The fact is that any mobile smartphone is a box containing a group of gadgets/modules, and the camera is just only one out of them.
To save battery power and to attain the best efficiency of the main processor, usually many gadgets, including the camera will be kept in off mode - the camera turns into operation only when you trigger it on - right? (when you touch the camera icon/App).
Without getting into a lot of technicalities, let us look at the steps in which the photo is captured by the camera in your mobile. The whole process explained is for fully automatic mode for still image.
Level 1 consideration:
The light enters the camera through the lens and falls on the image sensor.
Once you point at your object and touch on the screen, the process of focusing completes.
After focusing, once you touch the shutter button, the image is captured.
Then the captured image is processed and saved into your mobile’s memory, which you view as the photo.
Having said that in simple words, the actual process is much more complex. Let us have a slightly deeper understanding of the process. Once the camera module is switching on:
Level 2 consideration:
The light enters through the lens and falls on the image sensor. This is a continuous process when your camera is on, which consumes a good amount of power (battery).
The images in front of the lens will be captured by the image sensor in its temporary memory of the camera module. This image is processed & that is what is seen on the display of the mobile, continuously. (the “View Finder” in Camera)
Although you just touch your object on the screen of your mobile to focus, it is another complex process. (which will be explained later).
After focusing, when you touch the shutter button, the data in the temporary memory is immediately recorded/saved as a photo.
Level 3 consideration:
Your image sensor is made up of pixels and each pixel is a light-sensitive cell (photoelectric cell) which produces electrical signals.
Since your object contains different colours (& intensity), the light falling on the image sensor also will produce different signals. This varying type of electrical signal is known as an analogue signal.
While the camera is in the standby mode, the electric signal flows only in the temporary memory of the camera module.
The moment you touch the shutter button, the sensor sends the captured scene/signal in the temporary memory to the Image Processor, which converts the analogue signal into digital data. For this purpose, the camera module of mobile uses a separate processor, temporary memory & a set of other circuitries.
Finally, this digital data is converted into a displayable (say JPEG) Image file and then only one can view the photo.
That is:Your image which falls on the sensor produces an analogue signal which is converted into digital data & then made into a visible JPG file.
Hope the basic details are clear; if anyone has any doubt, kindly tag me & comment down; I also welcome other technical LGs to creatively take part in the discussions.
I am a (double) postgraduate in Electronics Engineering & Technical Consultant; as many of you know, along with photography, I spare time to share my knowledge.
@TravellerG This is interesting topic to me. Lately I discussed about how camera works and how earth observation satellite works. It turns out that they both work the same way. Thank you so much for sharing this interesting knowledge with us.
@TravellerG Oh sorry, I mean I discussed it with my colleagues. Basically there are sensors on satellite and they have filter to receives specific spectrum. So each pixel has a value of spectrum reflectance and with many spectrum frequencies, we can combine them into an image. Something like that. I’m sorry that I’m not an expert. But in the end, my colleagues and I agree that images from camera and observatory satellite work the same way.
Thank you so much for sharing this interesting knowledge with us.