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

[kcarney1 at cox.net (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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