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DL for CV · Edges, corners & SIFT features

20 questions · 39 marks · 3 papers

Answer key

Indian Institute of Technology Madras

BS Degree Programme · Examination & Study Paper

Deep Learning for Computer Vision

Edges, corners & SIFT features

Official Paper

Examination Instructions & Guidelines

Solve on notebook/paper first before checking solutions.
MCQ: Exactly 1 option is correct. Negative marking applies.
NAT: Numerical response. No negative marking.
Scientific calculator allowed for all calculations.
Official answer key is sealed at the end of this sheet.

Quiz 1 · 26 Oct 2025 (AN)Quiz 1

Q1MCQ2 Marks·Choose one option
Asked 2 times Key ↓
Choose the correct sequence for Canny edge detection: 1. Smooth with Gaussian 2. Compute gradient magnitude & direction 3. Non-maximum suppression 4. Double thresholding (strong/weak) 5. Edge tracking by hysteresis
1. A2 → 1 → 3 → 4 → 5
2. B1 → 2 → 3 → 4 → 5
3. C1 → 3 → 2 → 4 → 5
4. D3 → 1 → 2 → 5 → 4
Q2MCQ2 Marks·Choose one option
Asked 2 times Key ↓
Correct order of SIFT stages is:
1. AOrientation→ Descriptor → Localization → Extrema Detection
2. BExtrema Detection → Localization→ Orientation→ Descriptor
3. CExtrema Detection → Descriptor → Localization → Orientation
4. DNone of these
Q3MCQ2 Marks·Choose one option
Key ↓
In double thresholding, T_(high) = 120, T_(low) = 50. A pixel with gradient magnitude 45 is classified as:
1. AStrong edge
2. BWeak edge
3. CNon-edge
4. DAmbiguous
Q4MCQ2 Marks·Choose one option
Asked 3 times Key ↓
1. A1→iii, 2→i, 3→v, 4→iv
2. B1→i, 2→iii, 3→v, 4→ii
3. C1→iii, 2→iv, 3→v, 4→ii
4. D1→iii, 2→iv, 3→ii, 4→v
Q5MCQ2 Marks·Choose one option
Key ↓
1. A1→iii, 2→i, 3→ii
2. B1→ii, 2→iii, 3→i
3. C1→iii, 2→ii, 3→i
4. DNone of these
Q6NAT3 Marks·Write the number
Key ↓
Your answer:
Q7NAT3 Marks·Write the number
Key ↓
Your answer:
Read the passage below, then answer Q8–Q9
In Canny, increasing the high threshold tends to (a) _______________ false positives and (b) ____________ false negatives.
Based on the above data, answer the given subquestions.
Q8Short answer1.5 Marks·Write the answer
Key ↓
Enter the correct answer for Blank (a) ________________ NOTE: Enter the exact answer without any extra space in the beginning or at the end.
Your answer:
Q9Short answer1.5 Marks·Write the answer
Key ↓
Enter the correct answer for Blank (b) ________________ NOTE: Enter the exact answer without any extra space in the beginning or at the end.
Your answer:
Read the passage below, then answer Q10–Q11
During non-maximum suppression, comparisons are made along the gradient (a) _____________ to keep only local (b) _______________.
Based on the above data, answer the given subquestions.
Q10Short answer1.5 Marks·Write the answer
Key ↓
Enter the correct answer for Blank (a) ________________ NOTE: Enter the exact answer without any extra space in the beginning or at the end.
Your answer:
Q11Short answer1.5 Marks·Write the answer
Key ↓
Enter the correct answer for Blank (b) ________________ NOTE: Enter the exact answer without any extra space in the beginning or at the end.
Your answer:
Read the passage below, then answer Q12–Q13
The gradient of an image I points in the direction of the most rapid change in intensity. Taking image derivatives accentuates (a) ______________ frequencies and hence amplifies noise, since the proportion of noise to signal is larger at (b) _______________ frequencies. The common solution is to smooth the image prior to computing gradients.
Based on the above data, answer the given subquestions.
Q12Short answer1.5 Marks·Write the answer
Key ↓
Enter the correct answer for Blank (a) ________________ NOTE: Enter the exact answer without any extra space in the beginning or at the end.
Your answer:
Q13Short answer1.5 Marks·Write the answer
Key ↓
Enter the correct answer for Blank (b) ________________ NOTE: Enter the exact answer without any extra space in the beginning or at the end.
Your answer:

