Understand the Raspberry Pi High Quality Camera with M12 Lens and Mount
Interchangeable lenses officially introduced to Raspberry Pi cameras
The Raspberry Pi is a versatile minicomputer for makers to build all kinds of projects, but its official camera modules are less so. Great as the V1 and V2 cameras are, they lack flexibility on the optical performance side. You don’t have many options for the official camera modules, except the sensitivity for infrared.
We can argue that it’s not the Raspberry Pi’s responsibility to meet the camera-related requirements from every customer, because their focus is to build better communities and produce motherboards. Therefore, in the time of V1 cameras, third-party manufacturers like Arducam took quick actions to build Pi cameras with interchangeable lenses. When those third-party cams hit the market, the customers had access to better manual focus, wider angle, or switchable IR-cut filter. After the IMX219 camera is out, we’ve also provided solutions to enhance the optical performance of the V2.
However, the Raspberry Pi foundation does not completely play down the camera lineup. To respond to the most wanted features, here comes the Raspberry Pi High Quality Camera with higher resolution and access to C/CS-Mount lenses. 7 years after the release of the first camera module, a mounting system for interchangeable lenses is finally introduced to the official Raspberry Pi camera modules.
M12 Lens – The popular candidate not selected by the RPi foundation
Before the HQ camera was out, Arducam had been pushing the customization of Pi camera modules for several years. We want to make the most of the OV5647 and IMX219 by bringing more features to them, so you can try better camera projects on the Raspberry Pi.
The key to flexibilities of lenses is the lens mount. A mainstream mount can accommodate various ready-to-use lenses on the market. The video surveillance market is one of the biggest consumers of lenses, in which M12 lenses and C/CS-Mount lenses are used most.
So Arducam started out with Pi camera modules with M12 Mount Lenses (featuring Arducam B0031) and CS-Mount Lenses (featuring Arducam B0032), which gained us a lot of customers. They both contribute a lot to our sales, but the M12 lenses are more popular on the market, possibly because they are more compact and cost-effective. As the demand continually increases, we’ve even built two M12 lens kits which includes multiple lenses in one box to cover the spectrum of demands.
If it were Arducam to build the third Raspberry Pi camera module, we will build one with an m12 lens. When it finally comes, we are surprised that the popular M12 lenses are not selected, instead, the RPi High Quality Camera is ready for C/CS-Mount Lenses. Another surprise is that they are not officially selling the lenses but have recommended two from another little-known reseller.
Get Arducam M12 lenses ready again for the C/CS-Mount era
Will the C/CS-Mount introduced to the HQ camera put an end to M12 lenses? We don’t think so. Since M12 lenses have already been widely used before the Raspberry Pi High Quality camera is out, people have got used to it. We have many m12 lenses that produce decent pictures and win popularity among our users. After the High Quality camera is released, we’ve received many inquiries on using m12 lenses on it, so it’s time to get M12 lenses ready again for the latest Raspberry Pi camera.
However, we need to fix some issues when it comes to using M12 lenses on the HQ camera. The first one is a lens mount to accommodate an M12 lens, and the second is the matching relationship between m12 lenses and the Sony IMX477 sensor.
The lens mount issue is easier to fix, and Arducam happens to own many M12 to CS-Mount adapters. A wonderful thing about the C and CS-Mount is that they are threaded mounts, which means that it’s easier to design and use an adapter just like how the lenses on them are easily interchangeable. With the help of the M12 to CS-Mount adapter, it becomes possible to physically thread an M12 lens into the CS-Mount, so step one is accomplished.
Now we are in the second phase. Successfully fastening the M12 lens to the camera module does not guarantee you success, because there are also optical issues other than the mechanical ones. This is where the lens optical format and image sensor format come in. The image sensor format describes the size of the image sensor, and usually we want the lens optical format larger than the image sensor format, so the lens exposes light to the whole image sensor. If you are not clear about how that works, you can check this page.
The image sensor format of the IMX477 is relatively larger than most of those used on board cameras, at 1/2.3”. On the contrary, most M12 lenses offer a smaller optical format, usually at 1/2.5”, 1/2.7”, 1/3” or even 1/4”. Therefore, many M12 lenses cannot expose the whole IMX477 image sensor to light, leaving unexposed pixels on the edge and thus dark surrounding on the final picture. The answer to that is to find M12 lenses with a large optical format.
Make M12 Lenses great again on Raspberry Pi HQ camera
Well, facts speak louder than words. If we want to know whether an M12 lens is compatible with the RPi HQ camera, just try it. So, we’ve tested all our M12 lenses on the camera one by one to see if it results in a decent picture, and what’s the Field of View on it. Some of those lenses have been packed into another lens kit. It could be quite time-consuming, but I believe the result will save time for our customers.
Once we’ve proven that you can use some M12 lenses on the Raspberry Pi HQ camera, we can look at how they might outperform the C/CS lenses. Firstly, it’s the size. Generally, M12 lenses are smaller and more compact than C/CS-Mount lenses, so it’s better for space- and weight-constraint applications, such as drones. Anyway, you would not be willing to carry a bulky and heavy C or CS-Mount lenses to fly.
Secondly, M12 lenses tend to be more cost-effective. Although we can claim that the C/CS lenses can offer a better image quality, that depends on the extra money you’ve spent. Common M12 lenses are adequate for most applications.
Another benefit we’ve found from the M12 lenses is that you can find wide-angle M12 lenses more easily than the C/CS-Mount. Speaking of wide-angle, we are not talking about the 6mm focal length level wide-angle, because that really produces a relatively narrower field of view compared to a fisheye lens.
That’s just our work for now. We will continue to provide more M12 lens options for the Raspberry Pi High Quality Camera while expanding the C/CS-Mount product line at the same time. After all, our goal is to offer more choices to the consumers so they can make better and smarter purchases for the Raspberry Pi High Quality Camera lens.