photography lesson 1 – understanding cameras

Understanding cameras tutorial How the sensor works analogy for digital photography beginners Understanding cameras and how they work should be the first step in your learning process and will help […]

Understanding cameras tutorial

How the sensor works analogy for digital photography beginners

Understanding cameras and how they work should be the first step in your learning process and will help you to take good quality photos that will make you stand out as an amateur or as professional photographer.

In this tutorial we will explain in very simple terms the process of taking a picture with a camera. We will explain the concept of exposure, underexposure and overexposure.

This is destined for digital photography beginners who are looking to start using a camera

We can compare the camera with a human eye. There is a strong similarity how the image is captured. I would like to use few analogies just for an easier understanding of how the camera works:

Camera is like human eye with two important optical elements:

–       Cameras sensor

“the back of the eye or retina”– it comes in a wide variety quality and few sizes. Sensors are coming in a variety of sizes and qualities. Without getting too technical in this subject, a larger sensor is always better, as it captures more information. The sensor has another very important characteristic which can be controlled and that is sensitivity (ISO – International Standardization Organisation). Think about the ISO like the sensitivity to your eye, after getting used in the dark, suddenly you see a flash and the after effect. A more sensitive eye, needs more time to recover.

understanding camera

–       Camera lens

“ the eye crystalline lens” – is the main focusing mechanism. The light gets through it in order to be projected on the sensor. The lens has the responsibility to allow light in the camera and finding and focusing on the subject

All cameras follow the same principles. The shutter opens and closes in front of the sensor to allow the image to be projected through the lens. One cycle defines one “exposure”

In order to understand the sensor and how this works I am proposing an analogy I personally like. You can imagine the sensor as a large sports field filled with buckets on the ground,  next to each other and the light as the rain falling from the sky  and filling these buckets.

For those of you who have an understanding what light is, as a combination of magnetic wave and a flow of particles (photons), I would propose to compare it with a rain. The amount of light can be compared with the amount of rain.

A good exposed picture is formed when all the buckets are half full. The buckets are empty (dark) they star the get filled during exposure. If the exposure is too long, that means more rain filling the buckets – more light impressing the sensor clusters. If the buckets are filled and overflow, that means an overexposed image where the buckets cannot be seen any more due to the large amount of water.

Please refer to our youtube video to see an attempt to visualize the exposure. TBA

I always keep this in mind in order to explain myself what happens in the camera. I apologize if this description is just intuitive and does not reflect how a sensor works in reality but I am trying to make it more accessible for everyone.

So, when buckets are empty, there is dark, and they are filled, there is light – underexposure and overexposure.

It took me a while to really understand these concepts. Experienced photographers were always talking about correct exposure or incorrect exposure, but I could not figure it out where a correct exposure starts and where it ends. I was varying my camera settings up and down, and the difference was too small for me to understand the “correct exposure” concept.

Just to re-iterate the concept of exposure in comparisons with rain on a field with buckets on the ground. The Exposure starts when the curtains are being opened, the rain starts to fall filling the buckets. If the rain does not last long enough, and the curtains close, there is not much water in the buckets, and there is not much information captured on the sensor. That is the case of under-exposure.

When the rain is stopped by the shutter at the right time, when the buckets are half filled, that makes it a good exposure. When the rain is too long, the water overflows and that means too much light hits the sensor whitening the image beyond recognition – this is overexposure.

Another aspect of this exposure, is the rain – light is not even and there are parts of the field getting more and parts of getting less rain- light. This is more often as any images will have lighter or darker parts.

After the exposure, the sensor (field of buckets) analyses the information received and send it to the processor (or the brain if we can compare it with the human eye).

The field of buckets is in reality a map of pixels where each individual pixel receives a certain amount of light, but not only the amount of light, but it receives a certain colour which represents the frequency of the light. So every pixel gets a specific amount of light with a specific colour.

In conclusion an image is basically a map of pixels (squares) with different colours. These colours are described by numbers by the modern computers. This map of pixels translates into a big list of group of 3 numbers (each colour is described by 3 numbers – reflecting 3 components of red, green, blue: I am not going to get into more technical details than this to stay within reasonable levels of understanding) and this is how a computer will record it.

I hope my analogy is helpful for those who are just starting out in digital  photography and it will help you to visualize. It did help me to control the images and take control of the camera.

understanding cameras should be the first step in your photography journey before you can actually attempt on playing with the settings


About Christian Tudor

professional photographer, main editor at Academy of Photography and