Is there an effective means to measure the dimensions (length, width, diagonal length) of the effective area of an image sensor in a camera from a photo?

  • What do you mean by "a pixel in a camera"? An actual image sensor in a camera has monochrome receptors with color filters over them that allow it to determine color. Image processing algorithms then use that data to form the final picture you see as a color picture. – AJ Henderson Jun 27 '13 at 14:36
  • @AJHenderson thank you for reminding me of the terminology (it's late here and I have been androiding all day). I will edit the question. – user20509 Jun 27 '13 at 14:57
  • Is EXIF intact? If it is, then the reliable way is to just use the EXIF data. – John Cavan Jun 27 '13 at 15:36

Like many problems with multiple variables, as long as all but one element of an equation is known, then it may be solved for the final variable. If the focal length, focus distance, and size of an object at that distance are known, it would be possible to compute the size of the sensor of the camera that took the photo. That is assuming no post exposure cropping was done.

Likewise, if you know the pixel pitch and resolution of the sensor you could compute the overall dimensions of the sensor.

  • I don't think you can do that just from a photo, without EXIF, though. P&S sensors are very tiny, but often have similar image dimensions to APS-C and so from that data alone, there's no obvious answer to sensor size. If you have EXIF, it usually will tell you a lot of that... – John Cavan Jun 27 '13 at 15:25
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    If you know distance and dimensions of an object in the photo, you can use trigonometry to compute angle of view. If you know angle of view and focal length, you can compute sensor/film dimensions. – Michael C Jun 27 '13 at 15:30
  • Add the math. :) But then you have more than just the photo though as it then depends on how knowledgeable you are about the subject and you'd still likely need EXIF info for the focal length. – John Cavan Jun 27 '13 at 15:34
  • Where exactly does the question state the EXIF info may not be used? But in the case of many fixed focal length cameras, the focal length may be know without EXIF information. – Michael C Jun 27 '13 at 15:49
  • The reason many scientific photographs include a scale (ruler, if you will) is so that objects in the photo can be properly measured by analyzing the photo without the advantage of EXIF information, which of course did not exist during most of the film era (APS did have some rudimentary data encoded on the film). – Michael C Jun 27 '13 at 15:53

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