CCD size affecting viewing size

[Thomas 0]

How major a factor does CCD size make in the field of view. I've been studing the basic equations and it looks like this.

 

1/3" CCD, Object 200 meters away, 50 meters of width of view=

 

F= (4.8 x 20000)/5000 (All in mm)

F= 19.2

 

2/3" CCD, same

 

F= (16.93 x 20000)/5000

F= 67.72

 

So I need a much bigger lens to get the same width of view, or am I just not doing my math correctly?

[Cooperman 0]

Hi Thomas,

 

Maths was never my strong point, but your focal length figure for the 1/3" example looks pretty near spot on.

 

2/3" er, not quite.

 

50metres width coverage at 200 metres distance should be

approx. 18mm for 1/3",

and 35mm for 2/3".

 

The answer to your question is simply that imager size is always going to be a crucial factor when considering the field of view.

 

But it's perhaps better to look at the problem from the other direction.

If you standardise on a format for most work, for arguments sake 1/3", then you have a vast array of optics available, which will cover most projects (obviously assuming the camera has an interchangeable lens mount!).

 

To maintain the same width coverage (field of view), as the imager gets larger, so the focal length must become longer.

 

25mm on 1" is the same as 12.5mm on 1/2",

16mm on 2/3" is the equivalent of 8mm on 1/3" (they are all 'standard' lenses).

[Thomas 0]

Errr...found my math error. Corrected it and my numbers. Just remeber kids, when you double one number but end up with a result four times as big, then maybe you made a goof.

[Cooperman 0]

That's probably why I never made any money out of my installs, all those years ago