So what is a "normal" lens anyway?

[Evin Grant]

There has been alot of confusion lately about what constitutes a normal lens for the Red and it's different shooting formats. So lets start with a little history. In general a normal lens is one whose focal length is the same as the format's diagonal dimention. I've modified one of Brooks FAQ examples to illustrate.

So you can see that the perfect normal lens for Red 4K is 25.5mm. By perfect I mean no wideangle or telephoto effect. By that calculation we can conclude that the normal lens for each Red format is as follows...

4.5K= 27.9mm
4K= 25.5mm
2k= 12.8mm
1080=11.9mm
& 35mm still (Film/Full Frame) is 43.3mm not 50mm as most think.

That brings up some other consideations though, it's generally believed that an 85mm lens on 35mm film is the lens of "Natural" perspective. This is because our visual cortex has the ability to narrow our preception when we concentrate on a face of person and that correspods well to the 28º angle of view of the 85mm (50mm shooting Red 4K) lens.

Here is an example of the 85mm f1.4 Nikkor on 35mm (Still) film.

Conversley if you include the periferal vision the entire FOV of the human eye is closer to 14mm in the 35mm still format (8mm in Red 4K).

Here is an example from Flickr of 14mm Nikkor on 35mm (Still) film.

This is one reason that changing lenses in mid shot (punching in) is a natural almost unnoticable edit. We do it all the time when we look at things. Of course perfect normal is not necessarily the lens we think of as normal, for almost 100 years the 50mm lens, which is ever so slightly telephoto has been the standard lens sold with 35mm still format cameras. Recently though the modern point and shoot compact has most often been fitted with either a 32,35 or 38mm lens. Slightly wide angle so this has become an increasingly more standard FOV. of course thses are all preceptions, the reason normal lenses were originally sold with cameras was thier ease of maufacture, from an engeneering prospective it's just easiest to design a good, fast lens that's the same as the diagonal of your format.

A Normal lens for Red 4K, the 25mm T1.3 Zeiss Master prime

 

[jaadgy akanni]

Nice Evin, thanks. I appreciate this kind of info. I live and learn.

 

[ZzzZZz...]

Thanks for the input Evin...
btw. can you tell me how far away you where from the camera in your lense tests? mas y menos...

I will be shooting docs, so I guess the 28-70mm nikkor is going to be the standard lense for me... you said somewhere that it had a slight focus issue while zooming. Have you seen it for yourself? Is it serious even in the heat of things, or is it "barely noticeable"? Its an IF designated lense, so I had thought it wouldn´t be a problem.

Appreciate all your tests, they helped me a lot...

 

[Milan Nikolic]

Thanks Evin this is very usefull information. We all appreciate your work.

 

[snowmotion]

That is a Great illustration & explanation

That is a Great illustration & explanation

Using 2/3" sony B4 mounts had been my Plan But it seems silly to
not use the optimal res possible If I use 35mm lenses at 2k res am I then just using the Best part of the Glass and How will framing on moniters be affected?

 

[Lenny Manfred]

do you know the conversion factor for using 2/3 lenses with the b4 mount? for example, i kept my 10mm, 20mm, and 40mm digi primes to use with the Red, would these be wide, normal and telephoto, as they are on my 2/3" camera, or would they be something else? also, i am guessing they will work on 2k only, would this be a masked 2k or the whole imager, and will this affect sensitivity and/or perspective? i have a lot of questions, i know, i am just trying to decide if it makes sense to keep these lenses for this camera.

 

[Evin Grant]

lenny, you really need 35mm optics to take advantage of Red's true potential. Sell the Digi's and buy some Ultra primes or S4s, you won't regret it.

 

[durangotang]

I disagree (in a sense).

The diagonal of the sensor should be matched to the mm of the lens to achieve the proper PERSPECTIVE. A normal lens renders the perspective that the human eye sees, not the field of view. 50mm lens have been the standard "normal" lens for 35mm since the beginning, because it is close to the diagonal of 35mm film (or a full frame sensor). The trend now is more towards 35mm and zoom lenses in the digital SLR world, but this can hardly be called "normal" in the classical since of the word.

You are correct in that a 50mm lens is actually slightly more telephoto. Of the top of my head, I think 43mm is the true diagonal and delivers the same perspective as the human eye.

In considering what a normal lens is, it is essential not to confuse field of view and perspective. Although I do find the information about the 85mm lens being normal quite interesting for face portraiture, although in reality the perspective would seem to be off to me (for example the guy in the background in your photo would not appear to be that size in real life when your eye focuses on the girl).

I think what is needed is a redesigned larger format to remedy the perspective/field of view problem.

 

[chuck colburn]

Lots of pros and some not so pro (me) have considered a 38 or 40 mm lens as standard for full frame 35 still camera formatt for many many years.

 

[Finner]

Panavision 40 is one of my favorite lenses.

