Explanations on Challenging Issues in Camera Optics-Knowledge Encyclopedia-Shenzhen Kai Mo Rui Electronic Technology Co. LTD

Explanations on Challenging Issues in Camera Optics

Source：Shenzhen Kai Mo Rui Electronic Technology Co. LTD2026-08-08

Industrial machine vision systems are widely deployed in automated production, quality control, object inspection and other fields. Optical principles and lens selection constitute critical factors that guarantee system accuracy and efficiency.

1. Why Images Are Usually Not Sharpest at the Maximum Aperture

In many photography scenarios, maximum apertures (such as F1.2, F1.8) are adopted for low-light shooting or creating shallow depth of field. Nevertheless, images captured at maximum aperture often lack sharpness and even appear blurry. This phenomenon stems from spherical aberration and diffraction.

Spherical Aberration: At wide aperture settings, the lens accepts light over a large surface area. Incoming light rays cannot converge perfectly onto a single focal point, resulting in blurred imaging. The wider the aperture, the more noticeable the blurriness.

Diffraction: When the aperture is extremely narrow (e.g. F16 or smaller), light diffraction occurs. Light bends while passing through tiny openings and causes image softness. Although stopping down the aperture extends depth of field, fine detail sharpness will degrade.

Generally speaking, lenses deliver optimal sharpness at medium apertures such as F5.6 or F8. At these settings, the aperture is neither excessively wide nor too narrow, striking a good balance between light convergence and depth of field.

2. Why Some Macro Lenses Fail to Focus on Distant Objects

Macro lenses are ideal for capturing tiny targets such as industrial components and laboratory specimens, yet their focusing range differs from standard lenses. Many macro lenses can only focus at very close distances and cannot achieve focus on faraway objects. The root cause lies in the relationship between lens focal length and object distance (distance between the subject and the lens).

Object Distance & Image Distance: Focal length refers to the distance where light converges onto the image plane. For ordinary prime lenses with fixed focal length, image distance approximates focal length when the object distance is large. For macro lenses, the relationship between object distance and image distance becomes complicated when the subject moves extremely close to the lens, requiring internal lens element movement to achieve focus.

Furthermore, using extension tubes (to increase flange focal distance) further narrows the focusing range. Extension tubes effectively extend the lens’s focal length and enable focusing at closer working distances, but the lens will lose the ability to focus on distant subjects.

3. Finite Conjugate Lenses vs Infinite Conjugate Lenses

In machine vision, the imaging mode of a lens defines its applicable scenarios:

Infinite Conjugate Lenses: These lenses render sharp images of objects at infinity. Smartphone cameras and conventional photographic lenses fall into this category, capable of shooting distant scenes.

Finite Conjugate Lenses: These lenses only produce clear images within a limited working distance range, and are commonly used as macro lenses. For instance, macro lenses such as 100mm macro and 105mm macro support focusing between close and moderate distances, suitable for high-precision industrial inspection.

4. Differences Between Red Light and Blue Light in Industrial Applications

Within industrial machine vision, the choice between red and blue light directly affects image clarity and detail reproduction. Thanks to its shorter wavelength, blue light captures finer surface texture of objects and suits imaging micro-sized parts. Red light is widely adopted in numerous cases, especially for suppressing ambient light interference; it is cost-effective and well-matched with monochrome cameras.

Advantages of Red Light: Red light sources come at a lower cost and effectively mitigate interference from stray ambient light.

Advantages of Blue Light: Blue light delivers superior resolving power, ideal for high-precision industrial inspection with prominent advantages in fine detail reproduction.

5. Why ISO Is Rarely Mentioned in Industrial Vision

ISO is a familiar photography parameter used to adjust sensor light sensitivity. In consumer photography, higher ISO enhances light sensitivity yet introduces more noise and degrades image quality. However, in industrial machine vision, Gain generally replaces ISO.

Industrial cameras operate with fixed lighting sources and stable environments, making ISO adjustment far less essential than in consumer photography. Instead, industrial vision systems primarily rely on aperture and shutter speed to control exposure.

6. Why Higher Brightness Is Preferred for Light Sources

In industrial machine vision, high-brightness light sources help optimize imaging performance with the following benefits:

Shorter Shutter Speed: Sufficient illumination allows cameras to use faster shutter speeds, raising image acquisition speed to accommodate high-speed production lines.
Suppression of Ambient Interference: Intense lighting effectively overwhelms unwanted external ambient light and ensures consistent, clear images.
Extended Depth of Field & Improved Sharpness: Powerful lighting enables smaller aperture settings to increase depth of field and boost overall image definition, meeting strict precision requirements in industrial inspection.

7. What Is Single Pixel Quality

In industrial vision, pixel quality is directly related to the physical pixel size of the sensor. Sensors with larger pixel wells capture more light and reduce crosstalk between pixels, thus delivering clearer images. In contrast, sensors with tiny pixels are more susceptible to electromagnetic interference, generating higher image noise and compromising imaging quality.

For example, some industrial cameras feature 5µm × 5µm pixels, while smartphone cameras may only have 1.12µm × 1.12µm pixels. Larger pixel dimensions deliver superior image quality, which is critical for industrial applications demanding high-precision imaging.

Summary

A solid understanding of core knowledge including lens imaging principles, aperture effects, macro focusing mechanics and lighting selection allows industrial machine vision systems to perform efficient and accurate image processing and analysis in complex production and inspection environments. Proper application of optical principles not only improves imaging quality but also lifts overall production efficiency. Therefore, mastering these fundamentals is essential to maximize the performance of industrial vision systems when selecting equipment and tuning parameters.

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