real mathematical relationship between the two, but it appears that the square (rectangular whatever)sensor'sdiagonal is roughly two thirds of the diameter of the ourter edge of the casing.

The outer edge of the casingcircle (actually a tube, but doesnt matter for this explanation) is1/1.8"

Pull out a calculator and divide 1 by 1.8. That gives you about 0.555.

They say that the diagonal of the sensor is two thirds of thediameter of the circle.

Thus, 0.555" ( or 1/1.8") divided by three, multiplied by two should give you the diagonal of the sensor.

0.555 / 3 = 0.183

0.18 * 2 = 0.366

Which is close enough to the 0.35 inches.

To convert the actual diagonal size from scratch:

Convert 8.93 to inches = 0.35.

Multiply by 1.5 = 0.525 (as it is 2 thirds, and 1 istwo thirds of 1.5)

To convert to a fraction: 1 / 0.525 = 1.9. Put that under a 1, and you get 1/1.9"

Which is close enough considering they said ROUGHLY 2 thirds, and that we worked with 0.35 and not 0.351216576946516719.


What makes it really confusing is that the 1/1.8" is not the size of the sensor, but rather the size of the tube the sensor is in.

The 1 in 1/18" is just like the 1 in 1/2 (half). Itsone 1.8th of an inch. Or 1 divided by 1.8.

I just repeated what they said. I hope I at least made it a bit more clear.

Starstreams Sep 28, 2005 10:11 PM

Carrots wrote:

The 8.93 mm is the diagonal size of the actual sensor. Convert it to inches by typing the following in google:
"8.93mm in inches"
Then you get 0.35 inches.
But the industry doses not usually use inches right? Why would I want to convert that?

By the way.
I devided 0.555 / 3 and then multiplied by 2 as you said:
I don't know how you got 0.183?

I got 0.37

I guess what I don't get yet is why I'm deviding 1/1.8?
I need to think about this more I think.

GWHayduke Sep 29, 2005 1:09 PM

Carrots calculated 2/3 of 0.555 step-wise. His first step was to divide 0.555 by 3 (yields 0.185), then multiply 0.185 by 2 (yields 0.37). I'm not sure if anyone answered the "where did 8.93mm come from" questionyet, but the 8.93 comes from the Pythagorean theorem:hypotenuse = sqrt(A^2+B^2) where A and B are the adjacent sides of the rectangle.


Starstreams Sep 29, 2005 9:20 PM

I think I got it! :D thanks to all of you.

The difficulty is not with how you guys are explaining it; it's my deficiency in geometry and the simple terms that I should have learned in 6th grade. Anyway
Math is everything these days, can't live without it.

I wasn't clear on what the radius of a circle was so this is where I get confused buy all this.
I think I'm good now.

Again, thanks to all of you for taking the time on your replies, it is greatly appreciated. I even saved this page to my hard drive too look back on!

eric s Sep 29, 2005 9:32 PM

You have just experienced why I have been on Steves's forums for so long.
The people and the knowledge (in that order.)
The people are really nice and they know a lot, and they are great at sharing it.

I'm glad we could be helpful.


All times are GMT -5. The time now is 12:35 PM.