What used to be the task of the film is now performed by the camera sensor. It records the image information and is therefore the most important part of the camera. Back then, film involved a lot of chemistry and physics. Today, with digital cameras, the chemistry has been replaced by electronics which, if you want to go into more depth, is just as complex.
Structure of a sensor
I would like to briefly explain the basic structure of a camera sensor without going into too much technical detail. A camera sensor consists of many light-sensitive pixels. Each of these pixels records the information that reaches it through the lens within the exposure time. In simple terms, this means that a larger sensor can collect more information than a smaller sensor and therefore produces a better image.
Why being tall is an advantage
Sometimes bigger is better, especially when it comes to collecting information. A light-sensitive pixel has a certain size depending on the sensor. The number of pixels present on a sensor is indicated by megapixels. A few years ago, 12 megapixels were still a real highlight, today 16 – 24 megapixels are an acceptable measure, professional cameras sometimes have 36 megapixels and more.
My point is this. 24 megapixels on a large sensor gives a better result than 24 megapixels on a small sensor. The reason is obvious: in order to accommodate the same number of pixels on a smaller surface, the pixels have to be significantly smaller, which leads to a decrease in dynamic range (contrast range) and an increase in image noise, especially in low light conditions.
To get the same number of pixels on a smaller sensor, they have to be smaller. This increases the noise behavior in difficult lighting conditions.
However, a larger sensor area also allows camera manufacturers to place significantly more pixels there, i.e. to increase the resolution without having to compromise on image quality. For comparison, a full-frame sensor could have 36 megapixels, with the same size, compared to an APS-C sensor with 16 megapixels. That’s more than twice as many pixels, so quite a big difference.
A full-frame sensor fits significantly more pixels with the same size
To be fair, however, it must be said that the technology for all sensors is already well advanced. An APS-C sensor is not necessarily inferior to a full-frame sensor. I use some cameras with an APS-C sensor and they have completely different qualities.
Mega Megapixel
How many megapixels a photographer needs is a matter of debate. A few years ago, people were proud to own an 8 megapixel camera. Even more pixels on the sensor would only increase the noise behavior and unnecessarily increase the file size. Today, a full-frame sensor, e.g. from the Nikon Z 7, has 45.7 megapixels.
However, higher resolution always means more data volume and more computing power. On the other hand, of course, you have the option of printing the images even larger or cropping them more without the image becoming too small.
It depends very much on the intended use. If you just want to look at your pictures on your computer or make prints in the usual standard formats, you don’t necessarily need such high resolutions.
What should have become clear, however, is that the megapixel specification alone does not provide a reasonable indication of the expected quality. 12 megapixels, as currently advertised for an iphone 12, have to share the space on a very small sensor, so they are correspondingly small. The megapixel specification should therefore always be considered in conjunction with the sensor size.
Advantages of a large sensor
The full-frame sensor is based on the size of the original 35mm film format of a 35mm camera. Accordingly, most people are still familiar with the designation of the focal lengths of lenses. A photo taken with a 50 mm lens on a full-frame camera would be a telephoto shot with the same focal length on an ASP-C sensor, which corresponds to a 75 mm focal length on a full-frame camera. The extension factor or crop factor of 1.5 from ASP-C to full format is noticeable here.
Comparison of full-frame sensor to ASP-C sensor. Due to the smaller format of the ASP-C sensor, the same lens has an extension factor of 1.5 – 50mm with a full-frame sensor becomes 75mm with an ASP-C sensor.
Sensor sizes at a glance
There are a large number of sensor sizes. I have picked out the most common ones.
The gray area shows the difference to full format.
| Camera size | Cameras and manufacturer (example) | |
|---|---|---|
| Full format | 36.00 x 24.00 mm | Nikon D850, Sony Alpha 7 iii, Canon EOS R6 |
| APS-C, DX | 23.70 x 15.60 mm | Nikon D500, Fujifilm X-T5 |
| APS-C | 22.20 x 14.80 mm | Canon PowerShot G1X |
| Micro Four Thirds 4/3″ | 17.30 x 13.00 mm | |
| 1″ | 13.20 x 8.80 mm | |
| 1/1.7″ | 7.60 x 5.7 mm | |
| 1/2.3″ | 6.17 x 4.55 mm |
