Unusual question about angle of view

[WayneF]

Just to be sure, that does meen that as long as the photograph is rectilinear, the green, red and blue line in the attached illustration of a photograph all cover the same amount of degrees, considering they are equally long?
The illustration is seen through the camera if you will, the blue line is the vertical angle of view, and the other lines are equally long.
Dont worry about the numbers, they are just made up.
View attachment 137578

Yes, a perfect regular lens should be linear in every direction, and at every location.

The meaning of rectilinear is to preserve straight lines. Fish eye lenses for example, don't.

However, some regular lenses, especially more extreme wide angle lenses, often have a little distortion, pincushion or barrel distortion, so that straight lines are curved a little, perhaps quite noticeably. Like the top line of a roof running across the top of the picture may be bowed or curved a little (at any frame edge, lines at bottom or edges too). That is not linear, and it would disrupt your measurements somewhat, however it is a different effect, still intended to be rectilinear, just failing a little.

It should not be seen in lenses that are not so wide angle.

 

[astroNikon]

One of the most commonly seen distortions is perspective convergence which is common in pictures of buildings with the use of a Wide Angle lens.

This is due to one's location in regards to the object both vertically and in distance.
This can be corrected in several ways: software, and vertical and distance to subject, or by using a tilt-shift lens.

Below is an image of a bunch of light poles. I can guarantee you they are all straight up to the eye. But the lens distorts them the further away from the horizontal plane that you get.

Thus when you mention your degrees of view, the further up you go the more they get compressed, even on a rectilinear lens. The better lens you buy, the less this will occur. You can also correct this in PostProcessing.

 

[WayneF]

That is a perspective issue, not a lens fault. More lens quality will not affect it.

Keep a lens level, aimed parallel with the level ground, and it will prevent most of that angular perspective shift that occurs when you aim the wide angle lens up. Indoors in particular, with wide angle lens in particular, keep the lens level, aimed exactly perpendicular to the walls, even if you'd rather aim them up. Otherwise, the walls will slant, same as your light poles did.

 

[Dave442]

I would suggest watching a few of the videos from Marc Levoy. He goes through some in-depth coverage of optics in photography.

Lecture 1 covers image formation and is good to watch before jumping to the optics in Lectures 3 and 4. Link to Lecture 3:


For you to consider, as in your example above, that angle of view and then the lengths are equal at different points in the image requires that you are photographing perpendicular to something like a brick wall.

 

[Bebulamar]

This might be an unusual and stupid question, and i am unsure if this is the right place to post.

In a normal photo without fisheye lense, are the angles in the photograph evenly "distributed"? (in lack of better words)

what i mean is, if the angle of view is 60 degrees (blue line), that means it is 30 degrees (red line) from the center to the right of the view.
But is it also 30 degrees from the top middle to the top right of the view (yellow line)? also does it mean that it is 15 degrees from the right to halfway to the center of the view (green line)?

Also, lets say the aspect ratio is 16/9. could you then say that its 60/ (16/9) = 33,75 degrees from top to bottom (purple line)? and could you use pythagoras ((60^2)+(33,75^2) = 68,841^2) and say that the diagonal is 68,851 degrees (pink line)?

Are these assumptions right or am i missing a big point here?

I hope someone can answer, and sorry if its a stupid question

You are only correct that if the blue line is 60 degrees then from the center to either end of the blue lines is 30 deg. However from the mid point of the blue line between the edge and center is not 15 degrees. And so the rest isn't correct.
Just to give you the result without explanation.
If the aspect ratio is 16:9
If the horizontal angle of view is 60°
Then the vertical angle of view is 32.7°
And the diagonal angle of view is 70.0°


If you can send me a message I will explain to you fully. It seems that most people here are not interested in an answer and no it's not a stupid question. For me it's an interesting question. Something I want to give answer. Not something like which camera should I buy kind of question.