Field of view, field of angle, and determining height

[ThirtyWest]

Hi folks,

Trying to understand the concept here so bare with me:

Looking at the mavic air 2 I see it shows a field of view of 84 degrees on its 1/2" CMOS.
As I understand it, that FOV of 84 degrees is measured diagonally across the CMOS much in the way we measure TVs and monitors. A post somewhere online said they were done that way. I can't find the URL to post it here.

1. What is the size/shape of the CMOS?

2. Does the native resolution (which I believe is 4:3 on the MA2) mean the actual CMOS is built at a 1.33 ratio (length to width)?

I'm asking to come up with the trig needed to determine the height I'll need to fit large subjects in the frame when shooting straight downward.

I practiced on a football field (300 ft wide) and it was about 65 meters to get goal line to goal line in the frame--a little less actually. It was shot in 4:3 and fit about 225 ft. across the field as expected.


I've got no trouble doing the math, but I need to know the true angle to start crunching.

Also, why do they call it field of vision when it seems like field of angle is more appropriate.

thanks to anyone stepping up to dumb it down.

 

[brett8883]

Hi folks,

Trying to understand the concept here so bare with me:

Looking at the mavic air 2 I see it shows a field of view of 84 degrees on its 1/2" CMOS.
As I understand it, that FOV of 84 degrees is measured diagonally across the CMOS much in the way we measure TVs and monitors. A post somewhere online said they were done that way. I can't find the URL to post it here.

1. What is the size/shape of the CMOS?

2. Does the native resolution (which I believe is 4:3 on the MA2) mean the actual CMOS is built at a 1.33 ratio (length to width)?

I'm asking to come up with the trig needed to determine the height I'll need to fit large subjects in the frame when shooting straight downward.

I practiced on a football field (300 ft wide) and it was about 65 meters to get goal line to goal line in the frame--a little less actually. It was shot in 4:3 and fit about 225 ft. across the field as expected.


I've got no trouble doing the math, but I need to know the true angle to start crunching.

Also, why do they call it field of vision when it seems like field of angle is more appropriate.

thanks to anyone stepping up to dumb it down.

We don’t have official dimensions of the sensor buts is probably about 6.4mm x 4.8mm. It’s a rectangle.

Yes 1.33:1 aspect ratio. 4/3

FOV is probably measured diagonally in this case yes. It’s called Field of view because that’s the viewing angle. It’s what the sensor can see. It’s determined by both the focal length of the lens and the sensor dimensions. I wouldn’t take the 84 degrees to be scientifically accurate. Just an approximation.

 

[Deleted member 103366]

Bear in mind that the indicated height is not necessarily spot on, is it not simpler to fly over the object and climb and yaw until you have a satisfactory view?

 

[JC in New Hampshire]

Getting it right might also allow for measuring large objects through analysis of an image taken at a known altitude.

 

[Mark_Y]

Calculating the True Field-of-View: e.g., it's 74.5° on Mavic Air video, not the advertised 85° !

Summary: It's very likely that when you plan and then simulate a drone mission, you aren't setting the correct field-of-view (FoV) for the simulation. This leads to situations where you don't get quite the result you'd hoped for. This post gives an example of how to find the correct number to...

mavicpilots.com

You may find this helpful.

 

[Gregdd]

OK I just made a post that might answer your question just as your post answered my question. FOV is calculate diagonally which I did not know but you might use my post to calculate the height you will need. Although this post is OLD now so you probably already figured it out.

Mavic 2 Pro actual FOV

I made some measurements to check my actual FOV of the M2P. The measurements were in Camera mode. At 200cm from the wall the width of the image was 248cm. By my calculations that is only 64 degrees not the advertised 77. I checked this at different distances just to corroborate my...

mavicpilots.com

 

[FLDave]

I thought camera lens field of view referred to the angle from the lens to a horizontal line, not diagonal. So draw your straight line from the lens to the distant point. To the left will be half the field of view angle and to the right the other half. This will give you a right angle triangle of which you know the angle, the adjacent leg and the opposite leg. You can now calculate the length of the opposite leg which is half of the field of view width.
The vertical field of view angle will be smaller than the horizontal field of view since the picture is not square.

 

[Gregdd]

I thought camera lens field of view referred to the angle from the lens to a horizontal line, not diagonal. So draw your straight line from the lens to the distant point. To the left will be half the field of view angle and to the right the other half. This will give you a right angle triangle of which you know the angle, the adjacent leg and the opposite leg. You can now calculate the length of the opposite leg which is half of the field of view width.
The vertical field of view angle will be smaller than the horizontal field of view since the picture is not square.

It would appear that any listed FOVs are diagonal. Did you look at the link I posted above? It shows the math. The math I did clearly shows that the DJI posted FOV does not match my numbers so would make sense now that the numbers are diagonal.

 

[Meta4]

I thought camera lens field of view referred to the angle from the lens to a horizontal line, not diagonal

Camera makers always give the lens viewing angles as the diagonal angle.

 

[FLDave]

A little clarification, since the lens field of view would be a circle the field of view of the lens would be a diameter of that circle. So, for a rectangle picture to fit within this circular field of view the picture diagonal becomes the diameter of the field of view circle for the lens,