Results 1 to 5 of 5

Thread: how to tilt-shift DSLR lenses and video projector lens shift work?

  1. #1
    Join Date
    Jan 2018
    Posts
    14

    Default how to tilt-shift DSLR lenses and video projector lens shift work?

    I ask this question because I'm working on a project and fear reinventing the wheel or making an inferior method of something that can be done easier and the knowledge publicly available.

    This is my setup:
    https://i.imgur.com/6iwGXOl.jpg

    Center of the lens on the right side does some pincushion distortion before the beam reaches the other lens. I need to be able to change where the center of distortion over time mechanically.
    Right now I plan to use stepper motors.

    But I think there are similar methods although used for a different purpose in both the photography world and video projector world.
    For photography there are tilt-shift lenses.
    For video projectors there is lens shift.
    With lens shift I get perfect, undistorted video projected up to 100% above, below, left or right from center of the lens.

    How are both of these done? Is it similar to my current setup, or use something else such as tilting fresnel lenses?
    Should I stick with my current setup for offsetting the center of distortion or are there better ideas?

    I apologise in advance for poor topic title. Was originally "how do tilt-shift DSLR lenses and video projector lens shift work? And am I trying to reivnet the wheel?" but didn't fit character limit.

  2. #2
    Join Date
    Jun 2009
    Location
    St. Louis, MO
    Posts
    648

    Default

    High end video projectors can translate the image plane as you showed in your diagram, but some also allow adjustment of "Scheimpflug" or the plane of sharp focus. This is done by tilting the lens in X/Y.
    "There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso

  3. #3
    Join Date
    Oct 2012
    Location
    Germany
    Posts
    1,029

    Default

    ... I have a dental-scanner with vertical laser line and two "Scheimpflug" cameras, what is used to 3D-scan rotated objects (and some more cameras salvaged from others of this type scanners).

    With the Scheimpflug-setup the vertical central plane is more in the focal area, than with a conventional stereo setup ...

    Viktor

  4. #4
    Join Date
    Jan 2018
    Posts
    14

    Default

    I'll admit I've never had chance to look inside either tilt shift camera lenses or video projection lenses with lens shift feature. Both are too expensive for me to attempt to disassemble. Nor have I had luck finding info on someone else doing it or explaining what's inside.
    My only guess has been that either all some lens elements are physically shifted along the DMD or LCD but I haven't been able to understand how that won't cause distortion as center of lens changes for other lenses and DMD/LCD.
    The only place I've found any info on this has been a youtube video for a DIY video projector where someone used a (fresnel) lens tilting, not shifting.
    https://youtu.be/Rp8HIf5eUpo?t=4m45s
    The projector in that video is the only one I've seen where someone attempts to use fresnel lens tilting to do keystone correction optically rather than in software.
    I guess at extreme projector to screen angle lens tilting could also help with uniform focusing, but I haven't seen it implemented as such a feature in one.
    Maybe the reason for both of the above is introducing chromatic aberration?
    Last edited by widaxi; 02-06-2018 at 10:03.

  5. #5
    Join Date
    Jan 2019
    Posts
    1

    Default DSLR lenses

    I was also not known to this and I got the chance to know about that. I just bought a DSLR camera and I was thinking about how to shift the DSLR lenses and the video projectors. Now I can also do that.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •