Wider Red

[Greg Lowry]

Yes it's Field Of View.

The misconception is that there is somehow a multiplier included in the given focal lenght of a lens based on the gate size. Which not true.
The focal length of a lens is not dependent on the gate size but strictly on the distance from the secondary principal point of a given lens to the imaging plane.

The FOV of the lens is dependent on both the focal lenght and the gate size. The formula for H FOV at infinity focus is 2 * arctan (Sensor width/(focal length * 2))

I have never disputed that the focal length remains the same no matter the format. in fact, you'll find dozens of posts on the old forum where I reinforced this fact.

However, the EFFECTIVE FOV (perhaps the word "effective" is necessary here for clarity) of a 14mm (35mm stills format 36x24mm) still camera lens when used on the RED ONE is not the same as a cine format purpose-built 14mm lens. I stand by my statement that the 14mm 35mm still format lens is about the equivalent of a 20mm cine lens in terms of FOV when used on the RED ONE.

Indeed, FOV is dependent on focal length and "gate size" as you call it.

Are we disagreeing or miscommunicating?

 

[Greg Lowry]

Yup. 14mm = 14mm = 14mm. You can use a crop factor to think about how the lens might look on a camera with a different size sensor, but, mm always gives the FOV of the lens.

Graeme

Yes, 14mm = 14mm = 14mm. But, for example, the RED 300 when used on the S16 format provides a FOV equivalent to between a 400mm and 500mm if recall correctly (I made the computation months ago and would have to look up the exact number). When using lenses designed for a different format it is simply not true that the "mm always gives the FOV of the lens". This is always focal length and format dependent.

A more extreme example: Does a 150mm camera lens designed to cover the 6cmx6cm medium format (e.g. Hasselblad) provide the same FOV or image magnification when mounted on a 35mm still camera? No, it doesn't.

 

[Martin Drew]

I think a lot of the confusion comes from the the talk of equivalent focal length, which sort of implies the focal length changes when a lens is used for a different format. The only big difference between a lens designed for a larger format and a lens designed for a smaller format will be that the larger format lens has to project a larger image.

Martin

 

[Martin Drew]

A cine 14mm lens is designed to cover a smaller format so it will not need to project as large an image as a still camera 14mm lens, but they will both have the same magnification. If we use both lenses on the same sized sensor the image they project will be the same. If you used a S16 14mm lens it will project the same magnification image on the sensor too but because it is designed for a smaller format it will vignette.

Martin

 

[Martin Drew]

A more extreme example: Does a 150mm camera lens designed to cover the 6cmx6cm Medium still camera format provide the same FOV or image magnification on a 35mm still camera? No, it doesn't.

It provides the same image magnification but because the sensor is smaller that image is cropped hence FOV is reduced, it is all down to the size of the sensor. If you mounted a 150mm medium format lens on a 35mm camera it would give you the same FOV as a 150mm 35mm still format lens on that same camera.

Martin

 

[Greg Lowry]

A cine 14mm lens is designed to cover a smaller format so it will not need to project as large an image as a still camera 14mm lens, but they will both have the same magnification. If we use both lenses on the same sized sensor the image they project will be the same.
Martin

This is fundamentally incorrect.

If you use both lenses on the same size sensor, the image circles for each of the lenses are obviously different -- one is larger than the other. The fact that you are cropping an image area from the large image circle effectively alters the FOV of that lens relative to the format for which it was designed.

 

[Greg Lowry]

It provides the same image magnification but because the sensor is smaller that image is cropped hence FOV is reduced, it is all down to the size of the sensor. If you mounted a 150mm medium format lens on a 35mm camera it would give you the same FOV as a 150mm 35mm still format lens on that same camera.

Martin

These are contradictory statements.

Wow. We couldn't disagree more. But rather than burn up more bandwith, I'll defer further discussion on this subject to others and will contribute further if I feel I can be useful.

It's an important discussion.

 

[Anders Holck]

Greg,
The 18 mm Zeiss Masterprime has a horisontal FOV of 68.6° in DIN S35 (24mm x 18mm)

The Nikon 18mm 2.8D Prime has a horisontal FOV of 69.2 ° on a Nikon DX DSLR (23.7 x 15.7)

Thats pretty close both in imaging format and FOV.

So a 18mm purpose built cine lens should be pretty damn close to a 18 mm still model.

 

[Anders Holck]

If you use both lenses on the same size sensor, the image circles for each of the lenses are obviously different -- one is larger than the other. The fact that you are cropping an image area from the large image circle effectively alters the FOV of that lens relative to the format for which it was designed.

