Which Lens Is Best for Your Imaging Sensor?

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If you are seeking out a camera, you might find yourself confused when reading the specifications of a camera about image sensors and their lenses. The purpose of image sensors, and how they work, are not fully understood by many people. In this article, we’re here to give you a quick and easy introduction to lens formats.

What is Lens Optical Format?

Typically, the size of the image sensor is expressed in terms of “inches,” however this really is not related to it and originates back to the era of “image tubes.” A sensor was considered to have a 1″ image format if it could fit into an image tube with a 1″ (inch) yoke. However, it’s crucial to focus on the “image circle,” which is the diagonal of the specific image sensor.

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The sensors that a lens can cover are determined by its image circle. It can be confusing with the variety of formats and lenses available. A lens can “cover” any formats smaller than the sensor size and film format it was intended to cover. Nevertheless, most lenses can’t handle formats that are larger than what they were designed to handle.

For instance, in order to completely cover approximately 1/3″, you need to have a lens format of at least 1/3″. Whether it is less than 1/3″, we would have vignetting issues.

Types of sensors and lens formats

There‌ ‌are‌ ‌two‌ ‌main‌ ‌types‌ ‌of‌ ‌image‌ ‌sensors (CCD and CMOS). The CCD gathers electrical charges in photosites, where each one stands in for a pixel, and transmits them to an amplifier before turning them into a digital image. CMOS, on the other hand, can process the data at each of its photosites.

There are many different types of lenses. Along with wide-angle and fish-eye lenses, there are generally entocentric or telecentric lenses. For near infrared, there are additionally specialised lenses.

However, since entocentric lenses are generally used in machine vision applications, we will only focus on them in this article. The aperture for the lenses and the sensor in typical entocentric lenses is fixed. The human eye contains the most prevalent entocentric lens.

Manufacturers of lens often come across sensor image format specifications such as 1/3″, 1/4″, 2/3″ and so on. Lenses come with a specification called ‘lens format’, that indicates the size, such as 1/3″, 1/4″, etc.

Design of Lens

To obtain the desired resolution, optical engineers consider a wide range of elements while manufacturing lenses. Any lens design will have a different lens performance depending on the working distance, ff/#, or wavelength range, either for a web camera or a high-resolution imaging system.

There is a perfect balance for each lens where the optimum results are attained. There will be a degradation in system performance if variables like working distance change. The speed at which this occurs depends on the system’s resolution.

Finding the right lens

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When it comes to formats and lens options, we have more choices than ever before. Increasing variety makes it more challenging. Before choosing your sensor size and lenses, it’s critical to understand the differences and what outcomes to expect.

The ideal format for every situation or job does not exist. Motion picture film formats consist of 8mm, 16mm, 35mm, and 70mm. In today’s digital cameras, we have many more formats than ever: 1/2″, 2/3″, Micro Four Thirds, Super-35mm, DX, APS-C, Full Frame, Vista Vision, and so on.

It is important to note that while all these formats require lenses, not all lenses are compatible with all formats. In addition, not all formats are appropriate for every application. 

What if I don’t have the appropriate lens format for my requirements?

Manufacturers of lenses are still coming up with new designs for lenses to match the evolving sensor market. However, you won’t always find a certain size format to go with the lens. In these situations, you simply need to make sure that the sensor size, as in the example above, is more than the lens format (image circle diameter).

Lens selection and Machine Vision System

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Understanding how camera sensors and image lenses interact is essential for implementing a machine vision system. An incorrectly coupled camera/lens combination may result in poor imaging and waste of time and money. Unfortunately, choosing which lens and camera to employ in any situation is challenging. Added sensors, and their properties make the situation more complicated.

The sensor image format and the lens format must be compatible. However, there are times when we do not receive an exact match, when we have lens specifications such as FOV, Focal length, resolution, and so on. When we don’t get a precise match, we should use the following rule of thumb.

  • Smaller format sensors can use larger format lenses.
  • Smaller format lenses cannot be used on larger format sensors.

How to choose the appropriate lens, in our opinion

Every year, new lens and sensor sizes appear, providing more options than ever before. With so many options at our disposal, we have a plethora of creative possibilities. However, now more than ever, we must ensure that all elements are considered before picking which format is ideal for a certain project.

You must understand which lenses work with which cameras and formats.  The answers to these questions make it much simpler for you to decide your choice on lens.

What is your project’s style? Do you require a camera and lens which are small in size? Are you being frequently in low-light conditions? Is your preference being prime lenses, zoom lenses or both? Do you have a preference like which is shallower or deeper depth of field? Is your set up time is limited or more? What is your financial situation?

  • For example, if you select the AR1335 Onsemi sensor-based camera module, we understand that the sensor size is 1/3.2″. The lens we choose should have a lens format of 1/3.06″ or larger, such as 1/3″ or 1/2.8″.
  • The AR0521 On Semiconductor sensor-based camera module is another example. In this case, the sensor is 1/2.5″ in size. We should work on picking a lens with a lens format of 1/2.5″ or above, such as 1/2.3″ or 1/2″, and so on.

Contact us-VADZO

Vadzo offers camera solutions for a broad range of sectors, including electrical, industrial, medical, retail, fleet management, asset management, smart homes, and kiosks. Among the services we offer are scanners, CCTV, CCD/CMOS, medical imaging, surveillance systems, machine vision, and night vision equipment.

We will provide you our recommendation for the best camera. From lens assembly and general design standards to budgets and timeframes, we will assist you with every step of your design.

We don’t need you to choose the wrong equipment so that you end up battling with it rather than working. More tools than ever are at your disposal, and it is up to you to choose the ones that are best for your project or else we can provide a unique camera solution for you to decide.  We have an array of large variety of standard cameras, assemblies and solutions, value-added services for component modification, and customized designs.

Get detailed dimensions and performance data for your project by contacting Vadzo’s application specialists.

 

Cheers,

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