Understanding the number of Pixels and Sensor Sensitivity

"Do we need a higher Pixels camera?", "Image quality depends on the number of Pixels?", "Larger Sensor got higher Pixels than smaller Sensor?"...and etc. Most people ask this questions when they choosing a camera. 

One day, my friend complaint that he got cheated by the salesman because the salesman told him the model he bought is the highest Pixels in the market, at that moment. When he tried to capture sceneries, the pictures is not clear while he zoom in the LCD monitor. He tried to focus, change the Depth of Field, changing to lower of Pixels and tested with different ISO speeds and etc but the result still same, dissatisfy. 

Well, what he bought is "higher number of Pixels" but not "higher Sensitivity Sensor" ( or we called it a "Large Sensor"). I remember once awhile in the market, companies were competing for "higher Pixels" camera because most people want a "higher Pixels" instead of a "higher Sensitivity Sensor" (they might not even know what is higher sensitivity sensor). Most people thought "higher Pixels" camera is so important.

Actually, even if a smaller sensor has the same number of Pixels as a larger sensor. A larger sensor are more sensitive, resulting in a higher image quality than a smaller sensor. Therefore, higher image quality does not depends on the number of Pixels only.

Assume we have 2 same sensitivity sensors but different number of Pixels, which one will have a higher image quality? Well, of course is the higher number of Pixels. But, compare a 10 Mega Pixels in higher sensitivity sensor and 12 Mega Pixels in lower sensitivity sensor, I bet the first choice is better, for sure :)

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How does ISO speeds work?

What is ISO speeds? ISO speeds is a setting determine the quality of picture. Do not get me wrong, quality does not equal to number of Pixels.

Traditional film camera do not have ISO speeds setting. It is a setting for digital camera's Sensor (A Sensor is a "film" of Digital Camera).  Low ISO speeds obtain higher picture quality, and high ISO speeds obtain lower picture quality.

Some digital camera have a lower ISO speeds, and higher ISO speeds up to ISO 12800.

As you can see, the picture get blurred by increasing the ISO speeds. But It is not "Blur", it is "Noise". Let's make it easier. Sensor is a device (oh god, not again...) to collect light. ISO 100 means the Sensor is a lazy guy and it collects light in slower speed. ISO 1600 means the Sensor is a hard working guy and it collects light in faster speed. 

Therefore, a hard working Sensor will collect whatever comes in, even the reflection of dust in the air. Picture with higher ISO speeds will appear white spots and probably you will think the Lens is cover by dust, so you clean it up quickly. Well, you might be correct, but it might just dust in the air.

We are surrounded by dust all the time, you just do not notice. To prove there is dust , turn off your room lights and turn on your torch light. Do you see dust right now?

Someone gonna ask why we need to set higher ISO speeds if it will gain Noise? Do you remember maximum Aperture but still not bright enough in chapter "How does Aperture work?" ? ISO speeds can help you. Higher ISO speeds work well for dark scenes. 

As I told you, a hard working Sensor collects more light. In dark scenes, you can capture a better picture, without Flash, by setting a higher ISO speeds. Also, higher ISO speeds setting save more battery than a Flash. 

This picture is captured in different ISO speeds. If you take a closer look, you will see the ISO500 is actually the clearest and got a the best texture of all. Do not get me wrong, I mean ISO500 is suitable for this picture ONLY because the brightness of environment, the object's colour, the shooting angle and etc might be the factors. Although ISO200 will reduce the noise, it does not capture the best texture. While ISO3200 does not capture the best texture as well. This also proof selecting a suitable ISO speeds will also affect the quality of picture.

However, Do Not Use ISO 6400 and above! Noise increase at this level and the texture is reduced. Most photography at this speeds is more to "document" than actually "use" the picture. 

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