Originally posted by photoptimist I would certainly agree that size in pixels is a decent first approximation to photograph size as far as cropping, enlarging, and printing are concerned. But the approximation seems to fall apart at the extremes of format differences.
Can one honestly say that a 12 MPix crop from a K-1 or 645Z really be the same "size" as a 12 MPix image from an iPhone? I'd argue that the shallow well depth and much lower DR of the iPhone sensor would surely limit the perceptual resolution of prints in many imaging conditions. The iPhone image simply can't be enlarged as much even if it has the same number of pixels. Especially in regards to resolving shadow details or subtle details in tone, the 12 MPix iPhone image might need to be downsampled to produce a print with the same quality as a 4 or 6 MPix crop from a large-format, large-pixel sensor. The same issue would affect comparisons between newer and older cameras.
Dynamic rage is an issue on some images but not others.
In this image I only used half the dynamic range available. It's a 1:1.7 sensor ( a Q-S1), but I still had lot of DR to play with because of lighting and background conditions. Look at that DoF at 1000mm and ƒ4.
For resolution I resorted to lw/ph, line width per pixel hight not MP. Different systems can achieve different lw/ph with the same MP. For example a K-5 will achieve about 2100 lw/ph with a good lens using Imaging Resources numbers, photozone numbers are higher, but they won't show you the charts so you can judge for yourself). If you have 2000 lw/ph then a 20x 30 inch print will be able to display 100 distinct lines per inch. A K-5 needs 4900x 3200 to achieve that, pretty typical for a Sony sensor. Some of the Canon sensors do almost as good or better with less pixels. SO it's not all about MP.
To use the same reference for a K-1 print you can print to 36 x 54 inches. My screen resolution is 103 pixels per inch, so any image with 100 lw/ph will look about the same as it does on my screen.
But the simple fact is, most of us don't print 20x30 or have screens that are 30 inches wide and 20 inches high at 103 DPI. Whether we are using a K-x a K-5 , a K-1 or a 645z we are capturing resolution we can't display. I'm not talking oversampling, where IQ can be improved, I'm talking about resolution that is lost because there are no out put devices capable of making use of it, unless you print really big.
Someone once suggested to me that my wife's 233 pixels per inch retina (21.5 inch) display would look better than my 103 2650x1440 27 inch screen. It doesn't. The bigger pixels fully utilized look better using the same image, because some of the resolution that would have been lost because it was too small to see has been enlarged enough to be visible.
On a recent test , same image, same lens (DFA 28-105 shot at appropriate distances) her K-5 and my K-1 image looked identical on both screens. We were both throwing out detail to fit the work space. Maybe the K-1 was throwing out more, but what was left seemed to be identical. That's what concerns me about many of these conversations. People are often claiming superior resolution, when in fact, the way they are displaying their images simply means they are discarding more resolution.
They are getting nothing for their money.
Of course as soon as I say that, someone comes in and says "Well I print 40x 60 inch prints all the time so I use every bit of that resolution." and everyone else hides behind their "big print" skirts, as if they do the same.
Folks simply don't want to admit they don't use the resolution they paid for. People like me looking to sell their work will live with the large files because we always want to print at the highest resolution possible. But I don't take 10 images a year out of 30,000 that are worth printing. I'm willing to pay for a K-1, just for those 10. I think a lot of people imagine they are me.
The thing is, we've sold prints from 12 MP, 14 MP and 16 MP cameras. I'm not sure I'm not deluding myself as much as everyone else.
So far it's an untestable theory.
I don't print over 20x30, because I don't think I can sell them.
Of the things that keep me from getting out and selling more prints, resolution was probably the last thing I needed to address.
---------- Post added 02-27-17 at 01:59 PM ----------
Originally posted by Rupert For 99.9% of my wildlife shots I am always sitting in the same chair!
Pardon the sloppy desk and room....Tax time.....you know how that is!
I think the K1 would be better for my wildlife shooting if I could get one of those Tamron or Sigma 150-600 lenses. Maybe they will come around in time and make a Pentax mount?
Regards!
If you have a chair that works why would you change? Once you get things working, don't change anything. Even your socks.