The objective of this lab is to understand and experiment with the "camera obscura" principle, which translates to "darkroom" in Latin. This lab involves building two cameras—one large and one small—to explore the effects of aperture size and camera size on brightness, sharpness, and image quality. Additionally, the report compares mathematical principles and practical observations.

ECE516: Pinhole Camera Lab Report

Name: Tianyu Fan

Student ID: 1011836453

Objective

The objective of this lab is to understand and experiment with the "camera obscura" principle, which translates to "darkroom" in Latin. This lab involves building two cameras—one large and one small—to explore the effects of aperture size and camera size on brightness, sharpness, and image quality. Additionally, the report compares mathematical principles and practical observations.

Introduction

The concept of a pinhole camera is rooted in the principle of "camera obscura." A small aperture allows light to project an inverted image onto an opposing surface. This lab revisits this ancient imaging technique through experimentation and mathematical analysis.

The optimal pinhole diameter is determined by balancing classical optics as well as modern optics. The formula for optimal aperture diameter is:

d=c sqrt(f⋅λ)

Where:

1. d: Optimal pinhole diameter
2. f: Focal length (distance from pinhole to the image plane)
3. λ: Wavelength of light (550 nm for green light, to which human vision is most sensitive)
4. c: Constant related to the Rayleigh criterion (1.56 to 2 for this experiment)

Materials and Methods

1. Large cardboard box (50 cm × 50 cm × 60 cm)
2. A7C2 camera with adjustable settings (18 mm Focal Length)
3. Black tape
4. White paper (projection screen)
5. Scissors

Experiments

1. Large Pinhole Camera

1. Construction:
2. A large cardboard box with two Holes:
3. Big Hole: For inserting the DSLR lens to capture results.
4. Small Hole: A pinhole of approximately 0.8 mm ; Then expand the hole to see the effects of a hole that is too large. The interior has a white paper taped on the opposite side as a screen.
5. Calculations:
6. Using f=50 cm, c=1.56 to 22, and λ=550nm:
7. d=1.56⋅0.5⋅550×10−9=0.82 mm
8. d=2.0⋅0.5⋅550×10−9=1.04 mm
9. Settings for Image Capture:
10. DSLR settings: ISO 12800, 1/3-second shutter speed, f/2.8, 28mm lens.

Results:

The following images were captured:

1. Camera setup with the large cardboard box
2. View of Toronto through the large camera
3. Interior view of the camera with projection screen
4. View of Toronto through the large camera

2. Small Pinhole Camera

1. Construction:
2. A small cardboard box with a pinhole aperture of 0.16 mm. The camera directly used its sensor to capture light without an external projection surface.
3. Calculations:
4. Using f=18 mm,c=1.56, and λ=550nm:
5. d=1.56⋅18×10−3⋅550×10−9=0.16 mm
6. d=2.0⋅18×10−3⋅550×10−9=0.20 mm
7. Settings for Image Capture:
8. DSLR settings: ISO 6400, 1/30-second shutter speed.

Results:

The following images were captured:

1. Camera setup with the camera
2. View of Toronto through the small camera
3. Camera setup with the camera
4. A selfie captured using the small camera

3. Practical Camera with Magnifying Glass

1. Construction:
2. For this third experiment, the same large cardboard box (50 cm × 50 cm × 60 cm) was used, but instead of using a pinhole, a small lens (5× magnifying glass) was attached to the front of the box. A white paper screen was placed at the back (up to 60 cm away) as the imaging plane. This setup repurpose the box into a more practical camera using a converging lens.
3. Calculations:
4. A magnifying glass labeled “5×” usually corresponds to a focal length of about 33 cm (0.33 m), we can plug in the value to the thin lens equation:
5. 1/f=1/do+1/dif
6. where:
7. ff is the focal length of the lens,
8. dodo​ is the distance from the lens to the subject (effectively very large for distant objects),
9. didi​ is the distance from the lens to the image plane (up to 50 cm inside the box).
10. We can calculate that dodo​ is approximately 33cm.
11. Settings for Image Capture:
12. DSLR: ISO 800, 1/60-second shutter speed, f/2.8.
13. Projection: The lens-based arrangement delivered a bright, focused image of an LED lamp seen by eye or with the DSLR.
14. Results:
15. By adjusting the white screen’s position (around 25–35 cm from the lens), the LED lamp was projected clearly and brightly onto the screen.
16. Compared to a pinhole of similar diameter, the magnifying glass gathered more light and produced a brighter, sharper image.

Discussion

Comparison of Large and Small Cameras

1. Image Quality:
2. The large camera produced brighter and sharper images due to its larger sensing area.
3. The small camera captured softer images with lower detail, limited by the pinhole and sensing area.
4. Aperture Size and Brightness:
5. The large camera allowed for a larger aperture which can collect more light and creating a brighter image. Whereas the small camera required a smaller aperture, limiting its light collection ablities.
6. Camera Sensor vs. Phone Camera:
7. The DSLR sensor (35mm format) outperformed a phone camera due to its larger size, enabling it to gather more light and produce higher-quality images. The larger sensor also provided better dynamic range and depth of field. This experiments also shows this principal.

Conclusion

This lab demonstrated the fundamental principles of pinhole imaging, where we built cameras and experimenting with aperture sizes. The large camera demonstrated better performance in brightness and sharpness, while the small camera is limited by reduced aperture and sensor size. The experiment also shows the application of the mathematical principles of optimal aperture design.