End Term · 31 Aug 2025 (FN)End Term

Q14MCQ2 Marks·Choose one option
Key ↓
Choose the correct matching:
1. A
2. B
3. C
4. D
Q15MCQ2 Marks·Choose one option
Asked 3 times Key ↓
1. A1→ iii, 2→ iv, 3→ i, 4 → ii
2. B1→ iii, 2→ i, 3 → ii, 4 → v
3. C1→ iii, 2→ iv, 3→ v, 4 → ii
4. D1→ iv, 2→ iii, 3→ i, 4 → ii
Q16MCQ2 Marks·Choose one option
Asked 2 times Key ↓
Identify the correct sequence of steps in a Canny edge detection pipeline. Steps are listed below: 1. Compute gradient magnitude and direction 2. Connect individual components 3. Smoothen the image 4. Threshold into strong, weak, or no edge 5. Gaussian Filter and Hysteresis 6. Non-maximum suppression 7. Apply derivative to get edges
1. A6→ 1→ 4→ 5 → 2
2. B3→ 1→ 6→ 4 → 2
3. C3→ 5→ 1→ 4 → 2
4. D6→ 3→ 5→ 7 → 2
Q17MCQ2 Marks·Choose one option
Asked 2 times Key ↓
Which of the following is the correct sequence of steps of the SIFT algorithm? 1. Using the Taylor series expansion of the scale-space function, lo-calize the key points. 2. Estimate the orientation of keypoints using the local image gra-dients. 3. Find the edge points using the eigenvalues of the Hessian and reject these points. 4. Find a raw SIFT descriptor vector using the gradient orientations of the neighborhood around the key points. 5. Detect extreme points in scale space using an approximation of the Laplacian of Gaussian.
1. A5, 2, 1, 3, 4
2. B5, 1, 3, 2, 4
3. C1, 3, 2, 4, 5
4. D1, 5, 3, 2, 4
Q18MCQ2 Marks·Choose one option
Asked 2 times Key ↓
1. A1→ iii, 2→ iv, 3→ ii, 4 → i
2. B1→ i, 2→ iv, 3 → iii, 4→ ii
3. C1→ iv, 2→ iii, 3→ ii, 4 → i
4. D1→ iii, 2→ i, 3 → ii, 4 →v

End Term · 31 Aug 2025 (AN)End Term

Q19MCQ2 Marks·Choose one option
Asked 3 times Key ↓
You are designing an edge detection pipeline for noisy grayscale images. For each of the following goals, choose the most appropriate filter or method: 1. Smooth out noise before any edge detection step 2. Detect edges by finding zero-crossings in the second derivative 3. Highlight regions with a strong intensity gradient 4. Perform basic edge detection with a simple directional gradient filter
1. A1 → Gaussian filter, 2 → Laplacian of Gaussian, 3 → First derivative of Gaussian, 4 → Sobel operator
2. B1 → Sobel operator, 2 → Gaussian filter, 3 → Laplacian of Gaussian, 4 → First derivative of Gaussian
3. C1 → First derivative of Gaussian, 2 → Sobel operator, 3 → Gaussian filter, 4 → Laplacian of Gaussian
4. D1→Laplacian of Gaussian, 2→First derivative of Gaussian, 3→Sobel operator, 4→Gaussian filter
Q20MCQ2 Marks·Choose one option
Asked 2 times Key ↓
1. A1→ iii, 2→ iv, 3→ ii, 4 → i
2. B1→ i, 2→ iv, 3 → iii, 4→ ii
3. C1→ iv, 2→ iii, 3→ ii, 4 → i
4. D1→ iii, 2→ i, 3 → ii, 4 →v

Official Key

Master Answer Key & Explanations

Official answer keys from IIT Madras BS past papers. Click any question to review.

Reveal Key

Q1B

Q2B

Q3C

Q4C

Q5A

Q68

Q7-0.515

Q8decrease

Q9increase

Q10direction

Q11maxima

Q12high / higher / large / largest

Q13high / higher / large / largest

Q14D

Q15C

Q16B

Q17B

Q18D

Q19A

Q20D

Questions and answer keys are reproduced from the official IIT Madras BS papers. Topics and repeated question types are BTechi’s own grouping. BTechi is not affiliated with IIT Madras.