Hello everyone! Today I thought you might want to know a little about your image sensor. I don’t know about you; but I find it humorous to find my electronics covered with stickers showing off the manufacturer’s technology in acronyms and quirky names. When you were shopping for a digital camera, did you read the sticker and say, “WOW, this has a CMOS in it”? Beyond that initial reaction did you ever wonder what CMOS meant? Did you also think, “Wow, I can’t believe I said ‘WOW, this has a CMOS in it’”? LOL.
In today’s consumer and professional level cameras, there are two types of sensor technologies. You have the oldie but a goodie CCD which stands for charge-coupled device. Then you have the new kid on the block, the CMOS chip, which is short for Complementary metal-oxide-semiconductor.
Basically, they do the same thing, they convert light (the image) into an electrical signal, they just have a different method to get to the same destination. In fact, both image sensors are cousins to the solar cell.
On both of these sensors, you have millions of elements called photosites. For every pixel there is a photosite to collect and store incoming light into a “well”. So, for example, if you have a 6 megapixel camera, then there are at least 6 million photosites on your sensor.
CCD

A 6 megapixel CCD
The CCD chip was invented in the 1960′s, it has been well developed and used in videocameras, scanners, and fax machines for many years and for a time was the only type of sensor used in digital cameras.
How does it work?
When light is exposed to a photosite, each one builds up an electric charge in proportion to the intensity of the light. The charge from the photosites is collected one row at a time and eventually transferred to a device that converts the analog signal into a digital value.
CMOS
The CMOS sensor has been around since the 60′s too, but wasn’t developed until much later. The process to make one is very much like the manufacturing of microprocessors used in your home computer.
How does it works?
The collection of the light isn’t too different from the CCD chip. CMOS gets it’s name from the process used to convert the light energy to a voltage (electrical charge) and then eventually sent to an analog to digital converter.
What’s the difference?
CCD sensors images have less noise issues than CMOS sensors. Also, on a CMOS, each photosite has additional circuitry next to it, resulting lower light sensitivity. Instead of the light hitting the photo receptors it hits the transistors. To help counter this, CMOS sensors generally require additional chipsets to help optimize picture quality.
A big plus for the CMOS is that it consumes up to 100 times less power than a CCD sensor so you can get a greater amount of battery life; and because they are produced on the same production line as your computer’s silicon processing chips, they are cheaper to produce. CCD’s require special equipment and expensive processes to manufacture the chips.
As far as quality of the image, they both have great results. I couldn’t tell you which is a clear winner.
That’s all for today, thank you for reading and check back every Techie Tuesday. Please leave a comment or ask a questions.
Peter

Peter Pechacek is a photographer and filmmaker in Orlando, Florida. He is new to the blog and will be contributing weekly on Techie Tuesday
9 comments