Originally posted by Fogel70 If you want to compare the output of the cameras you need to normalize the output, It's possible to combine both method above, FI by viewing the D800 at 100% and K-5 at 225% (or K5 at 100% and D800 at 44%),
By viewing both at 100% you are not comparing image quality between then, you compare two different crops of the final image. What is the purpose of this comparison? What conclusion can you draw from this comparison?
It is a valid comparison, because you can only use what your output device needs. If the most your output device, printer or screen can handle is 72 DPI, then it doesn't matter if your camera produces 100 dpi, or 300 dpi. People seem to want to keep these discussions isolated from discussions of printer and screen qualities, and that's where the nonsense starts.
Quote: Like comparing a -66 VW Beetle with a new Porsche and it turns out that they are equally fast, when both are driven at 50km/h that is.
Exactly... if what you want to do is drive at 50 km per hour because of traffic, and you have 4 people and baggage to carry, the Porsche is going to really suck. I mean those poor folks are going to be excruciatingly uncomfortable.
They'll be uncomfortable in the Beetle, they'll be deformed by the Porsche.
The problem is, the object in photography is to be able to create output beyond the camera. There is absolutely no benefit to producing "quality" that your output device can't utilize.
Think a screen that's 1280x800.
The absolute most it can display is 1280 distinct lines horizontally and 800 distinct lines vertically. Choosing a camera that will produce 7000 lines horizontally (D810), over one that will produce 6000 (K-3), lines horizontally or even the 5000 line of a K-5 , doesn't increase the resolution of the out put device, and makes no difference at all to the output. It has to reduce both images by factors of 4 or 5. The difference is, digital deals with reduction not enlargement. The problem many photographers have is they think this is still film, where you enlarge your image to display it at a visible size. In digital, we are reducing the image most of the time.
The film equivalent would be taking an 8x10 film image reducing it to 35 film size, and then comparing the images. If what you want is a 35 mm contact sheet type image, shooing the original in 8x10 film offers no advantage. When you reduce the size, you lose all the advantages of the added resolution in the original.
IN film there is that cutoff point where, if all you are going to make is a 4x6, you may as well shoot 35mm instead of 8x10.
In digital it's about 24 inches by 36 inches, for 36 MP over 24 MP as far as I can tell. In digital you have to go really large before you see any benefit. In film sensor size was way more critical, and the difference in sensor size were way more pronounced.
Arguing APS-c against 35mil in digital is like arguing 645 against 6x7 in film. They are both way beyond consumer level in their out put capabilities, and far less than the best out there. For 4x6 or 8x10 prints, they are both extreme overkill.
In any case, I digress.