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Shooting on 16mm for the first time


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#21 Adrian Sierkowski

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Posted 06 March 2017 - 01:01 PM

perhaps he means


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#22 Satsuki Murashige

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Posted 06 March 2017 - 02:24 PM

Well, depth of field (or perhaps depth of focus) can be flat to the plane of focus (flatness of field), or it can have a little field curvature. In which case, you can have the center of the frame sharp, but have a gradual falloff in focus towards the edges even on a flat piece of paper.

But this a property of a specific lens design, not the camera format. This is why some old Cooke telephoto primes were called 'deep field' lenses, because they were designed for reproducing copy or for architecture, where flatness of field was important. Other Cooke lenses are famous for having a slight field curvature and thus reproducing faces with 'the Cooke look', or '3D effect.'

Not sure if this is what Tyler is talking about, but it has to do with specific lenses, not a shooting format. Now, it's probably easier to design flat field lenses for smaller formats, but it's harder to design sharper ones too. So it's a bit of a wash.

Most modern lenses other than Cooke S4s try to avoid field curvature, but then most lenses available for Super 16 are quite old. So maybe that's why the two things often get conflated? I doubt you'd have field curvature with Zeiss Ultra 16 lenses.
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#23 Tyler Purcell

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Posted 06 March 2017 - 07:38 PM

Satsuki explained my comment perfectly.
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#24 Robin R Probyn

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Posted 06 March 2017 - 10:25 PM

But this is a feature of specific lenses.. and not the format .. 16mm as you said compared to s35mm which doesnt suffer from flat depth of field.. so not really clarifying your comment ..? still confused 


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#25 Tyler Purcell

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Posted 06 March 2017 - 11:58 PM

But this is a feature of specific lenses.. and not the format .. 16mm as you said compared to s35mm which doesnt suffer from flat depth of field.. so not really clarifying your comment ..? still confused


You know exactly what I'm talking about, you're over thinking it and you're trying to poke holes in my terminology in some vain attempt to reign superiority.
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#26 Robin R Probyn

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Posted 07 March 2017 - 03:01 AM

You know exactly what I'm talking about, you're over thinking it and you're trying to poke holes in my terminology in some vain attempt to reign superiority.

 

 

Not so..I really dont.. I studied film at collage for 3 years .. and worked with 16mm film and camera,s for a good 10 years or so.. and never once heard this term.. I wonder what it means that all.. ?  its a fair question isnt it..


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#27 Simon Wyss

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Posted 07 March 2017 - 03:15 AM

I must say something on the subject of depth of field.

 

Basically, DOF is the same with all formats, equal image angles compared. In other words, if we consider “normal” focal length lenses with 65mm, 35mm, 16mm, 8mm cameras at the same geometrical iris aperture, say f/4, DOF is always of the same relative amount. With one film format everything is simply smaller than with the other but geometry does not change.

 

The decisive factor is the film, its package of layers. The overall thickness of that package doesn’t vary much from 65mm to 8mm, yet the ratio DOF-layers does. The smaller the image area the thicker a layer package stands around the image plane. Thus the smaller film formats are said to have a longer DOF, technically.

 

I haven’t spoken of the lens so far. At a given focal length we can have quite different designs. A triplet forms the image another way than a seven-elements lens does. With varifocal lenses things become still more complicated. All lenses are equal but some lenses are more equal. Needless to say that the longitudinal position of the iris diaphragm plays a role, too.

 

To play fair, we would have to adapt the grain size as well. With a 35mm camera we would be allowed to use faster films than with 16mm cameras for comparable image qualities.


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#28 Robin R Probyn

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Posted 07 March 2017 - 03:45 AM

The layers on the film itself make a difference to DoF..?..   and this is something to do with "Flat DoF" inherent in 16mm ,that s35 doesn't suffer from.. ?  


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#29 Dom Jaeger

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Posted 07 March 2017 - 08:24 AM

Basically, DOF is the same with all formats, equal image angles compared. In other words, if we consider normal focal length lenses with 65mm, 35mm, 16mm, 8mm cameras at the same geometrical iris aperture, say f/4, DOF is always of the same relative amount. With one film format everything is simply smaller than with the other but geometry does not change.
 
The decisive factor is the film...
 

  

Sorry Simon but that's just patently untrue. Larger formats require longer focal lengths to achieve the same angular field of view, and a longer focal length at the same distance from the subject will have a shallower depth of field. Are you seriously arguing that a 12.5mm lens on 8mm film will give you the same depth of field as a 100mm lens on 65mm film, given the same relative subject size and f stop?

