Time-lapse photography in Raspberry Pi - Mini Project: Build & Apply

Time-lapse photography

📖 Scenario: You have a Raspberry Pi with a camera module. You want to create a simple program that takes photos at regular intervals to make a time-lapse video later.

🎯 Goal: Build a Python program that takes a photo every few seconds and saves it with a unique filename.

📋 What You'll Learn

Create a list of filenames for photos

Set an interval time in seconds

Use a loop to simulate taking photos at each interval

Print the filenames of photos taken

💡 Why This Matters

🌍 Real World

Time-lapse photography is used to capture slow changes like plants growing or clouds moving by taking photos at set intervals.

💼 Career

Understanding loops and timing is important for automation tasks in programming and working with hardware like Raspberry Pi.

1

Create a list of photo filenames

Create a list called photo_filenames with these exact strings: 'photo1.jpg', 'photo2.jpg', 'photo3.jpg', 'photo4.jpg', 'photo5.jpg'.

Raspberry Pi

# Create a list called photo_filenames with 5 photo names
# Your code here

Hint

Use square brackets [] to create a list and put the photo names as strings inside.

2

Set the interval time

Create a variable called interval_seconds and set it to the number 10 to represent the time between photos in seconds.

Raspberry Pi

photo_filenames = ['photo1.jpg', 'photo2.jpg', 'photo3.jpg', 'photo4.jpg', 'photo5.jpg']
# Create a variable interval_seconds and set it to 10
# Your code here

Hint

Just write interval_seconds = 10 to set the interval time.

3

Simulate taking photos with a loop

Use a for loop with the variable filename to go through each item in photo_filenames. Inside the loop, write a comment # Simulate taking photo to represent taking a photo.

Raspberry Pi

photo_filenames = ['photo1.jpg', 'photo2.jpg', 'photo3.jpg', 'photo4.jpg', 'photo5.jpg']
interval_seconds = 10
# Use a for loop to go through photo_filenames
# Your code here

Hint

Write for filename in photo_filenames: and indent the comment inside the loop.

4

Print the photo filenames taken

Inside the for loop, write print(f"Photo taken: {filename}") to show the photo filename taken.

Raspberry Pi

photo_filenames = ['photo1.jpg', 'photo2.jpg', 'photo3.jpg', 'photo4.jpg', 'photo5.jpg']
interval_seconds = 10
for filename in photo_filenames:
    # Print the photo filename taken
    # Your code here

Hint

Use print(f"Photo taken: {filename}") inside the loop to show each photo name.

Practice

1. What is the main purpose of using time-lapse photography with a Raspberry Pi camera?

easy

A. To capture images at set intervals to show slow changes quickly

B. To take a single high-resolution photo

C. To record live video continuously

D. To stream video over the internet in real-time

Solution

1. Step 1: Understand time-lapse photography concept

   Time-lapse photography captures photos at regular intervals to speed up slow processes.

2. Step 2: Compare options with concept

   Only To capture images at set intervals to show slow changes quickly describes capturing images at intervals to show slow changes quickly.

3. Final Answer:

   To capture images at set intervals to show slow changes quickly -> Option A

4. Quick Check:

   Time-lapse = interval photos showing slow changes fast [OK]

Hint: Remember time-lapse means interval shots, not continuous video [OK]

Common Mistakes:

• Confusing time-lapse with video recording
• Thinking it captures only one photo
• Assuming it streams live video

2. Which of the following Python code snippets correctly sets a 5-second delay between photos in a Raspberry Pi time-lapse script?

easy

A. sleep.time(5)

B. time.wait(5)

C. delay(5)

D. time.sleep(5)

Solution

1. Step 1: Recall correct syntax for delay in Python

   The correct function to pause execution is time.sleep(seconds).

2. Step 2: Check each option

   Only time.sleep(5) uses time.sleep(5), which is correct syntax for 5 seconds delay.

3. Final Answer:

   time.sleep(5) -> Option D

4. Quick Check:

   Delay = time.sleep(seconds) [OK]

Hint: Use time.sleep() to pause, not time.wait() or delay() [OK]

Common Mistakes:

• Using time.wait() which does not exist
• Swapping module and function names
• Using undefined delay() function

3. What will be the output of this Raspberry Pi time-lapse code snippet?

from picamera import PiCamera
import time
camera = PiCamera()
camera.start_preview()
for i in range(3):
    camera.capture(f'image_{i}.jpg')
    time.sleep(2)
camera.stop_preview()

medium

A. No images saved because preview blocks capture

B. Only one image named image_2.jpg saved after 6 seconds

C. Three images named image_0.jpg, image_1.jpg, image_2.jpg saved with 2 seconds delay between each

D. SyntaxError due to incorrect f-string usage

Solution

1. Step 1: Analyze the loop and capture calls

   The loop runs 3 times (i=0,1,2), capturing images named image_0.jpg, image_1.jpg, image_2.jpg.

2. Step 2: Understand timing between captures

   After each capture, the program waits 2 seconds before next capture, so images are spaced by 2 seconds.

3. Final Answer:

   Three images named image_0.jpg, image_1.jpg, image_2.jpg saved with 2 seconds delay between each -> Option C

4. Quick Check:

   Loop 3 times + capture + sleep(2) = 3 spaced images [OK]

Hint: Loop count = number of images; sleep controls delay [OK]

Common Mistakes:

• Thinking only last image is saved
• Confusing preview with capture blocking
• Assuming f-string causes error

4. Identify the error in this Raspberry Pi time-lapse code snippet:

from picamera import PiCamera
import time
camera = PiCamera()
for i in range(5):
    camera.capture('image_i.jpg')
    time.sleep(1)

medium

A. Missing camera.start_preview() before capture

B. The filename 'image_i.jpg' does not change, overwriting images

C. time.sleep() cannot be used inside a loop

D. PiCamera() must be imported after time module

Solution

1. Step 1: Check filename usage inside loop

   The filename is a fixed string 'image_i.jpg', so each capture overwrites the previous image.

2. Step 2: Verify other code parts

   start_preview() is optional; time.sleep() works in loops; import order does not matter here.

3. Final Answer:

   The filename 'image_i.jpg' does not change, overwriting images -> Option B

4. Quick Check:

   Filename must vary to save multiple images [OK]

Hint: Use f-strings or string formatting to vary filenames [OK]

Common Mistakes:

• Thinking start_preview() is mandatory
• Believing time.sleep() can't be in loops
• Assuming import order causes error

5. You want to create a time-lapse video from 10 photos taken every 3 seconds using Raspberry Pi. Which approach correctly combines capturing images and creating the video?

hard

A. Capture images with time.sleep(3) in a loop, then use ffmpeg to combine images into a video

B. Capture images continuously without delay, then rename files manually before video creation

C. Use time.sleep(10) between captures and combine images with a photo viewer

D. Capture images with delay, then upload them directly to YouTube without video creation

Solution

1. Step 1: Understand time-lapse capture timing

   Photos must be taken every 3 seconds, so time.sleep(3) in a loop is correct.

2. Step 2: Combine images into video

   ffmpeg is a common tool to combine sequential images into a video file.

3. Final Answer:

   Capture images with time.sleep(3) in a loop, then use ffmpeg to combine images into a video -> Option A

4. Quick Check:

   Interval capture + ffmpeg video creation = correct workflow [OK]

Hint: Use delay in capture loop + ffmpeg for video [OK]

Common Mistakes:

• Skipping delay causing fast captures
• Using photo viewer instead of video tool
• Uploading images without video creation