Large format angle of view

[Eric Coughlin]

I don't know if I'm getting my terms right here...my question is, okay, so, say you have a 50mm lens on a Super35 sensor, and that gives you the same framing as say a 100mm lens on an Alexa 65 sensor.

Now, I know with a 100mm lens on a Super35 sensor compared to a 50mm lens on a Super35 sensor with the same framing, that you're now seeing less of the background, not in terms of depth of field (as you can just stop down to get the same depth of field), but in terms of angle of view, I believe is the term.

Okay. So does that mean that on an Alexa65 sized sensor, you're always seeing less of the background because your angle of view is narrower to achieve the same framing?

And now if we exaggerate this and imagine a massive sensor, say 10 times the size of Super35, that now needs a 500mm lens to get the same framing, are all the images from that going to have a super compressed background making it practically impossible to ever see much of the background, even with what is wide framing?


And the follow up question, what angle of view in relation to sensor size most closely matches human eyesight?

 

[Mitch Gross]

You may find this video I made almost a decade ago useful. Toward the end I demonstrate what I believe you are asking.

In short, angle of view remains the same while apparent depth of field does not.

https://www.abelcine.com/articles/blog-and-knowledge/tutorials-and-guides/a-lens-is-a-lens-is-a-lens

 

[jcs]

The concept of Equivalence should make it clear regarding FOV and depth of field, regardless of sensor size: https://brightland.com/w/the-full-frame-look-is-a-myth-heres-how-to-prove-it-for-yourself/

Using a crop factor relative to a 35mm FF sensor (originated in the stills world), you can use simple math to compute equivalence for any two sensors.

You can use a DOF simulator to check FOV and DOF interactively: https://dofsimulator.net/en/

 

[Samuel H]

If you don't move the camera and the lens provides the same angle of view, and you also adjust aperture so that DoF doesn't change, then the image is exactly the same... in theory, because the character of the lens, the resolution of the sensor, etc, will introduce some differences. And you probably won't compensate focal length and aperture exactly either.

The part where you "don't move the camera" is actually the most important one: many people do comparisons in which they move the camera to compensate for the different angle of view of the lens, and this screws the equivalence. But if you're comparing a 50mm on S35 to a 100mm in a sensor that's exactly twice as wide, with the camera always in the same spot, and you close your aperture by two stops to keep DoF constant, the image should be identical.

 

[Eric Coughlin]

If it's not focal length, then what determines angle of view?

 

[morgan_moore]

focal length AND sensor size.

35 is wide on a 645 sensor.

10.8 plate cameras may have a 300mm lens to give a 'normal' FOV.

70 is a decent telephoto on 2/3

 

[Mitch Gross]

Focal length indicates how much magnification is occurring within the lens. But a lens has no idea what is behind it so it doesn't know how much of the projected cone of light will be used. Think of a sensor as a small rectangular window. Light is projected out the back of a lens and the size of the window dictates how large a field of view is captured. A bigger window captures a bigger field of view.

 

[Run&Gun]

...what determines angle of view?

focal length AND sensor size.

This

 

[Eric Coughlin]

Focal length indicates how much magnification is occurring within the lens. But a lens has no idea what is behind it so it doesn't know how much of the projected cone of light will be used. Think of a sensor as a small rectangular window. Light is projected out the back of a lens and the size of the window dictates how large a field of view is captured. A bigger window captures a bigger field of view.

But field of view is different than angle of view.

 

[jcs]

It’s really pretty simple:

 

[Run&Gun]

The terms Angle of View and Field of View are used interchangeably, even though there are technical differences in the definitions. Angle of View is generally describing the actual angle of view(i.e: 90 degrees), whereas the Field of View could be described as the linear view in front of the camera/lens(which can/will change depending on the angle of view of the camera/lens system and how close/far away it is). I'd say for most of us, in practical terms, we understand what is generally meant when someone uses either one.

https://shuttermuse.com/angle-of-view-vs-field-of-view-fov-aov/

https://en.wikipedia.org/wiki/Angle_of_view

EDIT: Just saw JCS posted that image from one of the linked articles while I was posting the above.

 

[AndreeOnline]

Okay. So does that mean that…

As has been established, there are no inherent sensor/format looks per se. There is a lot of overlap between formats even if we're only take actual, existing lenses into account. In a theoretical scenario like a 3D or VFX software where you control sensor size and lenses—you can match anything.

And the follow up question, what angle of view in relation to sensor size most closely matches human eyesight?

If we start at the wrong end and imagine a portrait taken with a 14mm lens on a full frame camera 1 feet from someone's face: we know that is not how people look—even if we get up close. It's the wrong geometrical perspective.

It might be up for debate, and I'm not sure I've seen a single focal length be said to rule them all, but there's a general consensus that around 40mm on full frame looks natural. I've got nothing against ballparking it to 35-50mm, in the spirit of using common focal lengths. For other sensor sizes use any converter of the many available. That takes care of the perspective part, but the thing is that if you count peripheral vision the human eye sees about 140 degrees horizontally. And what's that? Around 7mm on full frame.

