Originally posted by Class A Please find that thread and let the person who made that statement know that 16MP is nowhere near enough. When we have 100MP we can start talking.
Morning Class,
I have not tried to go back to find the post, as that would serve no useful function. The desire "that 16MP is nowhere near enough" and that "when we have 100MP ....", need to be based on what is obtainable, practical and useful. Unobtainium is not useful to anyone.
Where I was going was along the lines of diffraction. There are limits (laws of optics) that come in to play as various parameters get jockeyed around, in terms of designing camera systems. I do landscapes, cityscapes and the like. I also dislike hauling around large cameras. The APS-c sensor size as its packaged is pretty optimal for me. I really do not want to go much larger, nor spend a lot more. Nor do I want to dump my glass and start over again.
So back to diffraction. The K5 at 23.7 x 15.7mm yields about 370mm^2 providing a pixel pitch (diameter) of 4.81um. Just for comparison (FF) the D800's pixel pitch is 4.9um. So you start to deal with the Circle of Confusion or Circle of Diffraction.
Using the Cambridge Color site...
Lets look at the Diffraction Limited Aperture
..........................................................................APS-c (16.1MP).......FF (36MP)
Diffraction May Become Visible ..................................f7.2 ........................f7.4
Diffraction Limits Extinction Resolution ........................f9.1 ........................f9.2
Diffraction Limits Standard Grayscale Resolution ........f10.9 ......................f11
OVERALL RANGE OF ONSET .................................f7.2 to f10.9 ...........f7.4 to f11
What this tells me is that at f8 - good for landscapes needing good depth of field, we are already have some diffraction limitations. I believe that its already generally accepted that the APS-c sensors has a hard limit of f16. Another aspect is color. Reds (due to frequency) are more susceptible to diffraction that other colors (i.e., blue). Pentax does have some difficulty with reds.
Playing with the calculator a bit you can see that by increasing the resolution the diffraction just walks down through the aperture ranges. So there are some physical limits that do come into play here.
Bottom line is for me, when considering cost, physical body size and sensor performance (resolution, diffraction, rendering/colors), the K5 holds a lot of value and the K5IIs does add capability. Can you add pixels? - sure you can, however you start to play games with the law of diminishing returns. The question is where is the optimum point in all of this. I don't know, however - I believe that its substantially south of 100MP (in terms of APS-c and FF).
There are lots of additional discussions in this area:
The other aspect to all of this is compromise. Photography is full of compromises. It's a constant game of "whack a mole" - whack it here and it (a problem) pops up over there. Pentax especially has been very successful in terms of increasing the upper limits of ISO, which makes the need for fast lenses less important - other than for shallow depth of field, and diffraction. You can avoid diffraction by using a faster aperture, but depending on what you are shooting your DoF may suffer. That's great, until the size of the glass and it associated expense kicks in. This brings in wide angle. There is a point where you expand the field of view, you start to trade sharpness against the area each pixel needs to represent. The wider the field of view the larger the area each pixel needs to represent, hence the reduction in sharpness Additional resolution will help there - however we are back to the initial point of the post.