Resolution and the power of pixels

A man walking on a Kelowna pier holding a coffee mug.  Original image is 48 megapixels.

The number of pixels, or rather megapixels, a camera's sensor has defines its resolving power.  Optical resolution is the ability to distinguish two points.  In any image, those two points are determined by a number of factors.  Chief amongst them is the pixel count.

Other factors affecting resolution include lens quality, accuracy of focus, what part of the sensor the area in question resides in, the ISO, nature of exposure (over, under, proper), and finally the points to be distinguished.  Each of these will reflect on the capacity to capture visual information.  Pixel count means very little in an overexposed, blurred, high ISO, object shot at the corner of a frame.  On the other hand, a centrally located object shot with a proper exposure in focus and with a low ISO will likely reveal something significant.  In this situation, pixel count makes a difference.

I shot the above photo with my 135 Plena Z lens on a 48 mp Z series camera.  The Plena provided unparalleled sharpness throughout the frame, even corner shots are more crisp than the central field of most other lenses.  You can see that the mug, although tiny in the original image, has been enlarged with significant details.  The writing is too small to make out, even with extra enhancements.

A 12 mp camera, such as the venerable D300, is capable of capturing images with enough resolution to allow for enlargements (I have done 16x20s with mine) and a fair amount of cropping.  Many crop-sensor cameras and some full-frame ones commonly max out at 20 or 24 mp which is more than enough for the average user.  My full-frame Z body has a 48 mp sensor which is easily enough to either create enormous enlargements or do a significant amount of cropping.  The downside of such a high pixel count is the memory taken for images, RAW or otherwise.  The above photo, shot in RAW, is about 55 MB in size.  It would take 1 gb to store 19 of them.

The upside of such high pixel counts is the ability to crop.  This comes in especially handy in sporting or wildlife photography when you sometimes only have a small area to work with.  You can see in the image below that the ring-billed gull can be significantly enlarged even though it was very small in the frame to begin with.  A nice bonus.

Ring-billed gull photographed with 48 mp camera; bottom image highly cropped.

Thanks for reading.

Eric Svendsen     www.ericspix.com


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