15 - 463: Computational Photography

Project 0: The Vertigo Shot - by Goutham Mani

Overview

For this project, several series of images were captured using an Olympus E-500 DSLR camera. Two lenses were used with this camera, one whose focal length could be varied from 14mm to 45mm and another whose focal length could be varied from 45mm to 160mm.

To produce the dolly zoom effect, the camera was set to minimum zoom and placed near the subject. Then the camera was moved away from the subject while increasing the zoom so that the subject appeared to have a constant size. When the first lens (14mm - 45mm) was at maximum zoom, it was replaced with the second lens (45mm - 160mm) which had deeper zoom and could go up to a narrower field of view.

Several sequences of images were shot, all in the 4th floor of the CIC (Collaborative Innovation Center) building. The three series of images that were chosen for display here feature a Yoda doll, a T-Rex doll and a set of game cards as subjects.

For the series titled Yoda's revenge (Series 1), the camera was placed on a tripod, in order to to maintain height and orientation between pictures. This was facilitated by the fact that Yoda himself was placed on a table at a convenient height. For the series titled Game Cards (Series 2), the cards were placed upright on the floor with the help of a support. These shots were taken by the photographer while crouching down and trusting his sight to maintain alignment and orientation.

Series 1: Yoda's revenge

Act 1: T-Rex sneaks up behind Yoda

Act 2: Yoda stabs T-Rex with his lightsaber


Series 2: Game cards


"Bells and Whistles" #1: Animated GIFs

Series 1: Act 1 - T-Rex sneaks up on Yoda



Series 1: Act 2 - Yoda stabs T-Rex with a lightsaber



Series 2: Game Cards



"Bells and Whistles" #3: Computing Field of View


The trash can is 1.25 feet wide (d = 1.25ft). The camera was placed 3.7ft away for the minimum zoom shot, and 9.7ft away for the full-zoom shot (using the 14mm - 45mm lens).

We use the equation FOV = arctan( d / 2f ) to calculate the field of view.

For the minimum zoom shot, d = 1.25ft, f1 = 3.7ft. Therefore FOV1 = arctan( d / 2f1 ) = arctan( 1.25 / 7.4 ) = 9.59 degrees.
For the maximum zoom shot, d = 1.25ft, f2 = 9.7ft. Therefore FOV2 = arctan( d / 2f2 ) = arctan( 1.25 / 19.4 ) = 3.69 degrees.

But, the trash can covers only 11.1% of the total picture in both cases. So, both FOV1 and FOV2 need to be multiplied by (100/11.1) in order to get the actual Field of View of the camera.

FOV1 = (100/11.1) * 9.59 = 86.4 degrees = Field of View at minimum zoom
FOV2 = (100/11.1) * 3.69 = 33.2 degrees = Field of View at maximum zoom

Difficulties Encountered

The biggest difficulty I encountered with this project was maintaining the size and orientation of the subject across multiple frames. This difficulty was particularly evident when shooting Series 2 (Game Cards), where the cards were placed on the ground and I had to employ a crouching position in order to take the photos. Using a tripod for Series 1 (Yoda's Revenge) made things considerably easier, and consequently I was able to take many more shots(17 frames in Series 1: Act 1 as opposed to just 6 frames in Series 2) in order to achieve a smoother transition between frames.