1. Why does the lens focal length affect the field of view and image size?

· PrincipleThe lens focal length refers to the distance from the optical center of the lens to the imaging plane (such as the camera sensor). The shorter the focal length, the greater the angle at which light rays travel from the edges of the lens to the imaging plane, resulting in a wider field of view—just like when we use a wide-angle lens to observe our surroundings, we can capture a broader scene. However, objects in the image appear relatively smaller. Conversely, the longer the focal length, the more concentrated the light rays become, narrowing the field of view—much like using a telescope to view distant objects, where only a smaller area is visible, but objects in the image appear relatively larger.

· Give an example.When shooting landscapes, using a short focal length (wide-angle) lens allows you to capture vast scenes—such as majestic mountains and expansive grasslands—in their entirety. On the other hand, when shooting close-ups—like capturing the intricate details of flowers or close-ups of people’s faces—a long focal length (telephoto) lens enables the subject to occupy a larger proportion of the frame, highlighting fine details.

2. How does aperture size affect depth of field and exposure?

·  In terms of depth of fieldThe larger the aperture (i.e., the smaller the f-number—e.g., an aperture of F1.8 is larger than F5.6), the shallower the depth of field. This is because, with a large aperture, only objects within a very narrow range around the focal plane can be captured sharply, while the background and foreground become blurred, thereby highlighting the main subject. For example, when shooting portraits, a large aperture can keep the subject in sharp focus while blurring the background, creating a soft and aesthetically pleasing visual effect. On the other hand, a small aperture (a larger f-number) deepens the depth of field, allowing objects from near to far in the scene to remain relatively sharp—a feature that makes it ideal for capturing landscapes and other scenes where overall clarity is essential.

·  Exposure方面The aperture directly controls the amount of light entering the camera. A large aperture allows more light to pass through the lens and reach the sensor; under otherwise identical conditions, this results in a brighter image, making it ideal for shooting in low-light environments. By contrast, a small aperture restricts the amount of light entering the camera, resulting in a relatively darker image. It’s typically used in well-lit conditions or when seeking specific effects—for example, when photographing flowing water, using a small aperture along with a slow shutter speed can give the water a silky, smooth texture.

Why does distortion occur, and how can we reduce its impact?

· Cause of occurrenceDistortion refers to the geometric deformation between the actual image and the ideal image. It is primarily caused by limitations in the optical design and manufacturing processes of lenses. Common types of distortion include barrel distortion and pincushion distortion. Barrel distortion typically occurs in wide-angle lenses, where the edges of the image curve outward, resembling the shape of a barrel; pincushion distortion, on the other hand, usually appears in telephoto lenses, with the edges of the image curving inward, similar to the shape of a pillow.

· Reduction methodAs for the distortion caused by the lens itself, some high-end lenses reduce distortion by employing more complex optical designs, special lens materials, and advanced manufacturing techniques. In addition, during post-image processing, professional image-editing software can be used to apply correction tools that partially rectify distortion. However, such corrections may result in some loss of image detail.

4. What is color difference, and how can it be avoided or reduced?

· DefinitionChromatic aberration refers to the phenomenon where, due to differences in the refractive indices of light rays of different colors as they pass through a lens, these rays fail to focus precisely on the same plane, resulting in colored fringes or color blurring at the edges of the image. Chromatic aberration is primarily divided into axial chromatic aberration (also known as longitudinal chromatic aberration) and magnification chromatic aberration (also known as lateral chromatic aberration). Axial chromatic aberration manifests as different colors of light focusing at different positions along the optical axis; magnification chromatic aberration, on the other hand, refers to the varying magnification factors of different colors of light on the imaging plane.

· Avoidance or Mitigation MeasuresIn lens manufacturing, the use of special materials such as low-dispersion glass and fluorite can effectively reduce chromatic aberration. Additionally, some lenses employ a multi-element lens design, in which the lenses work together to compensate for each other, thereby minimizing chromatic aberration. In terms of camera settings, selecting appropriate shooting parameters—such as avoiding scenes with high contrast—can also help mitigate the impact of chromatic aberration on images. During post-processing, professional image software can correct chromatic aberration by adjusting tools like color balance and dispersion correction, thus enhancing image quality.

5. What are the effects of sensor size on image quality?

· Regarding sensitivity:Generally speaking, larger sensors have relatively larger individual pixel areas, enabling them to collect more light and thus delivering better sensitivity in low-light conditions with less noise. For example, compared to an APS-C sensor, a full-frame sensor has larger pixel areas at the same pixel count, allowing it to produce cleaner images at higher ISO settings.

· In terms of dynamic rangeLarge-size sensors typically offer a higher dynamic range, enabling them to capture details in both brighter and darker areas simultaneously. This means that in high-contrast scenes, cameras equipped with large-size sensors can better preserve information in both highlights and shadows, avoiding overexposure in bright areas or complete blackening in dark areas.

· Depth of field control sideUnder the same focal length and aperture conditions, a larger sensor can produce a shallower depth of field, which is more conducive to highlighting the subject, blurring the background, and creating a professional photographic effect. In contrast, to achieve the same depth-of-field effect with a smaller sensor, one would need either a larger aperture or a longer focal length—both of which may face certain practical limitations during actual shooting.