I regularly come across this term "Dual Pixel CMOS AF" or "APS HD CMOS" when reading about cameras. So what is this CMOS term? What does it describe about the camera? Is it telling something that it is cropped sensor or full frame?

I have read some articles but none explains clearly these beginner points.

  • \$\begingroup\$ @MattGrum I thought of that, but that question pretty much assumes you already know that "CMOS" is a specific means of manufacturing a sensor - this is the more basic question which is just "errr... what does CMOS mean at all?" \$\endgroup\$
    – Philip Kendall
    Commented Oct 8, 2014 at 15:02
  • \$\begingroup\$ See the definition of CMOS. However, this question is off-topic then here... \$\endgroup\$
    – TFuto
    Commented Oct 8, 2014 at 15:50

2 Answers 2


CMOS is just a type of sensor. The other possible sensor type is CCD, though CCDs are very rarely used in digital still cameras these days. APS refers to APS-c which is the crop sensor. Dual Pixel AF refers to the fact that the sensor has some micro-lensed pixels that perform both an image sensing and a phased detect auto focus role, thus allowing for PDAF while in live view which wasn't possible prior to dual pixel technology. (Phase detect auto focus is an alternative to contrast based auto focus and is faster and better at dealing with moving targets, but used to require an entirely separate sensor and a mirror to redirect the optical path.)

  • \$\begingroup\$ ok. How do know that a sensor is full frame? \$\endgroup\$
    – Amrit
    Commented Oct 9, 2014 at 5:57
  • \$\begingroup\$ @Amritpal Because the sensor measures approximately 36x24 millimeters. \$\endgroup\$
    – Michael C
    Commented Oct 9, 2014 at 6:15
  • \$\begingroup\$ Generally it will be called full frame or 35mm. \$\endgroup\$
    – AJ Henderson
    Commented Oct 9, 2014 at 6:31
  • \$\begingroup\$ @MichaelClark Right, actually I mean when I the read the description of a camera it will say so and so CMOS sensor. but the size won't be mentioned. In that case how do I know whether that camera is full or cropped sensor? \$\endgroup\$
    – Amrit
    Commented Oct 9, 2014 at 6:34
  • \$\begingroup\$ You look at the camera's specifications and see what the size, in millimeters, of the sensor is. \$\endgroup\$
    – Michael C
    Commented Oct 9, 2014 at 6:46

I'm sure somebody more knowledgeable than me will give an extensive answer, but the short answer is: It refers to the technology of the image sensor, see active pixel sensor on Wikipedia.

Roughly speaking, there are two kinds of image sensor technologies used in most digital cameras: CCD or CMOS. The former stands for charge-coupled device, the latter stems from complementary metal–oxide–semiconductor which is a technology for constructing integrated circuits, more details can be found on the Wikipedia links provided.

For a comparison between these two technologies, see for example CCD vs. CMOS.


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