7/6/13

Photography Classes Lesson 2 - What is a sensor?

Hello, everyone. Welcome! Let's get started on lesson 2. In case you missed lesson 1, you can head over to this link: Photography Classes - Lesson 1

What's is a sensor?


The sensor records light in a set time the light was allowed in when the camera shutter button is pressed, and the recorded light protons transform into informations for the camera's computer. The sensor comes in two types, CMOS (complementary metal oxide semiconductor ) sensor and CCD (charge coupled device) sensor.



There are many debates on which is better, but we just need to know now is that both technology originated for different applications. At our current time, both technologies work just fine for what we need and I will make a whole new posts on each technology later.


The important thing to know about the sensor is it's three qualities: sensor resolution, sensor size, and sensor quality.

  • Resolution. The resolution is just the number of pixels on the sensor of your camera. 1 megapixel is 1 million pixels.  And the higher number count plays a role to the two important parts in photography: Printing and Cropping.
    • Cropping improves composition of the photograph by deleting unwanted pixels on the photograph. Greater the megapixels of the camera the greater flexibilities the photographer can crop unwanted elements in the shot in post (after the photo is shot and on a photo editing software) when the option to crop, or framing, in camera is not available.
    • Printing requires 240 dots per inch(dpi) or 300 dpi to achieve a good standard print quality. Say an image that's 6 megapixels at 2000 x 3000. And if you print at 300dpi, it will yield a maximum 6.67x10" at 300dpi (2000/300 = 6.67, 3000/300 = 10) good quality print. You can upscale the image, but image quality will drop and look pixelated. Why it's 240 and 300 dpi? This have to do with the way many photo papers on the market absorb the ink droplets and how it spreads without contaminating the adjacent drops. My days in publishing, newspaper require 171dpi and magazines wants 600dpi, and varies based on the type of paper it uses, but for the most part, most photo paper prints well at 240 and 300 dpi.

  • Size. The physical size of the sensor affects the way light is capture and how much pixel is can fit, and also these, that I will cover in later posts: crop factor of your lens, depth of field, ISO noise to list a few. The bigger sensor allows more pixels (higher resolution) and more spaced out pixels to capture the light (quality of photos). It's no accident that medium format camera have a better quality pictures than a compact camera.

    • Sensor sizes usually come in a few sizes, but in most cases they are usually "full frame" and APS-C (advance photo system - type C). The full-frame sensor got it's name by the cameras that use a 35mm film strip frame at 36x24mm. In 1908, the still camera industry took advantage of an existing technology, the 35mm film strips used by the motion pictures industry, and the first commercially sold camera used 36x24mm frame film strip. And now that size is the standard frame size for still camera, and the name "full-frame" sensor represent the sensor size of 36x24mm. In 1996, APS film was introduce with smaller size at 24mm, because handling a 24mm film system was much easier than loading a 35mm film. That ultimately cropping tighter what the lenses can see due to it's size. The diagram below will give you a sense how far along we are at with sensor sizes, starting from small to large size sensors.





  • Quality. The sensor quality is the way each pixel reacts to unfavorable lighting conditions such as low light or high contrast lighting. At which, a good quality sensor can produce low noise for the low lights and better dynamic range for high contrast lighting. Many of the new camera these days boast it's high ISO range as many manufactures are focusing on sensor quality, lately.

Now all I have on the sensors. The take away is that you don't need to rush out and get the best camera with the best sensor out in the market today to be serious in photography. All you really need is a camera that you can override the auto-function, and go out and take pictures. All the tech is just icing.

I will cover lenses on my next post. Until then, send me your questions and comments below. I am working on a table of content page very soon so you can follow along and navigate lessons much more faster. I also have some video interviews of working professional photographers coming up, too. So stay with me and sign up for updates.

This is Charlie Wang of www.wangcharles.com, signing out.

Check out my other post on "how did I started going pro in photography?"