Grid Math

I just went over the Point Pelee diorama and measured the spacings between the grid marks.  They range from 5″ at the center line to 5 3/8″ at the corners and 4 7/8″ at the side.  This makes sense because the closest distance to the viewer is at the sides of this diorama and therefore the grid squares would have to be the smallest there.  At the corners where the distance is the farthest from the viewer, the squares would have to be larger.  Wilson’s grid makes all  points on the grid related in this way-perfectly sized to the distance the wall is from the viewer.

So I now know some of the coordinates that can help me come up with a pretty good guess of what lens he used on his camera and the spacings he laid over his slides to make this diorama.  Backing up…Wilson’s grid is ingeniously related to his reference photos such that the viewer of the diorama is in the same relation (or angle of view) to the diorama background as Wilson was standing at the site taking his photos.   It’s as though when you stand in front of a Wilson diorama, you get to stand in his shoes in the landscape.  Wilson was producing virtual reality long before there ever was such a thing.

The mechanics of the grid are as follows:

The distance from the central viewing point to the center of the diorama wall (in this diorama that distance is 54″) and the distance between the first and second vertical (5″) is equal to the focal length of the camera and the grid spacing on his slide.

I know he used either a 50 mm or a 35 mm lens which into inches translates respectively as 2″ or 1 3/8″.  The grid for his slides was either 1/10″ or 1/8″  In this case the math indicates he used a 35mm lens, probably a stereo camera, with 1/8″ spacings over his slides. [35mm or 1 3/8″ X 5″=6.875   6.875 divided by 54=.127 (very close to 1/8″ or .125)]  Double click on the scans below and you should be able to read them:

A letter from James Perry Wilson to Thanos Johnson 2 years after he finished the Point Pelee diorama in which he describes his gridding method. Jan 4, 1966

Explore posts in the same categories: Wilson Dioramas

5 Comments on “Grid Math”

  1. Sean Murtha Says:


    Does this mean that you HAVE found a grid under the Point Pelee Painting? (try saying that 10 times fast!)


    • Yes, the grid marks were there all along, but I was looking for vertical lines extending below the painting. There are just pencil marks visible on the right side below the painting. the marks on the left have been painted over. This is a new mystery how he was able to contain the grid under the area painted and why. This grid was not done with plumb bobs-otherwise we would see lines.

      Should I make this more clear in the blog? Michael PS Yale Bulleting wrote up the exhibit and focused half of a page on the blog. The blog tallies how many people visit the site and on Friday there were 48 visits to the site! or were 40 of those yours???

      • Sean Murtha Says:

        Not 40. Maybe 8. Joyce, who was really bummed not to be at the reception, probably accounts for the rest.


  2. Donald Kratz Says:

    I need to study the grid system.

    • The grid is fairly simple-it contracts as the background wall gets closer to the viewer and expands as the wall is farther away. The part that is amazing is that Wilson mathematically related his reference photos to the painted background by the focal length of the camera to the viewing distance to the background wall. These two innovations made his dioramas unique and in a different league than the others.

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