Canon PowerShot S50 CCD dimensions... focal point

[cybersoya]

Hello


I own Canon PowerShot S50 still image camera and I would like to ask for help with technical properties of the camera.




I would like to use my camera for trigonometric spatial calculations, and for this I need to know some "intristic propertyes" of camera.

1-First I would like to ask what are the dimensions of CCD? Camera manual sais it is 1/1.8''.
Does this mean that on X axis it is 1 inch wide and on Y axis 1.8 inch high or is vice versa?
If X=1 inch and y=1.8 inch, than this mean that x is smaller than y, but photograps produced have all biger x than y.
Manual also sais ratio between x/y is 4/3, so does this mean that physical pixels on CCD are not actually squre where both sides are equally big, but they are rectangular with two unequal sides?





2-Manual sais focus range is 7.1-21.3 mm. If I understand correctly, when camera is focused "in infinity", than the final rear lense is 7.1mm away form CCD -focal point of the final rear lense is actually IN the CCD.
This means that focus as PROPERTY of the last final lense is at 7.1mm, the focus point as POINT where all lines intersect.
This means that when camera is FOCUSED on near objects, distance between final rear lense and CCD can be up to 21.3mm, but FOCAL POINT is allways at 7.1mm, while picture projected on CCD is FOCUSED at 7.1mm+14.2mm(=21.3), that is 14.2mm form lenses FOCAL POINT.




thank you

[stopbath]

I don't know the correct way that Canon measures the CCD but, I would suppose that the measurment is either across the sensors top, or it's diagonal (like TV measurements.)

If the measurement is across the top (which I think it is, but I may be wrong) it's simply 1/1.8 inch which is .555 inch and then down would be .4166 inch (given the aspect ratio.)

If it's the diagonal than "the sum of the square of the sides equals the square of the diagonal" will allow you to deduce the answer.

As for the focal length of the lens, those numbers reflect the focal length range of the lens. From 7.1mm in wide angle to 21.3mm in telephoto.

[cybersoya]

Hello


Thanks for all answers.

It looks like CCD sensor is 0.5555 inch wide and 0.416 inch high.


What I was trying to ask in my second question is, how can I interpret these numbers about cameras objective focal lenght, do they tell me something about WHERE the FOCAL POINT physically is on the axis going through the centre of all lenses and centre of CCD( z-axis).
To use my camera for trigonometric aplication I need to know where FOCAL POINT is in relation to CCD sensor(on z-axis), because focal point is "imaginary" center of coordiate system for triangulation, and it is a point where math geometric transformation(mirroring) is taking place, where all "similar triangles" needed for triangulation are drawn through, where all imaginary lines are drawn through.



As far as I know, EVERY single lens has its own specific FOCAL LENGHT, and when many lenses are put together they can be treated as a lens SYSTEM that has TOGETHER one single focal lenght, or can be even treated as one single lens. I imagine the specific quality of ZOOM lens sistem is that its SPECIFIC focal lenght of this lens system can be changed. But I think, once we set the zoom objective at one value and dont move it any more, than this zoom objective has its own "fixed" SPECIFIC FOCAL LENGHT as any other lens system has.

If I am able to find out the focal lenght of entire objective at given FIXED seting, then I will be able to find where the focal POINT is in relation to CCD sensor--the data I need for triangulation.



Spatial triangulation using a camera could be very easy when you could use a "pinholle camera"(camera obscura) or camera with only one lense. But when zoom objective is on the camera, than these simple trigonometric equations dont work any more, and special calibrations and complicated math corrections and modifications are needed.


I know nothing about zoom objectives nor about these math corrections, but I have read about simple method for calibration of zoom cameras, where you only need to know where focal point is.