how to find lens centre on the sensor ? calling all geometry nerds

[Daniel Crooks]

hi people

I'm working on a project shooting railway lines and i need to place to the camera (epic) dead centre of the tracks and pointing perfectly parallel towards the vanishing point. I've been doing a number of bench tests using known straight parallel edges and the aligning with centre target of the guide frame overlay but getting some very erroneous results. The conclusion I've come to is that 'principle centre' or optic or geometric centre of the lens does not in fact line up with the pixel centre of the frame ( which i suppose is to be expected). So... does anybody know a simple(ish) method of determining where on the sensor (i.e. a pixel co-ordinate) the actual optical centre of the lens is ?
There's a few white papers online but they involve some serious maths and/or lab based laser equipment. I'm really hoping someone has something a little more practical for the non optics engineer.

cheers../Daniel

 

[Lauri Kettunen]

Display a grid on your computer display. Then point your camera towards the grid and move your camera along a straight line towards the display without rotating the camera. There is exactly one pixel which points all the time to the same point of the display while you move the camera. That's the optical centre point on the sensor you are looking for.

 

[Todd T]

Keep in mind that moving parts of the lens (Focus, Zoom) as well as external filters will cause the image to slightly shift .