Jump to content


Photo

Hyper-speed lenses


  • Please log in to reply
22 replies to this topic

#1 Paul Bruening

Paul Bruening

    (deceased)

  • Sustaining Members
  • 2858 posts
  • Producer
  • Oxford, Mississippi

Posted 30 August 2008 - 11:20 AM

I have been thinking about ideas from other threads:

http://www.cinematog...mp;#entry211461
http://www.cinematog...showtopic=33127
http://www.cinematog...showtopic=33034

The Barry Lyndon quote in David's post made me wonder about front element factors in lens design. As well, the distance from the rear element to the film plane. Is it correct for me to assume that a larger front element gathers more light because of its greater surface area? Is it correct for me to assume that rear element proximity effects light value, therefore a shorter distance is brighter than a longer distance (it is this way with bellows adapters on lenses. More length=less light)?

So, let's say you could use the ideas of converting a larger format, fast lens down to a smaller frame size like Techniscope and get a nearly X.5 reduction. Then you pile on the idea of using a larger front element to gather a greater amount of light. Then, pile on the idea of moving the rear element of the lens closer to the film plane (closer on a rack-over than a reflex, of course)... Assuming all those ideas could be designed into one lens and allowing for some compromise of light loss from those bigger front elements: How fast could a lens be?
  • 0

#2 Paul Bruening

Paul Bruening

    (deceased)

  • Sustaining Members
  • 2858 posts
  • Producer
  • Oxford, Mississippi

Posted 30 August 2008 - 11:34 AM

Hey Mods,

I put this in the wrong category. Would someone be so kind as to move it to "Lenses"?

Thanks,
Paul
  • 0

#3 Paul Bruening

Paul Bruening

    (deceased)

  • Sustaining Members
  • 2858 posts
  • Producer
  • Oxford, Mississippi

Posted 30 August 2008 - 11:45 AM

You know, "shutters built into the camera works" are a left-over from the pre-digital age. You could build the lens with the aperture plate on it and run the rear element almost right up to the film plane and digitally control the shutter as a built into the lens kind of thing. Arri puts the back half of the film sandwich in their mags. Why not put the front half into the lens? This would help with the tighter tolerances of FFD, as well.
  • 0

#4 Paul Bruening

Paul Bruening

    (deceased)

  • Sustaining Members
  • 2858 posts
  • Producer
  • Oxford, Mississippi

Posted 30 August 2008 - 11:57 AM

AND, if the front element being large is purposed to gathering more light, why does it need to be a biconvex thing? Why not put a thin, diopter shaped lens (concave-convex) on the front that does nothing more than gather huge amounts of light and transmit it to the normal front lens element. That would be lighter in weight. Each front element would have to be ground to match the lens and fitted with an appropriate barrel that would still be heavy. But, it would be lighter over-all than a whopping-big, biconvex, front element. Faster, as well.
  • 0

#5 Paul Bruening

Paul Bruening

    (deceased)

  • Sustaining Members
  • 2858 posts
  • Producer
  • Oxford, Mississippi

Posted 30 August 2008 - 12:50 PM

Take a moment to think of what you could accomplish with an f0.20 lens that still had a DoF of f1.2? You could shoot an entire movie of urban, night exteriors with no light set-up. You could shoot interiors with only end table lamps. AND you could do this all on slowish, high resolution film stocks.

... if only.
  • 0

#6 Paul Bruening

Paul Bruening

    (deceased)

  • Sustaining Members
  • 2858 posts
  • Producer
  • Oxford, Mississippi

Posted 30 August 2008 - 01:42 PM

Could you put a kind-of reverse LCD projector type sheet at the back of the rear element? Let's say the last surface of the element was a plano-face. A micro-thin, transparent LCD sheet could be placed between the element and the micro-flange-focal-distanced film plane to provide reflex viewing of the image. If that could be done reasonably, then that would solve the reflex mirror getting dumped (postulated in a previous post). All of these ideas put together would make a pretty complex and expensive lens. But, with a zoom this fast with all these ideas involved, you could still get all the goodies but buy fewer lenses. Or, the hell with it... sell meth and buy a whole set of primes within a week.
  • 0

#7 Paul Bruening

Paul Bruening

    (deceased)

  • Sustaining Members
  • 2858 posts
  • Producer
  • Oxford, Mississippi

Posted 30 August 2008 - 01:52 PM

I don't have a clue if there is even any kind of transparent LCD, sensor, type thingie. But, if there was, could you use it to actually accelerate, add-to or multiply light? It would be a sort-of "gain" device in the lens but for film applications.

