Results 1 to 5 of 5

Thread: How Polaroids Work

  1. #1

    How Polaroids Work

    I've shot 8x10, 4x5, spectra and i-zone polaroids.

    Out of curiousity, just how do these things work?

    The "professional" sheet film variety, I understand roughly. Expose the negative. Cover. Move the positive over the negative (4x5 in the camera when lowering the envelop. 8x10 in the processor). Roll. Rollers break the pod and spread the chemicals. Direct contact equals positive print. And this part is a chemical process (no light involved). Peel apart and discard negative (unless type 55).

    How about the "automatic" "consumer" polaroids? How does the exposed surface (top) also become the printed surface? Is it a light process (ie. same as traditional darkroom) or a chemical process (such as the "professional" polaroids)

    Anyone with good links or can explain this to me please?

  2. #2

    Join Date
    Nov 2003
    Posts
    1,217

    How Polaroids Work

    It is basically the same process as for "professional polaroids". There is a negative which is exposed, it is put in contact with the paper with chemical pods between and rollers spread the chemicals to develop both the negative film and the print at the same time. But there has to be some trickiness in order to end up with a print which is not reversed left to right.

    I have a polaroid back for my Horseman Technical camera. It took me a while to figure out just how it must work and I had to disassemble an old package of film to finally get it straight.

    It is hard to describe in words. Try www-unix.oit.umass.edu/~jpalma/pack_film_details.html which has some diagrams.

  3. #3

    Join Date
    Sep 2003
    Location
    Santa Cruz
    Posts
    134

    How Polaroids Work

    You can also look here for an explanation.

  4. #4

    Join Date
    Nov 2003
    Posts
    1,217

    How Polaroids Work

    Peter,

    Your link explains how the film and print are developed together, but it doesn't deal with the issue of getting the orientation right. Looking at the picture there, one would assume that the film is exposed with the print paper in back and then the two are developed together by pulling through the rollers. If you did that, you would capture what you see when you look back at the image from the lens. But that has reversed orientation. To get the orientation right, you have to look at the image from the other side. In order to accomplish that, after exposure of the emulsion, you have to bring the print paper in front of the emulsion before developing them together. If it were there to start, it would block the formation of the negative image.

    Let me explain a bit by what I mean by orientation. This is confusing because the gg image, viewed from the back is usually described as being upside down and reversed left to right. That is true in a certain sense, but it can be misleading. It is better described as being rotated by 180 degrees. Orientation, meaning the innate distinction between left and right, is best described by how letters look. Orientation is reversed if letters appear backwards. If you rotate the image, you don't reverse the orientation. If you have a transparent image and you turn it around, no matter how you do it, or you look at it from the other side, you do reverse the orientation. So the gg image viewed from the back does not have reversed orientation, but viewed from the front it does. The usual description of the gg image is true in the following sense. Imagine you have captured the film image and you are looking at it just as it appears on the gg glass. If you turn it over by rotating it vertically about its horizontal midline, it will now be right side up, but turning it over will have reversed orientation. Letters will be backwards. Now turn it around by rotating it horizontally about its vertical midline. That will now reverse the orientation again to get it back to the correct orientation. But it would of course be easier just to rotate it by 180 degrees to produce the same effect.

  5. #5

    How Polaroids Work

    Peter, thanks, exactly what I was after.

    Leonard, that's more than a thorough explanation. Thanks for taking the time. Completely off-topic, but here's a stumper for you. Why are we (and all animals) built laterally symetrical, but up-down-wise, we're not even remotely symetrical. Gravity?

Similar Threads

  1. Why Are My Polaroids Sharper Than My Proofs?
    By Scott Rosenberg in forum Darkroom: Film, Processing & Printing
    Replies: 12
    Last Post: 3-May-2004, 10:26
  2. Chocolate polaroids
    By tim atherton in forum Darkroom: Film, Processing & Printing
    Replies: 5
    Last Post: 20-Sep-2003, 11:17
  3. Scanning 4x5 Polaroids
    By Bill_1856 in forum Darkroom: Film, Processing & Printing
    Replies: 2
    Last Post: 22-May-2002, 14:33
  4. Polaroids In Below Freezing Temps?
    By Gary Albertson in forum Darkroom: Film, Processing & Printing
    Replies: 2
    Last Post: 8-Dec-2000, 15:05
  5. Grain on my Type 52 Polaroids?
    By Josh Wand in forum Cameras & Camera Accessories
    Replies: 3
    Last Post: 10-Apr-2000, 20:36

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
  •