The image circle has nothing to do with magnification or FOV. It only affects the net area that the lens is projecting at the sensor plane.

A 100mm lens that covers a radius of 12mm, has the exact same magnification as a100mm lens that covers a radius of 24mm.

In a 20x20mm gate size both lenses would project the same FOV. In 40x40mm the FOV would also be identical, but the first lens would vignette horrobly (project a round image)

 

[Greg Lowry]

The image circle has nothing to do with magnification or FOV. It only affects the net area that the lens is projecting at the sensor plane.

A 100mm lens that covers a radius of 12mm, has the exact same magnification as a100mm lens that covers a radius of 24mm.

In a 20x20mm gate size both lenses would project the same FOV. In 40x40mm the FOV would also be identical, but the first lens would vignette horrobly (project a round image)

You focused of an incidental part of my post.

Let me use another illustration:

A 18mm Zeiss Master Prime covering the S35 format (24.9mmx18.7mm) has a horizontal angle of view of 77 degrees.

The same 18mm Zeiss Master Prime covering the Normal 35mm format (22x16) has a horizontal angle of view of 70.2 degrees.

Unfortunately, ARRI doesn't specify the vertical angles of view and I'm not inclined to compute them myself right now, but just from these differences in horizontal angle of view one can infer that the field of view between these two formats, using exactly the same focal length lens, will be different. How could it not be?

 

[Chris Kenny]

A 18mm Zeiss Master Prime covering the S35 format (24.9mmx18.7mm) has a horizontal angle of view of 77 degrees.

The same 18mm Zeiss Master Prime covering the Normal 35mm format (22x16) has a horizontal angle of view of 70.2 degrees.

Unfortunately, ARRI doesn't specify the vertical angles of view and I'm not inclined to compute them myself right now, but just from these differences in horizontal angle of view one can infer that the field of view between these two formats, using exactly the same focal length lens, will be different. How could it not be?

FOV will be different when using lenses of the same focal length on different formats, yes. But what's under discussion here is whether FOV will be different when using two lenses of the same focal length (14mm) on the same format, just because one lens is designed to produce a larger image than the other.

It won't; it'll be exactly the same.

 

[Anders Holck]

Yes, we agree on that of course.

What I'm disagreeing with was the comments like:
"I stand by my statement that the 14mm 35mm still format lens is about the equivalent of a 20mm cine lens in terms of FOV when used on the RED ONE"
I still dont get that one

I argue that a 18mm still format lens is about the equivalent of a 18mm cine lens in terms of FOV when used on the RED ONE

or as I wrote based on specs from the two manufacturers:

The 18 mm Zeiss Masterprime has a horisontal FOV of 68.6° in DIN S35 (24mm x 18mm)

The Nikon 18mm 2.8D Prime has a horisontal FOV of 69.2 ° on a Nikon DX DSLR (23.7 x 15.7)

Almost the exact same FOV, One is a CINE lens the other is a 24x36 still model.

 

[Greg Lowry]

Yes, we agree on that of course.

What I'm disagreeing with was the comments like:
"I stand by my statement that the 14mm 35mm still format lens is about the equivalent of a 20mm cine lens in terms of FOV when used on the RED ONE"
I still dont get that one

I argue that a 18mm still format lens is about the equivalent of a 18mm cine lens in terms of FOV when used on the RED ONE

or as I wrote based on specs from the two manufacturers:

The 18 mm Zeiss Masterprime has a horisontal FOV of 68.6° in DIN S35 (24mm x 18mm)

The Nikon 18mm 2.8D Prime has a horisontal FOV of 69.2 ° on a Nikon DX DSLR (23.7 x 15.7)

Almost the exact same FOV, One is a CINE lens the other is a 24x36 still model.

The Nikon DX DLSR (23.7 x 15.7) is NOT a "24x36mm" still camera. The Nikon DX sensor is 23.7mm wide x 15.7mm high. The standard 35mm still format is 36mm wide x 24mm high. As far as I'm aware, the discussion about using Nikon lenses on the RED ONE is about use the manual F mount lenses. Those lenses are designed to cover the 36x24mm format.

I was always careful to specify that i was referring to the 36x24 still camera format, NOT a smaller APS-C sensor size such as that on the Nikon DX. Of course if the sensors sizes are about the same, the same lens focal lengths will have roughly the same FOV.

Has there been some development that will allow auto Nikon lenses to be used in manual mode? Otherwise, you'll need to use manual F mount lenses designed for the 36x24mm still format and they will not provide the same relative FOV on RED ONE.

Perhaps we can now agree on the points I made?