As you might have guessed, I love film.
  • 0

#8 Paul Bruening

Paul Bruening

    (deceased)

  • Sustaining Members
  • 2858 posts
  • Producer
  • Oxford, Mississippi

Posted 30 August 2008 - 02:00 PM

I am film's bi-otch.
  • 0

#9 Paul Bruening

Paul Bruening

    (deceased)

  • Sustaining Members
  • 2858 posts
  • Producer
  • Oxford, Mississippi

Posted 30 August 2008 - 02:12 PM

An LCD senso-gain-filter could act as reflex viewer, gain device and digitally processing filter. You could spontaneously tone map the image. Let's say you are in a daylight exterior and the sun is causing a harsh 3.5 stop contrast ratio on your leading lady's face. You could dial in the amount of ND filtration on her bright side only and eliminate the need for any of those pain-in-the-ass 12K HMI fill lights. With a powerful enough CPU, you could vary the tone mapping to change the ND factor at each pixel sight and have a variation of filtration depending on the amount of light. Much of what you can do in post you could do during actually shooting. Luminance, color timing, artistic variations.

Damn. What if?
  • 0

#10 Paul Bruening

Paul Bruening

    (deceased)

  • Sustaining Members
  • 2858 posts
  • Producer
  • Oxford, Mississippi

Posted 30 August 2008 - 02:17 PM

I'll call it [i}Hypersmart Lens[/i]. It could gain the dark sides and filter the bright sides. If you were shooting a night exterior with a single point of light. You could bring down the high contrast by brightening the dark side and darkening the bright side.
  • 0

#11 Glen Alexander

Glen Alexander
  • Guests

Posted 26 October 2008 - 01:12 PM

AND, if the front element being large is purposed to gathering more light, why does it need to be a biconvex thing? Why not put a thin, diopter shaped lens (concave-convex) on the front that does nothing more than gather huge amounts of light and transmit it to the normal front lens element. That would be lighter in weight. Each front element would have to be ground to match the lens and fitted with an appropriate barrel that would still be heavy. But, it would be lighter over-all than a whopping-big, biconvex, front element. Faster, as well.


Pick up and read Borne and Wolf, or at least the lens maker equation.

If you put a big massive lens up front, say 8.5", most are designed to have a focal length around 1000mm. You need an initial lens with a massive curvature to get down to something like 50mm, without have a telescope for a lens. massive curvature tends to separate the wavelengths of light so that don't focus at the same point/region. Massive curvature is also a lot harder to maintain tolerance over the surface.

Go ahead and get a celestron 10" or 14" lens and try to build a 50mm F0.2.
  • 0

#12 georg lamshöft

georg lamshöft
  • Basic Members
  • PipPipPipPip
  • 310 posts
  • Berlin

Posted 19 November 2008 - 10:39 AM

The physical f-stop limit is f0.5, which is one stop faster than the famous planar used by Kubrick.
  • 0

#13 Simon Wyss

Simon Wyss
  • Basic Members
  • PipPipPipPip
  • 1414 posts
  • Other
  • Basel, Switzerland

Posted 19 November 2008 - 03:42 PM

The physical f-stop limit is f0.5, which is one stop faster than the famous planar used by Kubrick.

The theoretical limit is f 0.5, in practice one ends at f 0.53 where the light is just grazing the front element. F 0.7 is already very tricky to compute. An alternative is the mirror lens.
  • 0

#14 Glen Alexander

Glen Alexander
  • Guests

Posted 19 November 2008 - 05:51 PM

The theoretical limit is f 0.5, in practice one ends at f 0.53 where the light is just grazing the front element. F 0.7 is already very tricky to compute. An alternative is the mirror lens.


