Author Topic: focal length and field of view clarification  (Read 2906 times)

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Offline Kinga

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focal length and field of view clarification
« on: August 20, 2018, 12:28:11 pm »
Hi, I am using KeyShot to validate my algorithm - 3D pose estimation from 2D projection. I have a question about camera lens settings for perspective. In lens settings I can adjust focal length and field of view at the same time. I want to be sure if I interpret them correctly.

1) Is focal the same in both directions (horizontal and vertical)? In other words, are pixels squares?
2) The focal length is in mm. Howerver, for my task the unit must be 'pixel'. I am using following formula to calculate focal in pixels:
fin_pix = img_widthin_pix * 0.5 / tan(fovin_rad * 0.5)
I assumed that the field of view given in the settings is the 'horizontal field of view'? Is that correct? Is the vertical field of view different but not given?

Or are horizontal and vertical fields of view the same, but the focal in horizontal and vertical directions differ?

I will be grateful if someone could clarify this for me.

Kinga

Offline Kinga

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Re: focal length and field of view clarification
« Reply #1 on: August 29, 2018, 10:48:35 am »
I am afraid I asked too many unclear questions.

The question is:
How is the field of view defined? Which angle is it: horizontal - camera center and image width, vertical - camera center and image height, both ?

Offline Will Gibbons

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Re: focal length and field of view clarification
« Reply #2 on: October 05, 2018, 10:42:36 am »
I am afraid I asked too many unclear questions.

The question is:
How is the field of view defined? Which angle is it: horizontal - camera center and image width, vertical - camera center and image height, both ?

Field of view is a combination of camera distance and perspective.