Perhaps you're thinking of depth of focus, as in the distance in front and behind of the film plane that still allows for a sharp image to be recorded, since you mention the film layers. But this is a technician's concern, completely different from depth of field, which is what cinematographers care about.


Well, depth of field (or perhaps depth of focus) can be flat to the plane of focus (flatness of field), or it can have a little field curvature. In which case, you can have the center of the frame sharp, but have a gradual falloff in focus towards the edges even on a flat piece of paper.
But this a property of a specific lens design, not the camera format. This is why some old Cooke telephoto primes were called 'deep field' lenses, because they were designed for reproducing copy or for architecture, where flatness of field was important. Other Cooke lenses are famous for having a slight field curvature and thus reproducing faces with 'the Cooke look', or '3D effect.'
Not sure if this is what Tyler is talking about, but it has to do with specific lenses, not a shooting format. Now, it's probably easier to design flat field lenses for smaller formats, but it's harder to design sharper ones too. So it's a bit of a wash.
Most modern lenses other than Cooke S4s try to avoid field curvature, but then most lenses available for Super 16 are quite old. So maybe that's why the two things often get conflated? I doubt you'd have field curvature with Zeiss Ultra 16 lenses.



I thought it was pretty obvious that by "flat depth of field" Tyler meant that 16mm has a deeper DoF than 35mm - when everything is in focus it looks 'flat'.

But since Sat brought up field curvature, maybe I could make some observations from a lens technicians perspective.

It's very hard to pick out field curvature from an image. Even if you're shooting something flat like a chart or a wall or a supermarket shelf, there can be (and usually are) other causes for the edges being softer than the centre.

Cooke S4s don't have field curvature, even the much older Cooke Speed Panchros are very flat field lenses. I know this because when I project them onto a flat wall the corners come into focus at the same time as the centre. The corners may be less resolved, but they don't get sharper if I defocus the centre. I think one of the reasons the Panchro design was embraced by cinematographers back in the 30s was because it had a very flat field. There are various opinions on what particular lens attributes contribute to the 'Cooke look' but I don't think field curvature is one of them.

The only lenses I often see with field curvature are anamorphics, certain older zooms and some C mounts. Otherwise, even among older cine primes, it's not a prominent aberration, and among modern lenses it's basically non-existent.

In my experience Deep Field Panchros aren't any flatter in terms of field curvature than other Panchros. I'm not sure why they were called "Deep Field" to be honest, it may have been a marketing term to cash in on the deep focus trend, or to differenciate them from the more traditional telephoto design of the TelePanchros.
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#30 Robin R Probyn

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Posted 07 March 2017 - 08:37 AM

ah ok.. so thats what he means by flat DoF..   I never would that thought to call deep DoF flat..  if anything I would think it would describe a shallow (flat) DoF..   

 

I have never heard this term in all the time Ive worked in this industry... many years with 16mm .. and as a focus puller with out monitors with the white plastic Sammy,s DoF calculators.. 

 

Why not just use shallow and deep DoF.. where does flat come from..   thats a lighting term..  never heard that used to describe focus.. 


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#31 Simon Wyss

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Posted 07 March 2017 - 10:00 AM

Larger formats require longer focal lengths to achieve the same angular field of view, and a longer focal length at the same distance from the subject will have a shallower depth of field. Are you seriously arguing that a 12.5mm lens on 8mm film will give you the same depth of field as a 100mm lens on 65mm film, given the same relative subject size and f stop?

Perhaps you're thinking of depth of focus, as in the distance in front and behind of the film plane that still allows for a sharp image to be recorded, since you mention the film layers. But this is a technician's concern, completely different from depth of field, which is what cinematographers care about.

 

Fine that you are correcting me about depth of focus. Depth of field depends on a lens’ design*. Otherwise yes, I argue that a half-inch lens on 8mm film performs the same way a one-inch lens does on 16 and a 60 mm lens on full-frame 35.

 

Longer focal lengths are there with the bigger formats but as absolute values make an unsignificant difference. Computing them in would mean to subtract a handful of millimeters from the distance between film and object. It does play a role towards bigger magnification, say macro set-ups. At 1:1 the bigger format is limited downward in absolute size, i. e. objects smaller than the image area don’t fill it without longer focal lengths. One needs to switch to a smaller film size.

