Originally Posted by hellosailor
"FoV and apparent FoV are angular measurements and FoV at 1000 meters is a distance."
Those are two different ways to say the same thing. The angular measurement will always translate into the same FOV at the same distance, 1000 yards or otherwise.
Anyone who would try to convince you otherwise, is either a charlatan or failed high school geometry. Included angle, distance, all basic fixed numbers and this is how we get cosines and tangents and all those other painful numbers that used to come from a book of tables before pocket calculators replaced slide rules. A 3-4-5 triangle will always be a 30-60-90 degree triangle. Same same.
And whether it is the field stop or the exit pupil, as long as the image is being cropped the same way at the same point, those will be the same as well, all else being equal.
Wow. Wouldn't ever try to convince you otherwise. Wouldn't want to be thought a charlatan. And I can't even remember high school geometry.
But you may want to check your tables or slide rule. A 3-4-5 triangle is a 37-ish/53-ish/90 triangle.
And the relationship between FoV and apparent FoV is determined by the following:
tan ω' = Γ x tan ω
Apparent field of view:2ω'
Real field of view:2ω
The differing ways of saying the same thing are important to the consumer because they are the way products are labeled. If you understand the differences you can compare the products properly...if you have your slide rule with you when you are shopping.