1. Problem Background How do we subjectively evaluate the quality of an image during image assessment? The most obvious criteria are **image clarity and transparency**, which determine the evaluator's first impression of image quality. How should we understand image clarity and transparency? This is the focus of this article. 2. Problem Analysis a. On Image Clarity Before describing image clarity, it is necessary to understand two concepts: **sharpness** and **resolution**. What is resolution? Resolution refers to the ability to distinguish spatial details, also known as resolving power, discriminating power, analyzing power, and resolving capability. It is the ability of an image to clearly reproduce the fine details of the photographed scene. The higher the resolution, the clearer and more delicate the image. If extremely adjacent lines can be separated, the image is considered to have a high resolution.

In photography, acutance specifically refers to the sharpness of image details and edges. High acutance means the image possesses more distinct and clear details and edges, rendering the overall image more vivid and eye-catching.

Therefore, acutance describes the transition speed of image information at boundaries. High acutance results in rapid information transitions, making boundaries clearly visible. What is clarity? Clarity is the combined manifestation of resolution and acutance, that is, Clarity = Acutance + Resolution. Resolution determines how close adjacent details can be distinguished, while acutance determines the sharpness of detail edges. See the figure below: A. Good resolution, poor acutance B. Poor resolution, good acutance C. Excellent resolution and acutance D. On Image Transparency What is transparency? In Chinese, it is interpreted as "bright and clear". In an image, it refers to a comprehensive visual and psychological experience, including rich and bright color and tone layers, translucent and profound sense of space, and clear and distinct object outlines. Although there are various causes of poor transparency, they present the same symptoms: the photo appears muddy and hazy. Muddiness refers to impure colors, low saturation, and excessive noise and color casts in the photo. Haziness means dull tonal rendition, characterized by an indistinct subject, insufficient details, and inadequate acutance and contrast.