Creating an anamorphic picture on a plane is very similar to drawing normally in perspective. The only difference is that the picture plane (the window in the description of perspective) is not perpendicular to the artist’s line of site.
This is how Jean Francois Niceron (who wrote the most comprehensive books on how to draw anamorphic pictures in the seventeenth century) showed how to create a plane anamorphosis.
The two pictures in the centre are the images to be made anamorphic using the grid method. You need to look from the right side of the picture to see them restored.
The geometry of the grid is as follows:
You should be able to see similarities in the construction for a perspective grid described in the explanation of perspective. You should also be able to relate to Niceron’s picture above. The anamorphic effect is to look at the image on the picture plane and have it appear to be a square grid, as if the square grid were placed in the position AB.
The original grid is shown at the bottom left. The blue and red lines at the bottom of the diagram are a plan view (looking from above) to explain the geometry. In this plan view the eye views the grid (which is seen as a red line), and the vertical lines of the grid are projected on the picture plane, which is the blue line through B and N. The line through the centre of the red line from E is perpendicular to AB, and EN is also perpendicular to this line.
To create the anamorphic grid. This description relates the plan and the view on the picture. In practice you only have to draw the lines Niceron used, so a shortened version is described below:
1. Choose a point D above N. Construct NC, so that CD equals EN.
2. Draw perpendiculars above the projected ends of the grid, that is B and W, and then for each projection from the blue line WN.
3. Join C to where the perpendicular line corresponding to the central line of the grid meets the horizontal blue line through D.
4. Extend this line to find point T and find R the point symmetrically above the blue horizontal line through D.
5. The line drawn in step 5 also finds the position of point S, and point U is found symmetrically.
6. RSTU form the outside of the grid and the vertical perpendiculars locate one set of the lines of the grid.
7. To find the equivalent of the horizontal set, join D to where the line CST meets each of the vertical lines.
To see the grid in the correct perspective, look from the right at a point E which is in front of the plane of the image. Niceron and others did not bother with this, but only used a simplified construction.
1. Choose a point D with a horizontal line through it.
2. Choose C above the point D at a distance equal to the distance in front of the paper from which to view the completed image.
3. Draw a line RT perpendicular to the blue horizontal line, so that R and T are symmetrically placed.
4. Join C and T and D to R and T. CT cuts DR at S and U can be found symmetrically from the position of S, or alternatively by erecting a perpendicular to the blue line from S.
5. Divide RT into equal divisions to match the number of points in the vertical direction in the grid.
6. Join these points to D to give the equivalent of the horizontal set of lines of the grid.
7. To find the vertical set, draw vertical lines (perpendicular to the horizontal blue line) where the line CST meets each of the lines.
Comparison with a perspective foreshortening
In a normal perspective picture the foreshortening means that the lines of the grid appear closer together the farther away the lines of the grid are to the viewer. In a plane anamorphic grid, the lines are equally spaced on the real grid but appear closer together on the part of the image nearest to the viewing point.
The shape of the image is always like this:
This means if you have an image like the portrait of Edward VI by William Scrots which is in the National Portrait Gallery in London, and you see the widest and most stretched part at the left, then you must look from the right.
In fact if you look closely at the frame on the right of the picture, then you can see a gap through which you need to look to see the portrait restored. An almost complete photographic restoration looks like this:
See the post on restoring anamorphic images by computer, on how NOT to restore the image by stretching.
The Passing Through Project
The artists Colin Wilbourn and Karl Fisher have created some public anamorphic art in the north east of England. The Passing Through sculpture (1997) is at St Peter’s Riverside in Sunderland. This is a plane anamorphosis. When you walk past it, the sculpture looks like an odd shape on the wall.
Holbein’s The Ambassadors
Perhaps the most famous painting with a hidden plane anamorphic object in it is the painting called The Ambassadors by Hans Holbein in the National Gallery in London.
For those who do know how to look at the painting, it has been described as all manner of puzzling objects from a banana to some sort of fish. If you look from the right hand edge of the painting, then you see it is a skull.