 

I consider the whole system, lens and film. The photographic layer package of a colour film is thicker relative to a smaller film format. The theoretical light cone of each object point projected into that thickness is of the same spacial angle with all normal focal length lenses. We should even demand similar lens designs for the comparison.

_______________________________

 

*Most prominently experienced with wide angle lenses. It makes another can of worms that one design is a true wide angle and an other a retrofocal system. True wide angle lenses are not all feasible on mirror-shutter cameras. The mirror shutter is in the way. But also with normal and tele lenses we have different concepts.


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#32 Stuart Brereton

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Posted 07 March 2017 - 10:56 AM

You know exactly what I'm talking about, you're over thinking it and you're trying to poke holes in my terminology in some vain attempt to reign superiority.

I think the fact that your comment spurred 25 other posts discussing what you meant, shows that you were a little unclear in your terminology. That's unfortunate when replying to questions from students and beginners. It just goes to show that we all need to be as precise as possible when discussing technical issues, so that we don't contribute to the mass of misinformation already out there on the web.


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#33 Satsuki Murashige

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Posted 07 March 2017 - 01:24 PM

Interesting, thanks for the correction Dom.

Are there other reasons for geometric distortions in the center of the frame relative to the edges?
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#34 Gregg MacPherson

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Posted 07 March 2017 - 03:56 PM

Satsuki,

If I read Dom correctly,  I don't know if geometric distortion is the right term...The field curvature sounds like a description of the field that is in focus. If the DOF was very small, one could visualize it as a flat plane or slighty curved surface...Otherwise,  in real life it's like a flat or slightly curved cloud.

 

But maybe geometric distortion comes with field curvature....


Edited by Gregg MacPherson, 07 March 2017 - 03:59 PM.

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#35 Dom Jaeger

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Posted 07 March 2017 - 05:45 PM

Interesting, thanks for the correction Dom.
Are there other reasons for geometric distortions in the center of the frame relative to the edges?


Well geometric distortion is a separate aberration, as in pincushion or barrel, and it's generally restricted to zooms and wide angles.

Are you referring to the video Mitch Gross did about the Cooke look where he shows the out of focus projection of a Cooke lens to have a sort of 3D bulging in the middle? That's a function of the lens design, and how the defocus flare behaves rather than actual distortion or curvature. It's a sort of illusion caused by the centre flaring evenly while the edges flare inwards. I see it in other lenses too, not just Cookes.
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#36 David Cunningham

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Posted 07 March 2017 - 08:45 PM

Yipes.

Well back to the original subject...

I personally advise using an 85 filter when shooting 500T outdoors. Yes, you can correct in post, but you will have a significantly over exposed blue layer. So, if you then further over expose you may indeed blow out those blue sky highlights. Use an 85 filter to cut the blue light getting to the film and make your post correction easier.

But if possible shoot 50D. LOL
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#37 Satsuki Murashige

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Posted 07 March 2017 - 11:53 PM

Well geometric distortion is a separate aberration, as in pincushion or barrel, and it's generally restricted to zooms and wide angles.

Are you referring to the video Mitch Gross did about the Cooke look where he shows the out of focus projection of a Cooke lens to have a sort of 3D bulging in the middle? That's a function of the lens design, and how the defocus flare behaves rather than actual distortion or curvature. It's a sort of illusion caused by the centre flaring evenly while the edges flare inwards. I see it in other lenses too, not just Cookes.


Thanks again Dom,

Very interesting. I'm sure I've seen Mitch's video, but it's been awhile. I've definitely seen that effect before as well - mostly really old lenses though.
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#38 Satsuki Murashige

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Posted 07 March 2017 - 11:55 PM

Well back to the original subject...

I personally advise using an 85 filter when shooting 500T outdoors. Yes, you can correct in post, but you will have a significantly over exposed blue layer. So, if you then further over expose you may indeed blow out those blue sky highlights.


But the OP said he specifically wanted blown-out white skies...
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#39 David Cunningham

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Posted 08 March 2017 - 12:01 PM

But the OP said he specifically wanted blown-out white skies...



True. But you'll have a hard time getting that if your skies are heavily blue due to the wrong color balance.
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#40 Satsuki Murashige

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Posted 08 March 2017 - 02:42 PM

Wouldn't the sky be yellow (red+green) if only the blue-sensitive layer on the emulsion was blown-out?

Regardless, if the red and green-sensitive layers are on the shoulder of the curve, they'll already be very desaturated. But I think I see what you're saying, ideally you want to have red+green+blue at about the same level of overexposure for a pure even white.
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