What is the Difference between effective pixels and active pixels of CCD?

Started Aug 20, 2008 | Discussions
ImageChain New Member • Posts: 3
What is the Difference between effective pixels and active pixels of CCD?

Can someone help to clarify that? Thanks.

Chris R-UK Forum Pro • Posts: 19,591
Re: What is the Difference between effective pixels and active pixels of CCD?

From the Learn/Glossary section of this site:
http://www.dpreview.com/learn/?/key=Effective_Pixels
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Chris R

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OP ImageChain New Member • Posts: 3
Re: What is the Difference between effective pixels and active pixels of CCD?

Hi Chris,

thank you. It explains effective pixels. And how about active pixels? I still can not find a answer.

Rgds

Two Truths Veteran Member • Posts: 5,269
Example

I am not entirely sure that they really mean much at all.

For example;

Sony's 12MP CMOS APS-C sensor...
http://www.dpreview.com/news/0708/07082012sony12mpcmos.asp

Total pixels 4428 x 2948 (13.05 MP)
Effective pixels 4320 x 2888 (12.47 MP)
Active pixels 4312 x 2880 (12.41 MP)

Sony's 12MP CMOS dSLR...
http://www.dpreview.com/reviews/sonydslra700/page3.asp

Largest image size 4272 x 2848 (12.22 MP)

I guess that possibly the final image is produced from the "Active pixels" and for some part of the processing it is either cropped or downsampled slightly (losing 40 pixels x 32 pixels). The "Effective pixels" might include a blacked out area, in order to help eliminate background noise.

Random note; the photosites measure 5.49 µm x 5.49 µm, which means that the final images are formed from an area measuring somewhere between 23.4 x 15.6 mm to 23.7 x 15.8 mm.

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sherwoodpete
sherwoodpete Veteran Member • Posts: 7,767
Re: Example

Two Truths wrote:

I am not entirely sure that they really mean much at all.

For example;

Sony's 12MP CMOS APS-C sensor...
http://www.dpreview.com/news/0708/07082012sony12mpcmos.asp

Total pixels 4428 x 2948 (13.05 MP)
Effective pixels 4320 x 2888 (12.47 MP)
Active pixels 4312 x 2880 (12.41 MP)

Sony's 12MP CMOS dSLR...
http://www.dpreview.com/reviews/sonydslra700/page3.asp

Largest image size 4272 x 2848 (12.22 MP)

I guess that possibly the final image is produced from the "Active
pixels" and for some part of the processing it is either cropped or
downsampled slightly (losing 40 pixels x 32 pixels).

Probably cropped. With the old Olympus C5050, the jpeg and image from raw processed using Olympus software had the same size. But processing the raw file in a third-party converter gave an image with a few extra pixels width.

The "Effective
pixels" might include a blacked out area, in order to help eliminate
background noise.

From the example figures you quoted, it seems the "effective pixels" are 4 pixels wider on each side than the "active pixels". So it might be reasonable to assume that allows for the demosaicing of the "active pixel" region.

Regards,
Peter

OP ImageChain New Member • Posts: 3
Re: Example

more or less understood.
Thank you guys.

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