Question

Consider the following statements: I. In aerial photogrammetry the 'filter' is placed in front of the lens to: II. Reduce the effect of atmospheric haze. III. Protect the lens from dust. IV. Provide uniform light distribution over the format. Which of the above statements is/are correct

• A. \( \text{I and II only} \)
• B. \( \text{II only} \)
• C. \( \text{I and III only} \)
• D. \( \text{I, II and III} \)

Hint:

Think of filters like sunglasses for the camera, reducing glare (haze) and protecting the lens.

Answer 1

The Correct Option is D

Filters are placed in front of the lens in aerial photogrammetry for several reasons: \begin{itemize} \item II. Reduce the effect of atmospheric haze: Certain filters can selectively block wavelengths that are strongly scattered by atmospheric particles, thus improving image clarity. \item III. Protect the lens from dust and scratches: A filter acts as a sacrificial protective layer for the expensive camera lens. \item I. While not the primary purpose, some specialized filters can be used to influence the spectral characteristics of the light reaching the sensor, which can indirectly help in reducing the effect of atmospheric haze by selecting specific spectral windows. Providing uniform light distribution (IV) is typically a function of the lens design and potentially anti-vignetting filters, not the standard filters used for haze reduction and lens protection. \end{itemize} Therefore, statements I, II, and III are correct.