 

[Charles Angus]

I have heard that the brain goes some way to "linearizing" the size of objects; that is to say, making an object look 1/2 size when 2 times farther, as opposed to 1/4 size when 2 times farther.

Then there is the fact of our very narrow field of view in the area of highest resolution. While we have almost 180° of view, we have essentially no definition at the periphery.

I did some experiments sitting at my desk.

On my Canon 20d, 50mm replicates the size my headphones on my desk appear to my eye. However, my roommate on the other side of the room looks too small at 50mm; 58mm better replicates his size. I don't think anyone is suggesting that these are "normal" lengths on a crop sensor camera; I'm not.

At approximately 10 ft. 62mm replicates the speed of an object crossing the frame, and 52mm replicates the speed of an object coming closer.

In an ordinary sized room, to replicate the field of view I feel I can see with clarity, I think I would need about a 12-14mm (my lens only goes to 28mm). This would have to be cropped at top and bottom, as I see less detail there.

I can see only about 50mm worth of detail at 10ft.
The eye works very differently from camera's. For several different scenarios, I came up with what seem to me to be several different normal lenses.

Nothing can beat experience with how different lenses will feel in different scenarios, on different size screens, on different formats.

I feel academic debate about "normal" lenses is mostly moot.

 

[durangotang]

Well said Angus.

I always try to understand the math behind something, but in essence I suppose what is real subjectively is the most important.

I would really be curious to hear others do similar experiments, and see what their results are. And if a seasoned cinematographer could chime in (which I am not), one with the Red would be awesome, I am sure my eyes would be glued to the screen.

I want to purchase a Leica M8, and am trying to decide between a 35mm Summicron f/ 2.0 and a 35mm Summilux f/ 1.4 as my primary lens. This equates to 46mm with a 1.33 multiplier, which is pretty damn close to 43mm equivalent diagonal, and should yield a "normal" perspective for most work. The thing is that the Summicron is blistering sharp from corner to corner and has better contrast. The Summilux has a more creamy look, and is very subtly less sharp in the corners (in addition to having an extra stop). I have been going over different photos on each lenses Flickr group, and the more I look the more I see the different signatures of each lens.

And it is funny that you mention it, but I have been doing experiments with my eyes and trying to see what yields the most natural result. It seems to me that if I have an object in focus, at short distance (like my hand), I do have a lot of fall off of sharpness in the corners and periphery of my vision. A LOT. Obviously more than either lens. This scenario would equate more to aperture, though. If I focus on a wall, I still have loss of sharpness (although less pronounced). Even staring off into the horizon though, there is a selective area of focus in my field of vision. I wonder what that field of view is?

I am starting to ramble now...and if I don't stop comparing images on my computer screen I may go blind (which would negate the whole point)....

 

[Prem Edpuganti]

Good discussion. My needs are for a moderate wide to moderate tele. I am planning on buying the 18-50mm Red zoom. Would this be the equivalent of 30-83mm at 4K with reference to full frame 35mm, 43mm diagonal which is what I need.

 

[Disco Legend Zeke]

The field of view is not only in the eye of the beholder, it also depends on the beholder's butt.

If its plopped into row 1, the field of view will be very wide, in row 60 it will be narrow. There is only one seat in the theatre that gives the exact angle of view as seen by the taking lens.

If a movie is destined for 4K projection on a very large screen, we might choose a lens with a wider field of view than material shot for broadcast.

On the other hand, someone with BlueRay and a home theatre will have a seat much closer to the screen than most people in a movie theatre.

 

[Jorge Díaz-Amador]

This question comes up over and over again. There is no real answer, because the eye has different "virtual" focal lengths, depending on what you are concentrating on visually. I think the eye's true focal length is about 16mm, and the area of the retina is similar to the area of a 35mm film frame (interesting coincidence).

Here is my unscientific opinion:
For S35mm (24mm wide active image plane)

The full peripheral vision of two eyes (BTW women have more) = 10mm
"Normal" wide angle view = 14-18mm
Natural field of view and perspective in normal concentration = 40-50mm
FoV when concentrating on a specific object to see detail = 75-90mm

What I have noticed is that different focal lengths have a perspective that stays the same regardless of focal length. To me the most pleasing perspective is 85mm and the most natural is 40mm. And it's true in S16mm, S35mm and even VistaVision (Leica frame still).

 

[Jason Sinclair]

For me it's about perception. The human eye can see 180 or it can see macro depending on what the mind wants to see. (Night sky looking at stars to watching an ant carry food) Walking down the street you would go wide and when you see something that catches your eye you cut in and focus on say a woman walking by. If you look at her head you will get a good 85mm, that's why I suppose everyone says that is the standard because we love looking at people both from a voyeuristic perspective but also from a subjective perspective. How many times in film are we really seeing from the protagonists POV; the person we identify with? When two people are involved intimately it's generally 85mm (in 35mm film), more so when they are talking with each other.

