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Analysis  of  the  "Pixel  Density  Advantage” 

Canon  EOS 7D  Mark II  compared  with  the  Canon  EOS 5D Mark III

Summary of approximate mathematical relationships between image size, pixel density, and pixel size

This summary should be read in conjunction with the full explanatory article that you can see  here. Note that the analysis on this page does not include a discussion of the various complex issues that can arise in practice when estimating pixel density and the pixel pitch or area of individual pixels. It is recommended that you study a detailed technical article if you would like to become familiar with these issues. For example, you may find this  DPR forum discussion  about pixel density and pixel size to be helpful. Therefore, the calculations set out below are presented for the purpose of calculating only a very approximate measurement of pixel density, pixel pitch, and the area of one pixel, which can be used for comparing the approximate mathematical relationships between the pixel density and pixel size of different cameras.

This summary provides an example of how to apply the template that is published  here. In this theoretical template, the reconciliations between the percentages shown for pixel density and pixel size, work out exactly, only because the number of megapixels on the sensor is exactly the same as the image width in pixels, multiplied by the image height in pixels.  In addition, the image width divided by the image height, gives the same answer as the sensor width divided by the sensor height. In the theoretical template, the approximate area calculation for the size of one pixel is exactly equal to the pixel pitch squared. In addition, the approximate area calculation for the pixel density is exactly equal to the linear pixel density squared.

However, in the practical example that follows, the arithmetical reconciliations demonstrated in the template do not work out exactly because of roundings in the specifications used, and also because of the way the effective number of pixels of the cameras is calculated (that is, the image width multiplied by the image height, does not exactly equal the effective number of pixels published for the cameras).

Note: The information below is not designed to provide information about the quality of images or the quality of the cameras, because these are separate issues.

The  Canon EOS 7D Mark II  was announced in September 2014. The  Canon EOS 5D Mark III  was announced in March 2012. This summary shows that, when compared with the Canon 5D Mark III, the Canon 7D Mark II has a linear pixel density that is approximately 53% greater than that of the 5DIII. The approximate “area” relationships for image size, pixel density, and pixel size, are also presented below.

Note: If the (full frame) Canon 5D Mark III had the same pixel density as the (APS-C) Canon 7D Mark II, it would have approximately 52 megapixels, and image dimensions of approximately 8794  pixels x 5863 pixels.

Relevant  Specifications

Canon 7D II: Image dimensions:  5472 pixels x 3648 pixels  (approx. 20.2 million effective pixels); sensor size: 22.4mm x 15.0mm

Canon 5D III: Image dimensions: 5760 pixels x 3840  pixels (approx. 22.3 million effective pixels); sensor size: 36.0mm x 24.0mm

Crop  Factor

Approximately 1.6x  (36.0mm / 22.4mm)

Approximate  Linear  Relationships

Pixel density  (in pixels per linear centimetre)

Pixel density in pixels per linear centimetre = image width in pixels  divided by  width of sensor in centimetres

7DII =    2443  (5472 / 2.24)

5DIII =   1600  (5760 / 3.60)

Pixel Density Advantage: 7DII is approximately 53% greater than 5DIII

Pixel pitch  (in microns)

Refer to the reservations  here  about calculating the "true" width and area of an individual pixel.

Pixel pitch in microns  = width of sensor in millimetres  divided  by  image width in pixels  multiplied by  1000

7DII =  4.09     (22.4 / 5472 x 1000)

5DIII = 6.25     (36.0 / 5760 x 1000)

Relationship: 5DIII is approximately 53% greater than 7DII

Crop an image from 5DIII to the same  field of view  as an image from 7DII

Gain in image width (in pixels) as a result of the above 53% pixel density advantage

Uncropped image width of 7DII   = 5472 pixels

Cropped image width of 5DIII

to same  field of view  as 7DII     = 3584 pixels  (5760 x 22.4 / 36.0)

Relationship: 7DII is approximately 53% greater than 5DIII.

Crop an image from 5DIII to the same  field of view  as an image from 7DII

Gain in comparable widths of print sizes as a result of the above 53% pixel density advantage