[Leica] OT: Help! How many Megapixels needed?

[Ken Carney]

Here are my thoughts.  First, the sensors on my cameras are 3:2.  If you 
want 16x20" prints (5:4), then some pixels are going to be discarded.  
For example, I have a camera (Canon 5D MkII) that makes a 5616 x 3744 
file (21mp).  To print at 300ppi, that is a 12x18" appx. image.  If I 
want a 16x20 image without resizing, I need to make the short side 16" 
and crop the long side to 20", which gives me a resolution of 234 
pixels.  I try to stay somewhere between 240 and 360, so probably OK 
except there is no further cropping room. Another camera (Fuji XE) makes 
a 4896 x 3264 file (16mp).  The same exercise there gives a print at 
204ppi resolution, maybe OK but still no additional cropping room.  I 
know there are other considerations such as noise, but with prints as 
the goal I would say the analysis is like cash and cubic inches, i.e. 
hard to have too much.

Ken


On 10/28/2015 11:51 AM, Larry Zeitlin via LUG wrote:
>   	Here is a question discussed at a recent photo show. I had no good answer.
> 	
> 	When I first got involved in digital photography almost two decades ago I was advised by engineers at the Kodak research lab that all of the information on a 35mm Kodachrome slide could be contained in 13.5 megapixels. They felt that it would take almost a century to reach that point. (Most of those engineers are now looking for other jobs.) Remember that the first antediluvian digital cameras had only .3 megapixels of resolution. Film, they said, would be safe for many years. That 13.5 megapixel estimate seemed to take on a life of its own. The 4/3s format as finally released was 14 megapixels (now 16 Mp.) and the Leica M8 and first DSLRs were content with less. My first digital Leica had a 1.3 megapixel sensor. I have owned cameras with 3,5 Mp, 5 Mp, 10 and 12 Mp, and 16 Mp. All produced very good results to the naked eye. Admittedly I didn’t use a magnifying glass to explore the details of the image. But then who does?
> 	Now cameras are marketed with 24, 32, and 64 megapixel sensors. Even the iPhone has 8 megapixels. Does it make any difference or is it simply a marketing tool. Theoretically visual quality should improve as the square root of the megapixel count but the electrical complexity of the computation and the display requirements are directly proportional to the pixel count of the sensor. Even Apple, a company that never backed away from complex systems, needs only 5.5 megapixels to drive a 27” Thunderbolt display. I view most of the LUG output on a 13” Mac Pro laptop screen and the work appears perfectly adequate.
> 	For people that want to produce 11” x 14” to 16” x 20” prints or publish their work in most consumer magazines, not display gigantic Colorama sized prints from minuscule portions of the frame area, does the number of pixels really matter? Inquiring minds want to know.
> 	Larry Z
>
>
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