 

[Martin Drew]

Not contradictory at all. I presume you are talking about the maximum FOV the lens can image, I am talking about the FOV of the image taken from the sensor, that is the only significant FOV. Sure the medium format lens will have a larger maximum FOV, but we won't be using it, we will just be using the FOV defined by the area of the sensor, in this case a frame of 35mm film. It would be exactly the same size image as if we used the 150mm lens on a 6x6 camera then took the 6x6 trannie and with a scalpel cut it down to 36mm x 24mm

Any lens will have a maximum FOV beyond which it will vignette, that is defined by the magnification of the lens (determined by the focal length) and by the format the lens is designed for. That FOV, the lens maximum FOV, is only relevant in deciding whether a lens will vignette or not. If a lens is used to create an image on a sensor, assuming the lens doesn't vignette, the FOV of the sensor will be determined purely by the magnification of the lens and the size of the sensor.

Martin

 

[Anders Holck]

The Nikon 18mm 2.8D is a stll 24x36 prime with the larger image circle.
Fitting it on the red would still produce the same FOV on the RED as the 18 mm Master Prime.

What you stated earlier was that a 14mm 24x36 still lens when mounted on the RED would not be wider than a 18 mm Cine lens on the RED, which is wrong. The 14mm still lens will be as wide as a 14mm cine lens.
The 14mm 24x36 lens, when mounted on a 35mm still camera will have an even larger FOV, of cause, so would the Cine lens if the image circle was larger end the rear element would clear out from the mirror.

Greg, I will exit this discussion, as it seem to lead nowhere.
No hard feelings here, just tried to help out. Peace

 

[Greg Lowry]

Not contradictory at all. I presume you are talking about the maximum FOV the lens can image, I am talking about the FOV of the image taken from the sensor, that is the only significant FOV. Sure the medium format lens will have a larger maximum FOV, but we won't be using it, we will just be using the FOV defined by the area of the sensor, in this case a frame of 35mm film. It would be exactly the same size image as if we used the 150mm lens on a 6x6 camera then took the 6x6 trannie and with a scalpel cut it down to 36mm x 24mm

Any lens will have a maximum FOV beyond which it will vignette, that is defined by the magnification of the lens (determined by the focal length) and by the format the lens is designed for. That FOV, the lens maximum FOV, is only relevant in deciding whether a lens will vignette or not. If a lens is used to create an image on a sensor, assuming the lens doesn't vignette, the FOV of the sensor will be determined purely by the magnification of the lens and the size of the sensor.

Martin

Martin, you're a formidable opponent in a debate, with or without the facts, but I must respectfully say that you're knowledge of this subject is fuzzy. I guess we'll have to agree to disagree.

 

[Greg Lowry]

The Nikon 18mm 2.8D is a stll 24x36 prime with the larger image circle.
Fitting it on the red would still produce the same FOV on the RED as the 18 mm Master Prime.

What you stated earlier was that a 14mm 24x36 still lens when mounted on the RED would not be wider than a 18 mm Cine lens on the RED, which is wrong. The 14mm still lens will be as wide as a 14mm cine lens.
a 14mm 24x36 lens on a 35mm still camera will have an even larger FOV.

Greg, I will exit this discussion, as it seem to lead nowhere.
No hard feelings here, just tried to help out. Peace

OK, Martin. Someone else will no doubt pick up where we left off. I rarely disagree so completely with anyone on a technical matter, but in this case I do. I believe the opposite of what you say above is true. But no hard feelings indeed. It's just tech talk.

 

[Martin Drew]

OK, Martin. Someone else will no doubt pick up where we left off. I rarely disagree so completely with anyone on a technical matter, but in this case I do. I believe the opposite of what you say above is true. But no hard feelings indeed. It's just tech talk.

Just for reference that was Anders post

 

[Martin Drew]

Martin, you're a formidable opponent in a debate, with or without the facts, but I must respectfully say that you're knowledge of this subject is fuzzy. I guess we'll have to agree to disagree.

Greg

It is pleasant to have such a good humoured argument even if we do totally disagree. I am not going to give up on this one because I have the advantage of knowing I am right (don't we all). I will give a little thought to how I can convince you, I am sure there is a way. Hopefully someone who's opinion you value will chime in and you will see it.

I am sure it won't carry a huge amount of weight but I would point out that so far no one who has contributed to this topic agrees with you, of course that doesn't mean anything in itself but surely it must give you pause for thought.

Got to go to bed now, but I shall return.

Martin

 

[Greg Lowry]

Just for reference that was Anders post

Whoops, sorry!