Angle of view.

awty · Apr 24, 2021

If I were to make a 6x9 camera with a 65mm lens the angle of view is 65 degrees. My 6x12 camera has a 90mm lens and this gives the same angle of view.
So my question is if I set up two poles in a field so that they were right on the edge of frame at infinity. Would the poles be still on the edge ( or there abouts) if I was using a 6x9 camera with a 65mm lens set at infinity in the same position?
Also there would be more vertical picture @6x9?
Also what is the equivalent angle of view in 35mm.
Thanks, I have a 65mm Angulan, a 6x9 roll film back and a 100 series polaroid Im planning to mate.

https://lensn2shutter.com/angleofviewchart.html

ic-racer · Apr 24, 2021

You would want to measure the actual image size on the negative made by your film gate. The lens focal length is probably best obtained from the lens datasheet, rather than trying to measure it to the sub-millimeter. For simplicity, considering the lens as a simple lens makes the math easy. You can use triangulation to figure the angle of view at infinity by placing the simple lens at the exact focal length from the film plane and triangulating 1/2 your measured film gate size.

wiltw · Apr 24, 2021

A 6x9 camera horizontally sees 1.5 * the vertical FOV , while a 6x12 camera horizontally sees 2 * vertical FOV .
But using 65mm on one vs. 90mm on the other brings inequality to the vertical AOV.

65mm on 6x9 sees about 49.5 degrees vertically, or about 92' at subject distance of 100'; about 138' horzintally
90mm on 9x12 sees about 36.9 degrees vertically or about 66.4' at subject distance of 100', about 132'8' horizontally

For vertical FOV, 65mm on 56mm frame is 1.16x frame height, so on 135 the FL would need to be 28mm. It would have similar horizontal FOV as the 6x9 camera.

Dan Fromm · Apr 24, 2021

Hmm. Which angle of view are you interested in? Horizontal or vertical? OP, I think you got the magic formula almost right.

In pidgin excel, aov = 2*degrees(atan(dimension/2)/focal length)

The vertical dimensions of nominal 6x9 and 6x12 are identical. Horizontal dimensions, 6x9 ~ 82 mm, 6x12 ~ 112 mm. 35mm still is 24 mm x 36 mm.

To answer your poorly posed question, at the same distance from your out-of-focus poles, the two cameras will see the same thing. If you focus on the poles (why on earth not?), likewise.

I gave you what you need to do the arithmetic. Do the arithmetic yourself. I'm a grumpy old man annoyed by ignorance/laziness, but don't complain about that. Instead, be proud that you provided a teachable moment.

awty · Apr 24, 2021

wiltw said:
A 6x9 camera horizontally sees 1.5 * the vertical FOV , while a 6x12 camera horizontally sees 2 * vertical FOV .
But using 65mm on one vs. 90mm on the other brings inequality to the vertical AOV.

65mm on 6x9 sees about 49.5 degrees vertically, or about 92' at subject distance of 100'; about 138' horzintally

90mm on 9x12 sees about 36.9 degrees vertically or about 66.4' at subject distance of 100', about 132'8' horizontally

For vertical FOV, 65mm on 56mm frame is 1.16x frame height, so on 135 the FL would need to be 28mm. It would have similar horizontal FOV as the 6x9 camera.

Thanks for clarifying.

awty · Apr 24, 2021

Dan Fromm said:
Hmm. Which angle of view are you interested in? Horizontal or vertical? OP, I think you got the magic formula almost right.

In pidgin excel, aov = 2*degrees(atan(dimension/2)/focal length)

The vertical dimensions of nominal 6x9 and 6x12 are identical. Horizontal dimensions, 6x9 ~ 82 mm, 6x12 ~ 112 mm. 35mm still is 24 mm x 36 mm.

To answer your poorly posed question, at the same distance from your out-of-focus poles, the two cameras will see the same thing. If you focus on the poles (why on earth not?), likewise.

I gave you what you need to do the arithmetic. Do the arithmetic yourself. I'm a grumpy old man annoyed by ignorance/laziness, but don't complain about that. Instead, be proud that you provided a teachable moment.

Strong like ox, smart like tractor.

monopix · Apr 26, 2021

You might download my AOV spreadsheet from https://www.contax139.co.uk/documentation (bottom of page). It includes 35mm equivalents.

Angle of view.

awty

ic-racer

wiltw

Dan Fromm

awty

awty

monopix

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