So there is no lens that is as wide as our vision that has the same perspective. Granted: we don't really "see" in 140 degrees angle of view. Even if we benefit from the outer edge of our vision for orientation, I'm sure we can agree that our cone of focus is much smaller than that.

 

[morgan_moore]

And the follow up question, what angle of view in relation to sensor size most closely matches human eyesight?

Im struggling to answer this!

50mm always?

But S35 35 looks like FF50?

What I do know is that camera to subject distance is the most critical creator (optically) of mood.. eg love scene shoot from as close as a lover (S35 20?).. spy scene? shoot from way back like a spy (s35 200?)

 

[Greg_E]

There are two viewing angles for human vision, perception and concentration. Perception has been said to be around a 28mm FF lens, and concentration to be around a 135mm FF. In this case, full frame is the 36x24mm film frame. This info is from memory from old photography books long since lost in a house fire, or I'd scan the page for everyone. I don't Remember the actual angles, but you can probably find a chart based on those two lenses and frame size.

 

[Mitch Gross]

"What angle of view in relation to sensor size most closely matches human eyesight?"

Its entirely culturally dependent. There are some cultures where people get very physically close to one another when speaking. There are other cultures where they stay at a greater, more reserved distance. If I am concentrating on your face from three feet away compared to seven feet away, then my perception of what lens angle of view matches my vision is quite different.

There is no such thing as a "normal" lens.

 

[morgan_moore]

I think the concept of a normal lens is where looking in the viewfinder is no different from looking through a hole in a bit of cardboard

But your cardboard Evf can have holes of infinite sizes.

It really only works with optical finders that don’t shrink/magnify

One gets that with a ff film Dslr and 50 - hence the rep of 50 as normal

 

[combatentropy]

you're now seeing less of the background, not in terms of depth of field [...] but in terms of angle of view

The thing you're thinking of, compression, is mainly a factor of distance from the camera to the subject. Forget your camera for now. Throw it in the trash (metaphorically speaking). Walk around with your own naked eye.

Do you see that person in the distance? Now see the bus behind them? Oh how it looks so close to them! That thing where a long lens compresses depth, and makes it look like the bus is right behind the person, is simply a matter of distance.

Telephoto lenses are associated with compressed depth. That is because they crop a lot. So everything that fits in the frame has to be far away. And things that are far away look close to things behind them.

---

Walk around. Walk right up to someone. Put your face in their face (I hope you know this person.) Look how big their nose is! Again this is a factor of distance. It is not a factor of what lens you used (because you are still using your fixed-focal-length eyes.)

Big noses. Compressed backgrounds. These are factors of distance, from you to the subject. They have nothing to do with lenses. Lenses just crop.

 

[combatentropy]

what angle of view in relation to sensor size most closely matches human eyesight?

The following is original to me (as far as I know) and I will not be offended if you cast all manner of doubt upon it.

So there are two ways to answer this question.

1. Literally. What is the angle of view of your eyesight? Well, obviously it is quite wide. What lens would it take to capture all that you're seeing right now? Would it be something like a 14mm lens on a full-frame camera?

But then you have a problem. The camera has captured all that you see with your eyes, from left to right, but it looks warped. This is not just a wide angle, it is a fish-eye!

2. Geometrically. I think that the reason a 50mm on a full-frame camera looks "normal" has nothing to do with its field of view. I will repeat. I think that the reason a 50mm on a full-frame camera looks "normal" has nothing to do with its field of view.

Let us grant that 50mm on a full-frame camera looks normal. Why?

Well, I was calculating the other day. Do you know the formula for calculating the angle of view of a lens? Wikipedia knows, and it is not a friendly formula. It involves a trigonometric function called arctangent. It's not easy to do in your head. It's not even easy to do on a calculator. That's why I made my own web page to do it.

It's a funny thing about a 50mm lens on a full-frame sensor. Its diagonal angle of view is almost exactly 45 degrees. 45 degrees is one half of a right angle.

Do you know what else has right angles? A picture frame.

I cannot fully connect the dots, but I think that a 50mm lens's rightness has something to do with right angles and nothing to do at all with the human eye's field of view.

Just a theory.

 

[jcs]

The 'normal' human vision matching lens has been studied in depth. 50mm as 'normal' was chosen by the creator of Leica cameras. 50mm +/- works for representing normal human vision for full frame cameras (e.g. 40-60mm can work). With a Super35 crop of 1.5 that's 27-40mm (where 50mm on FF becomes 33mm on S35 (typically 35mm is used (primes))). You can use crop factor math to compute normal lenses for any sensor size. See the example tables here: https://en.wikipedia.org/wiki/Normal_lens (see also Cinema section based on projection and typical viewing distance).

 

[jcs]

For the Alexa 65 a normal lens would be (using full image circle of sensors): sqrt(36^2 + 24^2)/sqrt(54.12^2 + 25.58^2) = .72 (crop factor), 50mm/.72 = ~70mm.