To quote myself later in the post:

"What I am after is a method for determining an accurate measure of a captured angle of view (with the Apertus 1/2.5" chip) Considering that different lenses are designed for different sized sensors (ie. different sized image circles)."----------------------------------------------------------------------

Okay, So what I have gathered is that

"A Focal length is A Focal length!"

The Field Of View, not the focal length,

will change depending on the

format of the camera

http://www.rmassa.com/specsheets/Basics_of_Lenses.pdfSo using a lens on a smaller chip will produce an image with narrower FOV...

I understood that all along!

What continues to elude me is when working out the AOV for a captured image, when do image circles come into play?

Lets see if I have got this part right...

Lenses have larger / smaller image circles; Depending on what size sensor they have been designed for. For example, take three 10mm lenses: although the image circle changes in size, the angle of view remains the same?

(see below) Now if the above is correct, the size of the image circle (as well as the size of the chip) affect the total captured angle of view!?

If we use a 10mm lens designed for 1/2" sensors, we are going to get a wider AOV than if we use a 10mm lens designed for a 1" sensor.

(see below)----------------------------------------------------------------------

What I am after is a way of determining the

Captured Angle of View when using lenses with the Apertus Camera.

I have found a formula which will easily calculate the AOV- given the focal length of the lens and the size of the sensor.

But this formula does not consider the size of the image circle!

My presumption is that the above formula assumes that the image circle is the exact correct size for the sensor!? (Im not sure)

What I am after is a method for determining an accurate measure of a captured angle of view Considering that different lenses have different sized image circles.(Please bear with me... I think I am close to understanding this dilemma of mine, I hope I have articulated my issue well enough that someone can help!)

Additional notes:

(just a place for me to dump my notes on this)

Example lens

Imager Size 1/2" (5.76 x 4.29)

Focal Length 6mm

Horizontal Angle of View 56.93°

Apertus sensor size: 5.70 x 4.28

----------------------------------------------------------------------------------

Require 2 formulas

1: Calculate captured angle of view for 1/2.5" Apertus chip (5.70 x 4.28)

2: Calculate theoretical Focal Length if 1/2.5" chip was scaled up to 1/2" size.