Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 28

Thread: Aperture placement

  1. #11

    Join Date
    Jul 2004
    Location
    Tucson, Arizona
    Posts
    4,196

    Re: Aperture placement

    Quote Originally Posted by Mark Woods View Post
    I think the discussion of front and rear nodal points refer to the center of the respective elements. The nodal point of the lens has to do with perspective and movement. We encounter this issue all the time in visual effects when shooting miniatures. The aperture can be placed in any number of positions determined by the lens designer. The vignetting caused by an aperture I would think relates to the image circle, and if the lens vignettes the image circle is too small for the format. I hope this helps. :-)
    I'd beg to differ... each individual cell may have its own nodal points, but the entire system has a front and rear nodal point as well. And as Len noted, they can be outside the physical body of the lens on some designs, and inside on others. Regardless of the design or where the nodal points are, the correct pivot point should be the front entrace pupil at the optical axis.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  2. #12
    Big Negs Rock!
    Join Date
    Mar 2000
    Location
    Pasadena
    Posts
    1,079

    Re: Aperture placement

    Hello Mark,

    I believe that's what I said in the first sentence. And the second sentence also agrees with what you posted. :-)
    Mark Woods

    Large Format B&W
    Cinematography Mentor at the American Film Institute
    Past President of the Pasadena Society of Artists
    Director of Photography
    Pasadena, CA
    www.markwoods.com

  3. #13

    Join Date
    Jul 2004
    Location
    Tucson, Arizona
    Posts
    4,196

    Re: Aperture placement

    Quote Originally Posted by Mark Woods View Post
    Hello Mark,

    I believe that's what I said in the first sentence. And the second sentence also agrees with what you posted. :-)
    My fault; my brain was fried today! (End of the third quarter grading day...) When you said:

    Quote Originally Posted by Mark Woods View Post
    Nodal point relates to the relationship of the taking lens to the world where the pan/tilt don't shift the image in relationship the foreground to the background.
    ...I somehow jumped to panning and stitching, as some of my students have been doing that lately. That's where things rotate around the front entrance pupil. Duh, I is stoopid!
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  4. #14

    Join Date
    Nov 2007
    Location
    Nuremberg Germany
    Posts
    1,051

    Re: Aperture placement

    Quote Originally Posted by Mark Sawyer View Post
    Well, the nodal points are among the cardinal points, but there are othe cardinal points, so the terms aren't quite interchangeable.
    There are also the front and rear focal points, the vertexes of front and rear lens and the focal plane. But if the lens is used in air the principal planes coincidences with the nodal points.

    To illustrate the determination of the nodal points after Moessard I will made a drawing, but later this day, it's nearly 3 a. m. here. Sorry

    Peter
    I'm not weird. I'm limited edition.

  5. #15
    Big Negs Rock!
    Join Date
    Mar 2000
    Location
    Pasadena
    Posts
    1,079

    Re: Aperture placement

    Mark,

    I'm grading papers today too. That's why I have so much time for these discussions. :-) That Oslo paper is killer. Too bad I'm Mac based or I'd download the educational software. It would come in handy when I do my lecture on lenses at the American Film Institute. Might be worth getting a cheap Dell to get it. Oh well....
    Mark Woods

    Large Format B&W
    Cinematography Mentor at the American Film Institute
    Past President of the Pasadena Society of Artists
    Director of Photography
    Pasadena, CA
    www.markwoods.com

  6. #16
    Big Negs Rock!
    Join Date
    Mar 2000
    Location
    Pasadena
    Posts
    1,079

    Re: Aperture placement

    Mark, where do you teach?
    Mark Woods

    Large Format B&W
    Cinematography Mentor at the American Film Institute
    Past President of the Pasadena Society of Artists
    Director of Photography
    Pasadena, CA
    www.markwoods.com

  7. #17

    Join Date
    Jul 2004
    Location
    Tucson, Arizona
    Posts
    4,196

    Re: Aperture placement

    I'm just a crappy old high school teacher at Marana High, in the backwoods of Arizona!

    It's kinda fun though... I have some really dedicated kids who are doing 4x5 and 8x10, even a bit of wet plate work is starting. Others, I have to threaten and cajole to get a crummy cell-phone pic out of...

    Glad you liked that Oslo pdf. It's one of my favorites!
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  8. #18
    Big Negs Rock!
    Join Date
    Mar 2000
    Location
    Pasadena
    Posts
    1,079

    Re: Aperture placement

    Hey Mark, with all the digital stuff I have to teach, the Fellows want to shoot on film. They love it and we teach both captures. They're totally blown out with my 8x10 contact prints and love to shoot 35mm Motion Pic capture. I'm very proud to teach at the Conservatory that is considered #1 for Cinematographers on the planet. (And our faculty is modest too. ;-))
    Mark Woods

    Large Format B&W
    Cinematography Mentor at the American Film Institute
    Past President of the Pasadena Society of Artists
    Director of Photography
    Pasadena, CA
    www.markwoods.com

  9. #19
    45-57-617
    Join Date
    Oct 2006
    Location
    Toowoomba, Queensland
    Posts
    427

    Re: Aperture placement

    So! Its not as easy as I thought.

    Firstly, I think I'm sorry I mentioned the technical term 'nodal' ... it seems it was a cardinal sin !!!

    But seriously, thanks guys. Yes I have a lens in mind, an old magic lantern lens for a start. It may be a Petzval I don't know.

    Where do I go from here? Must I get accurate measurements and then learn a computer simulation program ? It is beginning to be very complicated. I was hoping to cut it in two and be done ...

    Rgds,

  10. #20

    Join Date
    Nov 2007
    Location
    Nuremberg Germany
    Posts
    1,051

    Re: Aperture placement

    Quote Originally Posted by Steve McLevie View Post
    Where do I go from here? Must I get accurate measurements and then learn a computer simulation program ? It is beginning to be very complicated. I was hoping to cut it in two and be done ...
    Steve, forget the computer simulation program. For this you would need not only to know the curvatures and thickness of ever lens but also refractive indexes and Abbe's numbers of the glass used. Also this old glasses are not in modern glassmaker's catalogues and also not in the data-bank of the programs.

    So measure and note the distances of the lenses, diaphragms etc. Than make the threads a little bit longer to get the possibility of alignment by turning the barrels against each other.

    Peter
    I'm not weird. I'm limited edition.

Similar Threads

  1. Replies: 13
    Last Post: 19-Mar-2009, 22:39
  2. Apple Aperture for LF?
    By Rory_5244 in forum Digital Processing
    Replies: 4
    Last Post: 20-Jun-2007, 16:06
  3. Giant Lens Aperture Problem
    By Andrew van Bommel in forum Lenses & Lens Accessories
    Replies: 3
    Last Post: 24-Sep-2004, 19:01
  4. Two different aperture readings from Copal #0 shutter--which one is correct?
    By Rafil Kroll-Zaidi in forum Lenses & Lens Accessories
    Replies: 4
    Last Post: 3-Sep-2004, 07:27
  5. Scals of Zeiss Protar aperture
    By Cheng Lu in forum Lenses & Lens Accessories
    Replies: 4
    Last Post: 18-Jul-1999, 03:24

Bookmarks

Posting Permissions

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