Resolution, in digital photography, is about the pixels quantity.  We measure the resolution in megapixel.  One megapixel is one million pixels.  An image equal to a Full HD movie frame is 1920 x 1080 pixels or 2.0736 megapixel.  Typical 22 inches computer monitors show 1920 x 1080 pixels.  The new MacBook Pro 15 inches with Retina display has 2880 x 1800 pixels or 5.2 megapixel.

 

Resolution is important when reading or viewing an image.  If the resolution is not high enough, we can see jagged edge on diagonals.  When printing on a laser printer the standard resolution today is of 600 dots per inches.  Even on the Retina MacBook pro the resolution is less than 300 dots per inches.
As you can appreciate, the requirements associated with printing are usually more important than on-screen.  The majority of images are seen on computer screen that has less than 5.2 megapixels.  This means that a 5.2 megapixel digital camera is plenty enough?  Let’s talk about it:

Benefits of higher resolution images:

  • We often crop images to keep only the interesting part of them.  Cropping is effectively getting rid of pixels.  With high-resolution images you can crop further without impacting on-screen viewing experience;
  • Most images needs sharpening.  Sharpening is more easily done on higher resolution images;
  • You want to print to hang on your wall your preferred pictures? It is usually recommended to have at least 150 to 220 pixels per inches.  This means that a 24 x 36 inches image would need from 19.5 to 42 megapixel;
  • And working on an image to fix blemished for example is easier when the resolution is higher.

So this means that higher resolution is better and could lead to higher quality images when needed.  Should you share your picture on social media only, a 10 megapixel camera is plenty enough.  For commercial use, 20+ megapixel is the norm today.

There is another important aspect to image quality to take into account.  The resolving power of lenses often prevent camera to effectively record on the sensor the all the details possible with their high-end sensors.

Impact of lenses choice on effective resolution:

Body

Canon
EOS 1Ds Mark III

Nikon
D800

Nikon
D800

Resolution (MP)

21

36

36

Lens

Canon
EF 50mm f/1.4 USM

Nikon
AF-S Nikkor 50mm f/1.4G

Sigma
35mm f/1.4 DG HSM A

Measured resolution

15

16

23

Lens Effectiveness

71%

44%

64%

As you can see, to truly benefit from very high-resolution sensors/camera, you have to invest in higher quality lenses.  The Nikon D800 effective resolution with the Nikkor 50mm lens barely surpass the Canon resolution with the equivalent lens even though the D800 resolution is 70 higher than its Canon counterpart.

Don’t forget, from a pure quality point of view, megapixels is only one of the component of pictures quality.  Other elements included Color accuracy, Dynamic range and low light performance.

The included image is a 66 megapixel panorama taken with a Canon 5D Mark II.


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