So it's best not to look at it from sitting at a desk but rather what it is your protaganist looking at? or what is the story element or plot line being observed. Now if you are sitting at a desk looking at words on a computer (I'm taking an educated guess that's what you are doing) then you are looking at like a 300mm, but say you sit back and reflect and see the room around you you automatically go to 15mm or so (you can even do this whilst reading). The story we are telling is about a person who is trying to work out the difference between mathamatical equations and the emotions of true experience, so he looks away from the screen and sees a collection of small cards on the wall, (24mm) and then focuses on one in particular and reads the words on it. It reads "follow the magic in your heart it is the inspiration for your life" (100mm) He then realizes that it really depends on the circumstance and continues to read the words on the page...


It's not a static view, it's a fluid experience and it is wholly dependent on the story and the percpective of the voyour (traditionaly the director) and good directors use a character of whose eyes "we" look through. Writers have done this for centuries so it's really an extension of imagination. Say for instance i say there is a woman sleeping in bed with silk sheets, you might get a shot in your mind of 25mm or there abouts and i continue the story, "she is very bueatifal" you probably go 80mm "and she has georgous brown eyes " (200mm macro) and you can imagine it all with those shots in mind while reading words on a page. Really as film makers we are replicating this experience, this universal experience caled life that combines not only reality but imagination as well. The reality we all share that includes the reality of what is and what is observable but also the emotional and subjective experience of what we do with that information. Our own individual experience and particular needs etc..


As far as wether someone watching this on a big sceen from front row or back seat or on a hdtv or on an iphone really doesn't matter because the viewer uses their perception and imagination to adapt and will see the same story. Who still can read a book and enjoy it? No lenses needed.

I think in technical arenas it's important to keep your mind on the forrest while looking through the trees...

 

[David Rasberry]

Is perspective not consistent for a given focal length? By that I mean the perceived distance relationship between viewer and object and between different objects in the field. For example, I have an old Graflex 3-1/4 x4-1/4 press camera with a 52mm Schneider Grandagon that gives a 92 degree field of view with almost no distortion and , to my eye a slightly stretched perspective. By comparison the 14mm Nikkor shot above shows a very stretched perspective and significant distortion. Stick a 2/3" sensor in the middle of that Grandagon' s field and you would only get a 12 degree FOV but the perspective should be the same. I think something in the 80mm range more closely matches natural depth perception, even though the eye covers a very wide field of view. But it is hard to equate. Wide field of view mapped to a flat image plane I guess will distort perspective compared to the eye's curved image plane.
It would be an interesting experiment to try a curved plane sensor on a camera.

 

[Andres Papousek]

This are my point of view.

If we asume that e normal lens is the one that give us the most similar viewing experiense than with naked eye then forget frame size, forget focal lengh and forget field of view.

The first change with cameras the second and third depends of perseption and "mind games" or concentration.

But we still have something that are "allways the same".

(Hope you follow me cause English is not my lenguage.)

I talking about "perspective proportion" Let me try to explain.

Im siting in a chair at a class room (in the back of it cause don study to much). In front of my theres a beatyfull brunete that don't talk to my cause im a losser. Beyond is the teacher at the front of the class room.

Now I will tell you this is a BIG class room so the image of the teacher (from head to feets) that forms in my retine has the same size of the beautifull head of the brunete in front of my.

If I take a pic with a telefoto of the head of the brunete (close up) the teacher will incrase in size and Is a take the pic of the head of the brunete with a wide angle the teacher will get small mabe the size of her pearl earring.


Between those there is the Saint grial of lenses: "the lens that sees like the naked Eye" "The Normal Lens"

What do you think about this?

This is a great forum! I'm enjoying it a lot

Andres Papousek

 

[Stefan Christou]

This was a great thread. So to resurrect it somewhat... a normal lens for Epic or Scarlet S35 will be 33.5mm right? So the 35mm RPP will be closest to that, although slightly telephoto.

Looks like durangotang may have got his wish with Epic 645:

I think what is needed is a redesigned larger format to remedy the perspective/field of view problem.

I agree, but 645 is a bit out of my budget! :head_explode:

 

[Eki Halkka]

I disagree (in a sense).

The diagonal of the sensor should be matched to the mm of the lens to achieve the proper PERSPECTIVE.

And i disagree a bit more ;-)

Perspective does not change at all when you change focal length. Only the field of view changes.

Moving camera (i.e. to match framing) is the only thing that changes perspective photography wise.

A normal lens renders the perspective that the human eye sees

...and so do all other lenses, as (this is worth repeating) a change in lens length does not change the perspective.

The same goes with field of view - any field of view can be "normal".

A shot taken with a wide angle lens, enlarged to a big print which fills your view will match what the eye sees. A shot taken with a telephoto, print out to stamp size will do the same (when watching from the same distance).

A "normal" lens shot watched on a normal size from a normal distance will also roughly match your eyes.

It all boils down to how big the final image will be, how much of your field of view it fills.