Site Sponsors
Results 1 to 7 of 7

Thread: Macro Lens Question (entrance pupil)

  1. #1
    Shelby Lewis
    Guest

    Macro Lens Question (entrance pupil)

    This isn't MF specific, but I bet I'll end up using an MF lens... so I thought I'd pose it here... and you guys all know your lenses

    I have an idea for a shot that I'm wanting to do that uses stacked exposures.

    The catch... it stacks from macro to infinity. In order to pull this off, you need a lens where the entrance pupil doesn't move. This is usually done with a bellows in conjunction with focusing via camera-body-movement (for/aft)... which means a custom setup. The lens doesn't move at all. But there are a few lens, mostly on compact cameras, where the entrance pupil doesn't change as you focus. I'm wondering if the internal focusing slr lenses are included in this group...

    Does anyone know if there is anywhere I can find this info? It's no biggy if I can't, as this is just an experiment I'm wanting to play with for a future concept...

    Thanks!
    Shelby

  2. #2
    Sr. Administrator Jack's Avatar
    Join Date
    Oct 2007
    Location
    Los Altos, CA
    Posts
    10,486
    Post Thanks / Like
    Images
    1031

    Re: Macro Lens Question (entrance pupil)

    This is a vast over-simplification, but...

    The problem is two-fold: one is entrance pupil moving, two is focal length is actually changing as you focus -- and IMHO problem #2 is far more significant than #1 will be. Change in EP will affect parallax where change in focal-length affects subject magnification. Both/either create ghosting in broad-range focus stacks.

    Pure IF lenses in theory do not move entrance pupil, but rather alter focal length directly -- effectively zooming out without altering focus for a net closer focus point. This should eliminate most of issue #1, but will exacerbate issue #2. Also, I'm not convinced that current "IF" macro lenses are 100% IF technology --- IOW I suspect that many use combinations of lens-group extension (albeit internal) and focal length changes to accomplish their focus.

    The advantage of fixed lens with bellows focus moving the sensor, is that while altering PoF, you are inversely compensating subject distance (it's measured from the sensor plane). At "normal" shooting distances the inverse compensation is very closely aligned with the rate of subject magnification change curve so the results are generally excellent. However, when you get into macro ranges, the proportionality curves diverge far more rapidly and the result will be less desirable as total focus range captured increases beyond a relatively narrow margin (like a few mm).
    Jack
    home: www.getdpi.com

    "Perfection is not attainable. But if we chase perfection, we can catch excellence."

  3. #3
    martin54
    Guest

    Re: Macro Lens Question (entrance pupil)

    Quote Originally Posted by Jack Flesher View Post
    This is a vast over-simplification, but...

    The problem is two-fold: one is entrance pupil moving, two is focal length is actually changing as you focus -- and IMHO problem #2 is far more significant than #1 will be..........................beyond a relatively narrow margin (like a few mm).

    Nice approach Jack, i liked that

  4. #4
    Sr. Administrator Jack's Avatar
    Join Date
    Oct 2007
    Location
    Los Altos, CA
    Posts
    10,486
    Post Thanks / Like
    Images
    1031

    Re: Macro Lens Question (entrance pupil)

    Thanks Martin, and welcome to GetDPI!
    Jack
    home: www.getdpi.com

    "Perfection is not attainable. But if we chase perfection, we can catch excellence."

  5. #5
    Workshop Member
    Join Date
    May 2008
    Location
    NYC
    Posts
    3,275
    Post Thanks / Like
    Images
    7

    Re: Macro Lens Question (entrance pupil)

    See also: http://www.captureintegration.com/20...extreme-macro/

    You'll probably need to physically remove any large foreground subjects on your long distance shots so that you have a "clean plate" from which to retouch in the areas which the foreground subjects "bloom" with their out-of-focusness.

    Or you can compose the shot so that all foreground elements are frame-bottom, all mid-ground elements are frame-middle, and all background elements are at frame-top so that when the near-ground objects are out of focus you don't have them overlap elements behind them.

    Doug Peterson (e-mail Me)
    __________________

    Head of Technical Services, Capture Integration
    Phase One Partner of the Year
    Leaf, Leica, Cambo, Arca Swiss, Canon, Apple, Profoto, Broncolor, Eizo & More

    National: 877.217.9870 *| *Cell: 740.707.2183
    Newsletter | RSS Feed
    Buy Capture One 6 at 10% off

  6. #6
    Senior Member mediumcool's Avatar
    Join Date
    Oct 2010
    Location
    South Australia
    Posts
    1,486
    Post Thanks / Like

    Re: Macro Lens Question (entrance pupil)

    Breathing definition

    Breathing video

    Longer video on Zeiss lenses (can’t supply direct URL because it’s built with Flash—ugh!) so you have to click on “The Brevis MP.1 Zeiss Lens Review and EX1 FIX Test Footage” down the page. 170MB FLV file.

    Fascinating for those who of us don’t usually shoot moving pictures.

  7. #7
    Senior Member yaya's Avatar
    Join Date
    Dec 2007
    Location
    London, UK
    Posts
    1,168
    Post Thanks / Like
    Images
    38

    Re: Macro Lens Question (entrance pupil)

    Quote Originally Posted by Shelby Lewis View Post
    This isn't MF specific, but I bet I'll end up using an MF lens... so I thought I'd pose it here... and you guys all know your lenses

    I have an idea for a shot that I'm wanting to do that uses stacked exposures.

    The catch... it stacks from macro to infinity. In order to pull this off, you need a lens where the entrance pupil doesn't move. This is usually done with a bellows in conjunction with focusing via camera-body-movement (for/aft)... which means a custom setup. The lens doesn't move at all. But there are a few lens, mostly on compact cameras, where the entrance pupil doesn't change as you focus. I'm wondering if the internal focusing slr lenses are included in this group...

    Does anyone know if there is anywhere I can find this info? It's no biggy if I can't, as this is just an experiment I'm wanting to play with for a future concept...

    Thanks!
    Shelby
    If your goal is to achieve some sort of infinite DOF and you have an idea of what the final frame/ composition is going to be like, then you can break it into "sections" like Doug has suggested and then you won't be limited to a single lens/ device but you will have to spend some time planing and calculating which lens to use for which section of the image

    Sounds like fun, good luck!!!
    Yair Shahar | Product Manager | Phase One | Mamiya Leaf
    e: [email protected] | m: +44(0)77 8992 8199 | yaya's blog

Tags for this Thread

Posting Permissions

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