A guide to making a digital sensor for a pinhole camera

Rewritten content: Data analysis report release

Source: IEEE

In recent years, people’s interest in pinhole photography has continued to grow, and related activities have also become more and more popular. More and more, pinhole cameras began to receive attention in various commercial and international photography events

Pinhole cameras in The optics have some incomparable features. First, it has virtually unlimited depth of field, which means that all objects in the camera's field of view are clearly visible, no matter how close or far they are from the camera. Secondly, pinhole cameras will not produce distortion problems such as chromatic aberration. However, the shortcomings of pinhole cameras are also very obvious. Pinhole cameras, whether purchased or made by yourself, require the use of film or photo paper, which quickly increases the cost of taking photos. Additionally, there is a certain delay between taking a picture and seeing the result

Perhaps the most important thing about a pinhole camera is that it is based on film, and taking a photo requires a long exposure time. Even in bright sunlight, this often takes a few seconds, increasing the likelihood that the act of filming will be ruined or interrupted.

In the opinion of this blogger named David, the use of digital sensors seems to be able to solve the above problems. He has a $10 ESP32-Cam board that integrates a Wi-Fi enabled ESP32 microcontroller, a microSD card slot, LED indicators, and interfaces for multiple low-cost image sensors

The camera module he used is OV2460. When used with ESP32-CAM, the maximum resolution can reach 1,600 x 1,200 pixels

During the production process, He also connected a microswitch to one of the board's general input/output pins and wrote some firmware to use the switch as a shutter control and save the image to a microSD card

Additionally, he programmed the LED to flash some error codes when something went wrong, such as trying to write to a full microSD card. Since there are many software libraries available for the ESP32-CAM, it didn't take long to write this glue code

On the hardware side, he used a Glowforge laser cutter to create a wooden box , used to store the sensor, ESP32-CAM board and shutter switch. Among them, the key pinhole components are designed to be detachable, so that the focal length can be adjusted by replacing different components, thereby adjusting the camera's field of view

This also makes pinhole photography possible. Flexibility of Disassembling the Lens

However, nothing comes for free. Pinholes do vary in size, and the price for all these digital advantages is having to make camera pinholes smaller than in traditional pinhole cameras. This is because the sensor is much smaller than the film frame: the sensor width is 4 mm, while the film width is 35 or 120 mm

To ensure that the full image produced by the pinhole falls on the surface of the sensor , the sensor must be closer to the pinhole than the film. When calculating the optics needed we discovered we needed a smaller pinhole

David first found a thin piece of brass and punched one in it with a center punch dent. Then sand the brass from the other side until just breaking through the dent. This creates a nice little hole. However, there is no doubt that this is a lot of work and some pinholes need to be prepared when testing the camera

Pictures

In the end, David chose to use aluminum foil. He tried stretching some aluminum foil and piercing it with a needle. Typically, this results in larger holes. However, if you place aluminum foil on a plastic surface on your workbench and gently press the needle into the foil, the plastic will only allow the tip of the needle to penetrate the foil

Although this method is not very reliable, it allows us to make many pinholes more quickly and easily and find the ideal diameter pinholes

You’re done, now It’s time to pick up the camera!

David took his camera to a local lighthouse and connected the battery. Due to the high sensitivity of the image sensor, exposure times of only a fraction of a second were required, and he was also able to download the photos from the microSD card and view them in the field. David discovered that these The photos taken retain the unique luminous appearance of traditional pinhole photography, which can be said to be very successful

In his opinion, there are still some areas where the entire camera can be optimized. For example, coating the inside of interchangeable optics with some matte black material can reduce internal reflections and prevent blurry photos. Also consider adding an LCD screen so you can see exactly what the camera is capturing in real time. The ESP32 controller has enough computing power to drive a small display

Get ready, David can’t wait to look forward to WPPD in April next year!

Let’s give it a try. Welcome to share your experience in the comment area~

Related reports:

The content that needs to be rewritten is: https://spectrum.ieee.org/a-digital-pinhole-camera

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