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Help calculating FOV for instant camera

Started Feb 18, 2021 | Discussions thread
ProfHankD
ProfHankD Veteran Member • Posts: 9,147
Re: Help calculating FOV for instant camera

crandallwarren wrote:

Hi all,
Can anyone help me with the math on this? I have an Instax camera with a 38mm lense. The problem I’m having is that the image the lense captures is quite a bit wider than that seen through the viewfinder. This becomes a real issue when trying to isolate a certain element in a shot: say a door front, a sign etc.

I was trying to figure out a way that I could calculate the rough area of capture based on the lens length and the distance from the subject. So that, for example, if I measured a door that I want to fill the frame with, I could run some kinda calculation based on the width of the door that would tell me how far away the lens should be. Is this possible?

I’ve played around with some calculators and equations online, but haven’t gotten very far.

The image size of Instax mini film is 46x62mm. The lens is 38mm.

Much easier than that.

Take a photograph of some easy scene (e.g., brick wall) at a known distance. What you want to do is make a pair of wire frames to mount on the camera and look through for framing. Adjust the spacing between the wire frames so that when your face is up against the rear one, the view outlined by the front one matches what your photo shows. No formulas, etc.

If it were me doing this, I'd 3D-print the frame rather then bending wire. I'd use rectangular holes cut in paper to determine the spacing for the 3D-printed frame elements. Still, there's nothing wrong with bending wire....

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