Yes, i looked at designing a curved mirror but the manufacture said they couldn't maintain tolerance over the curvature and didn't want to quote. .5 limit is only for 'simple' convex or concave lens. with a parabolic lens, it is possible.

Edited by Glen Alexander, 19 November 2008 - 05:54 PM.

  • 0

#15 Simon Wyss

Simon Wyss
  • Basic Members
  • PipPipPipPip
  • 1414 posts
  • Other
  • Basel, Switzerland

Posted 21 November 2008 - 11:02 AM

Never despair! There is Mr. Kouchatchki a few kilometers from where I live who has ground and polished his own concave mirror from pure aluminium. He says it is better than glass. Now he observes the stars with the best reflector on earth. In case of interest I can provide you with the address.
  • 0

#16 Paul Bruening

Paul Bruening

    (deceased)

  • Sustaining Members
  • 2858 posts
  • Producer
  • Oxford, Mississippi

Posted 21 November 2008 - 11:39 AM

Never despair! There is Mr. Kouchatchki a few kilometers from where I live who has ground and polished his own concave mirror from pure aluminium. He says it is better than glass. Now he observes the stars with the best reflector on earth. In case of interest I can provide you with the address.


Can he grind glass elements?
  • 0

#17 Simon Wyss

Simon Wyss
  • Basic Members
  • PipPipPipPip
  • 1414 posts
  • Other
  • Basel, Switzerland

Posted 22 November 2008 - 06:42 AM

I'd have to ask him. How much time will you give me ?
  • 0

#18 Glen Alexander

Glen Alexander
  • Guests

Posted 22 November 2008 - 12:02 PM

These are the people I contacted about my design

http://www.jmloptical.com/

They are willing to do one offs for a reasonable price if they can meet your specs.
  • 0

#19 Glen Alexander

Glen Alexander
  • Guests

Posted 22 November 2008 - 12:15 PM

Never despair! There is Mr. Kouchatchki a few kilometers from where I live who has ground and polished his own concave mirror from pure aluminium. He says it is better than glass. Now he observes the stars with the best reflector on earth. In case of interest I can provide you with the address.


how can he guarantee surface smoothness? what are his tolerances? what does he use for such precise measurements? does he have a flatbench? how does he quanitify comatic aberrations?

i would be somewhat hesitant, aluminum doesn't have a crystalline structure and there is NO such thing as "pure" aluminium, there are always grades, 6061, 5051, 5356, medical grade, etc,.....

there are methods to reduce the surface roughness but one guy by hand seems like it would take a long, long time. why doesn't he put a silver finish on his mirror?
  • 0

#20 Simon Wyss

Simon Wyss
  • Basic Members
  • PipPipPipPip
  • 1414 posts
  • Other
  • Basel, Switzerland

Posted 22 November 2008 - 01:30 PM

Man, you're eating me up with your questions.

He is a hobby astronomer and sole hand worker, has no instruments, trial and error until he reaches the result. On the JML flash intro I read High Speed Manufacturing. There you are: either a solitaire which takes time or a company eager to set up series.

I cannot cope with your interest in entering manufacture details. Seems to me that you have to know the adventure for yourself. Most certainly you can find an optical specialist in your country. If you'd insist I should politely ask you for the dimensions before we discuss surface roughness.

So long
  • 0


Ritter Battery

Wooden Camera

Media Blackout - Custom Cables and AKS

CineTape

Tai Audio

Glidecam

Willys Widgets

Opal

Visual Products

Broadcast Solutions Inc

FJS International, LLC

Metropolis Post

Rig Wheels Passport

Abel Cine

rebotnix Technologies

Gamma Ray Digital Inc

Technodolly

CineLab

The Slider

Aerial Filmworks

Paralinx LLC

Visual Products

Abel Cine

Media Blackout - Custom Cables and AKS

rebotnix Technologies

CineLab

Technodolly

Ritter Battery

Aerial Filmworks

The Slider

Broadcast Solutions Inc

Willys Widgets

Gamma Ray Digital Inc

Tai Audio

Paralinx LLC

Rig Wheels Passport

FJS International, LLC

Metropolis Post

Glidecam

Wooden Camera

CineTape

Opal