Why a flat chip ?

Discussion in 'Leica and Rangefinders' started by adrian bastin, Sep 29, 2006.

  1. Not such a dumb question - or is it. There would have to be a whole new range
    of lenses but wouldn't a dished senser solve the angle of incidence problem and
    allow a full 24X36 frame ?

    I had in mind the subminiature Minox with it's curved film plane.
     
  2. Because when they originally shipped the curved chips there were too many broken ones at the bottom of the bag hence the flat chips packed in a tube.
     
  3. Ye, but those last broken ones are my favourites.
     
  4. Because any existing M lens focuses at a given distance, not a range of distances. How would
    your existing M camera work if you decided to replace the flat filmback with a dished one?
    <p>
    The idea you're grasping for isn't a dished sensor. It's a flat sensor, in which the sensor pits
    are not vertical but are splayed. But that idea won't work because the angle of the pits would
    have to differ for each lens you use. A microlens above each pit seems to work...
     
  5. Eyes work pretty well. Nature didn't come up with a flat focal plane.
     
  6. They can, and do compensate for the flat digital sensor by tipping the micro-lens over the light wells that are near the edges.

    Flat is for film. There's still a good haul for digital to get all worked out on the economy of scale to make it.
     
  7. I think we need some input from an optemologist, optometrist.... someone who knows something about retinas.
     
  8. Maybe microlenses would still have a place. I can see that a long lens woulnd produce the opposite problem by needing a flatter focal plane than a wide.
     
  9. Ah eyes, well the retina is, for all intents and purposes, flat at the microscopic level of rods and cones. Even the foveal pit (the precise center of the macula at which the highest density of cones resides) is flat-ish at it's bottom. The only part of the human eye capable of seeing 20/20 (or better) is the fovea. And it's only about 1.8mm across. Even the crappiest lenses can manage to project a flat plane over such a small area. Still, it is not the eye that "sees", rather the brain compensates for any imperfections secondary to a curved receptor surface (the fundus). And, yes, the cornea is the original aspheric refractive surface.
    What does this all mean wrt photgraphy? Not much, the two systems are quite different.

    Ron (an optometrist by profession)
     
  10. The crytalline structure of silicon is not spherical. So you won't be able to get it to grow into a spherical shape. But maybe you could try amorphous silicon and place it on a spherical substrate.
     
  11. Every manufacturer of repute uses microlenses on the face of the digital sensor which compensate for the cosine effect of the angle of incidence. Considering the history and culture of Leica, the M8 will not the the exception.
     
  12. If the sensor were curved, none of the existing lenses would work on the M8. While this would make for interesting reading on these hallowed pages, it doesn't make much sense. Rectilinear lenses are designed to focus a subject plane parallel to the film in a plane at the film. A few cameras in history have been designed in this way, primarily to eliminate spherical aberation. The now retired Schmidt Cassagraine telescope at Mt. Palomar is the most famous example. This incidently permits a very wide field and low numerical aperture because the lens is so simple. Of course, Cassagraine telescopes don't have chromatic aberation.
     
  13. I think we need some input from an optemologist, optometrist.... someone who knows something about retinas.
    The eye is not a camera.
    Why a flat chip
    MY GOD! Dyxleia sucks.
    I thought this whole thread was about fat chicks.
     
  14. I posted this before. Focus on a word in a paragraph longer than five lines. Can you recognize a word more than one line or word more than one removed horizontally? Peripheral vision is built in the eye/brain combination for survival, but not for detail. The Dept. of Motor Vehicles (to get a drivers license), and a former employer (to determine if I'm fit for field work), for our Int'l members, showed I had greater than 180 degree field of vision, given my forward set of eyes in an Asian facial structure.
     
  15. The reason why chips are flat is because the processes used to put microelectronics on them have been developed to work best on flat surfaces. The masks used to selectively expose and etch the surfaces are flat so they can be laid up almost in contact with the silicon chips during processing. I suppose it'd be possible to make masks & chips that are spherical but it'd be really out the ordinary & cost cubic dollars.

    It's a little bit like the joke about why manhole covers are round - because manholes are round. AFAIK, the round shape is the only simple shape that doesn't allow a cover to fit thru itself.

    As someone pointed out, a better solution would be to modify the sensor cell well angle to better accept the photons that don't come in at right angles to the surface, but this would be difficult. Microlenses are not perfect, but by offsetting the periperal lenses they could accept more light from the center axis. Maybe the peripheral cells could be made larger to the same effect but this could lead to greater noise.

    Sigh. As an engineer I'm often unhappy with the universe and its limitations, but I try to work around them and take advantage of those weird effects that break in my favor. I'm continually surprised at how well well we've been able to crutch things and bend the rules.

    Cheers,
     
  16. Chips are flat except when they're crisps.
     
  17. Thank you all for these definitive answers - wonderful breakfast reading !

    Still, a Minox negative of a blueprint was capable of producing an accurate blueprint.

    So howabout a gently bent chip and a dedicated lens ?
     
  18. Ask youreslf if an observer at the edge of a 24x36mm frame can tell the difference in angle of a Leica ranmgefinder 15mm lens or a retrofocus Nikon F series 15mm lens
     
  19. Adrian said, "So howabout a gently bent chip and a dedicated lens ?"

    Can you imagine if the number of current lenses were doubled to accommodate a special digital sensor. Considering the bandwidth dedicated to discussing the endless permutations of the 50mm Summicron, Photo.Net would need a new server ;-)
     
  20. Kelly, if I were clinging to the edge of a curved chip I would have to crain my neck more than on a flat one. But, looking at it like that, if light waves/particles are like me they will roll into the centre and cause terrible vignetting. So, not such a good idea after all.
     
  21. If the light sensor were curved as a retina and the lenses were no longer flat field but deliberately curved field, the sensor output would have to be "flattened" just as the brain does in a way for our vision. It could never be anywhere close to a 24 x 36 frame, but a curved one, i.e. not a 2D data map.

    How would we get the sensor's input onto flat piece of paper or a flat screen?

    Or would we store our prints as curved dioramas as well and get concave computer screen with exactly one sweet spot to view our photos from? That would be neat but expensive: in material, workmanship, storage space, etc etc.
     
  22. My point with the Minox - it produces an extraordinarily flat image from a curved focal plane.
     
  23. That might more correctly be called a 'focal surface'.
     
  24. The Widelux panoramic camera has a curved film plane and a swinging lens that pans
    across it.
     
  25. A Minox image is less than 1/4" on a side. Someone is suffering from the CSI Syndrome - all you need is more magnification ;-)
     
  26. The Widelux has a cylindrically curved film plane. This is rectifiable, just as the paper wrapping on a tin can is. The poster is thinking about a much more complicated sensor surface, more like a cup than a cylinder shell and that cannot be flattened without loss, unfortunately. But so is geometry and topology. Immovable.
     
  27. "A Minox image is less than 1/4" on a side. Someone is suffering from the CSI Syndrome - all you need is more magnification ;-)"

    (Maybe) not really. The Minox has a very special lens design, using a "flattening lens" very close to the focal plane. I haven't heard of any other camera using such a lens yet. Of course the small image size of the Minox invites the designer to place an extra lens just in front of the focal plane - other cameras would need a quite large lens.
     

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